t-3 user guide - phoenix geophysics · 1 r e t p a h 2c introduction intended audience 2 summary...

T-3 Current SourceUser Guide

Version 4 June 2013

T-3 Current Source User Guide

Version 4 June 2013

PHOENIX GEOPHYSICS

Printed in Canada on water resistant, tear-proof Xerox® Polyester Paper.

This User Guide was created in Adobe FrameMaker 10.0. Writing and Production: Stuart Rogers.

Copyright 2013 Phoenix Geophysics Limited.

All rights reserved. No part of this Guide may be reproduced or transmitted in any form or by any means electronic or mechanical, including photocopying, recording, or information storage and retrieval system, without permission in writing from the publisher. Address requests for permission to:

Phoenix Geophysics Limited, 3781 Victoria Park Avenue, Unit 3, Toronto, ON Canada M1W 3K5, or [email protected].

Information in this document is subject to change without notice.

SSMT is a registered trademark of Phoenix Geophysics Ltd. T-3, BP24/72, and the Phoenix logo are trademarks of Phoenix Geophysics Limited. All other trademarks referred to in this document are the properties of their respective owners.

i Contents i

CONTENTS

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2About the T-3 Current Source . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Table of applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Controls and gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Table of controls and gauges (legend to Figure 1.3 ) . . . . . . 5Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Important safety information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Major Safety Concerns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

High Power Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Emergency Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Use of Batteries or an MG. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Wet Weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

How to get further information and support . . . . . . . . . . . . . . 8

ii T-3 User Guide ii

Chapter 2: Setting Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Selecting power sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

High-voltage applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Installing a plug on the AC cable. . . . . . . . . . . . . . . . . . . . . . . . . . . 10Low voltage applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table of typical DC input and output values (5Ω load) . . . 11Designing an output loop for TDEM . . . . . . . . . . . . . . . . . . . . 12

Factors affecting loop design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Depth of investigation and geology . . . . . . . . . . . . . . . . . . . 12Loop inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Loop resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Wire gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Damping resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Series resistors for AC and DC input . . . . . . . . . . . . . . . . . . . 13DC input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13AC input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Typical loop sizes and resistances . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table of loop characteristics, DC input . . . . . . . . . . . . . . . . . 14Table of loop characteristics, AC input . . . . . . . . . . . . . . . . . 16

Loop-design formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Loop inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Damping resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Turn-off ramp time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Connecting the cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Connecting the output cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Assuring correct polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Connecting the AC input cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Connecting the DC input cable—BP24 ⁄ 72 . . . . . . . . . . . . . . . . . . 23Selecting a voltage range—BP24 ⁄72 . . . . . . . . . . . . . . . . . . . . . . . 23Supplying transmission voltage from the BP24 ⁄72 . . . . . . . . . . 24Charging the BP24 ⁄ 72 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Connecting the DC input cable—customer-supplied

batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Chapter 3: Using the Internal Timing Source . . . . . . . . . . . . . . . . . . . 27Resetting the control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Setting the output mode and frequency . . . . . . . . . . . . . . . . 28

Setting time domain or frequency domain . . . . . . . . . . . . . . . . . 29Setting non-periodic DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Selecting the initial voltage range. . . . . . . . . . . . . . . . . . . . . . . 30Electrode resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table of maximum current vs. load resistance . . . . . . . . . . . 31Load impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

iii Contents iii

Setting the volt range control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table of load resistance vs. output voltage range. . . . . . . . 32

Transmitting for geophysical applications. . . . . . . . . . . . . . . 32Monitoring input and output voltage . . . . . . . . . . . . . . . . . . . . . . 33Changing parameters during transmission . . . . . . . . . . . . . . . . . 34

Determining the current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Clearing a low current fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Clearing a high current fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Ending the transmission session . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Chapter 4: Using an External Timing Source . . . . . . . . . . . . . . . . . . . . 37Selecting a timing source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Connecting the timing source to the T-3 . . . . . . . . . . . . . . . . . . . 38Resetting the control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Transmitting for geophysical applications . . . . . . . . . . . . . . . 40Ending the transmission session . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Appendix A: Frequency Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Table of time-domain frequencies . . . . . . . . . . . . . . . . . . . . 43 Table of frequency-domain frequencies . . . . . . . . . . . . . . . . 44

Appendix B: Troubleshooting and Clearing Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Resetting the control panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Table of fault indications and resolutions . . . . . . . . . . . . . . . 51

Appendix C: Properties of Stranded Copper Wire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Table of properties of stranded copper wire . . . . . . . . . . . . 54

Appendix D: TDEM Loops: Measured Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

iv T-3 User Guide iv

Loop-design formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Loop inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Damping resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Turn-off ramp time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Appendix E: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

v List of Figures v

FIGURES

1.1 Table of applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.2 T-3 output waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31.3 T-3 top panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41.4 Table of controls and gauges (legend to Figure 1.3 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51.5 T-3 accessories: AC cable, ventilation-hole covers, and spare fuse pack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62.1 Table of typical DC input and output values (5Ω load) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2 Turn-off ramps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.3 Table of loop characteristics, DC input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.4 Table of loop characteristics, AC input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.5 Recommended damping resistance (Ω) vs. loop size (m x m), from measured data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.6 Measured ramp time (μs) vs. loop resistance (Ω) for various square loop sizes and currents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202.7 Schematic showing connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.8 AC cable connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.9 DC cable and Voltage Setting Plug connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.10 DC input cable connections, customer-supplied batteries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263.1 FREQUENCY SELECT and MODE controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.2 Table of maximum current vs. load resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.3 Table of load resistance vs. output voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323.4 Voltmeter with LINE/HV switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

vi T-3 Current Source User Guide vi

4.1 External timing source cable connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39A.1 T-3 output waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42A.2 Table of time-domain frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43A.3 Table of frequency-domain frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44B.1 Table of fault indications and resolutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51C.1 Table of properties of stranded copper wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54D.1 Loop inductance (mH) vs. square loop size (m x m). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57D.2 Measured ramp time (μs) vs. loop inductance (mH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

1 Chapter 1 1

CHAPTER

INTRODUCTION

2 Chapter 1 Introduction Intended audience 2

SummaryThis document is a guide to the Phoenix T-3 Current Source (2002 and later models), and describes equipment installation procedures, safety precautions, and operation. Users should read the entire document before operating the T-3 to ensure that the equipment is used correctly and that the data obtained are of the highest quality possible.

This chapter introduces the T-3, its applications and controls, and safety information.

Intended audienceThis Guide is intended for use by geophysicists and technicians trained in electromagnetic techniques.

About the T-3 Current SourceThe Phoenix T-3 Current Source is a regulated current source intended for use in geophysical applications such as Spectral

Induced Polarization (SIP) or Complex Resistivity (CR), Controlled Source Audio Magnetotellurics (CSAMT), Time Domain and Frequency Domain Induced Polarization (TDIP, FDIP), Phase Induced Polarization, and Time and Frequency Domain Electromagnetics (TDEM, FDEM). Although the T-3 can be used with other manufacturers’ geophysical equipment, it is intended to be used with Phoenix V5, V6, V8, and RXU receivers in the applications shown in Figure 1.1.

Figure 1.1— Table of applications

Application Load type

CSAMT Grounded Dipole

SIP Grounded Dipole

FDIP, Phase IP Grounded Dipole

Resistivity Grounded Dipole

TDIP Grounded Dipole

MulTEM (TDEM) Ungrounded Loop

LowTEM (TDEM) Grounded Dipole

FDEM Wire/Framed Loop

3 Chapter 1 Introduction Input 3

InputThe T-3 can be powered by a single-phase 50Hz or 60Hz motor generator (MG) providing up to approximately 3.5kVA, 200–240 V AC. Alternatively, the T-3 can be powered by a 12V DC supply for the control panel and a separate 12–72V DC supply for the transmission voltage.

OutputThe T-3 is designed to use either a grounded dipole load or an ungrounded loop. Output voltage is selectable in three nominal ranges: 300V, 600V, and 1100 V (or 1000V maximum where required by law). Output power is 2.2kVA maximum, and output current can range from 0.05 A to 9.0 A. Output frequency can be governed by top panel controls and the internal timing source, or by an external device such as the GPS-synchronized Phoenix RXU-TMR™. Using the internal timing source, time-domain frequencies are available from 0.0625Hz (16s) to 32Hz (64 pulses per second); frequency-domain frequencies are available from 0.125Hz (8s) to over 10 kHz. The waveforms and duty cycle are shown in Figure 1.2.

Figure 1.2— T-3 output waveforms

Controls and gaugesFigure 1.3 shows the top panel controls.

Time Domain (50% Duty Cycle)

Frequency Domain (100% Duty Cycle)

One Period

4 Chapter 1 Introduction About the T-3 Current Source 4

Figure 1.3— T-3 top panel

1 2 3 4 5 6

7 8 bl bm bn bo bp bq9

5 Chapter 1 Introduction Controls and gauges 5

Figure 1.4— Table of controls and gauges (legend to Figure 1.3 )

No. Item

1 Frequency selector. Along with 2, sets the value of n that is used in the MODE (3) formulas.

2 Frequency selector and external source selector. Along with 1, sets the value of n that is used in the MODE (3) formu-las. Alternatively, selects an external timing source.

3 MODE selector for Frequency Domain (FD), Time Domain (TD), positive DC (+) or negative DC (–). The value of n in the formu-las is determined by 1 and 2.

4 Power output and reset switch

5 Output current control. Rotate by half-turns, up to 10 full turns in either direction, to adjust output current.

6 External timing source connector

7 Volt range selector

8 Output current ammeter. The reading is meaningful only when transmission is in progress, not when the POWER switch is off.

9 Voltmeter source selector. Toggle to LINE to read input voltage from MG; toggle to HV to read output voltage or input voltage from batteries.

bl Voltmeter. Displays input voltage when not transmitting and output voltage when transmitting.

bm “ON” lamps. Lit during transmission.

bn “LIM” (limit) lamps. Lit if current or volt range exceeds low or high limit.

bo “DRIVE” lamps. Lit alternately at the frequency of the timing source.

bp “HV” (high-voltage output) lamps. Lit alternately at the fre-quency of the output signal.

bq “INTERLOCK” lamps 1 and 2. Lit when a fault has occurred.

Figure 1.4— Table of controls and gauges (legend to Figure 1.3 (cont’d))

No. Item

6 Chapter 1 Introduction Important safety information 6

AccessoriesThe T-3 is shipped with the accessories shown in Figure 1.5. The AC cable has no termination on the motor-generator end. You must purchase and install a connector suitable for your MG. Grounding is not required. Install the ventilation-hole covers in snowy conditions to protect the T-3; remove them in normal conditions to increase air flow.

Figure 1.5— T-3 accessories: AC cable, ventilation-hole covers, and spare fuse pack

Important safety informationSeveral safety features are built into the system, including automatic shutdown in case of open circuits, over- and under-current, and temperature faults.

Major Safety ConcernsThe major safety concerns specific to the operation of the T-3 are:

High Power Output— The output of the T-3 is up to 9A or 1100V. (Where required by law in certain markets, output is limited to 1000V.) This amount of electrical power can cause serious injury or death.

It is important that the cables and electrodes or wire loop used for the survey work be capable of handling the output. Care should be given to proper installation of the electrodes and terminations

Danger! The T-3 is a high-power current source that can cause serious injury or death if mishandled. Various safety features are built into the T-3, but there is no substitute for safe operation. Please read and follow all the safety instructions provided by this documentation.

7 Chapter 1 Introduction Major Safety Concerns 7

so that electrical conductivity and heat dissipation characteristics are adequate.

Appropriate steps should be taken to prevent people and animals from coming into contact with live electrodes or cables:• Only trained personnel should set up or operate the T-3.• Personnel should wear insulating gloves during setup and

operation.• All possible setup operations should be completed before

connecting input power to the T-3.• Ensure the T-3 is powered off before making any adjustments

to the setup.• The crew chief must alert all personnel in the area before

commencing transmission.• Personnel must maintain adequate distance (3 m) from

electrodes and cables during transmission.

Emergency Stop— The T-3 does not require a dedicated emergency stop switch. To stop transmission in an emergency, toggle the POWER switch off. To stop all operation in an emergency, disconnect the input cable at the side of T-3.

Use of Batteries or an MG— The T-3 requires input power supplied by batteries or a motor-generator (MG).

Handle batteries according to the manufacturer’s instructions, particularly regarding safe storage, transport, charging, and connection.

An MG presents its own safety concerns, such as high power output, fuel handling, battery charging, and high sound pressure levels. Consult the documentation for the MG you use and follow all safety precautions.

The sound pressure level of an MG when the engine is running can exceed 110 dB(A) at 1 m. Exposure to this level of sound pressure for even a short time can cause permanent hearing loss. Personnel working close to a loud MG powering the T-3 should wear hearing protection.

Wet Weather— High-voltage equipment should never be operated in wet weather. If the T-3 is operated in winter, care should be taken to prevent snow from entering the ventilation openings: install the ventilation-hole covers supplied with the unit.

Weight— The T-3 weighs approximately 12 kg. Use correct lifting technique, bending the knees and keeping the back straight, when lifting or moving the T-3.

8 Chapter 1 Introduction How to get further information and support 8

How to get further information and supportContact us at:

Phoenix Geophysics Ltd. 3781 Victoria Park AvenueUnit 3Toronto, ON, CanadaM1W 3K5

Telephone: +1 (416) 491-7340Fax: +1 (416) 491-7378e-mail: [email protected]

Web site: www.phoenix-geophysics.com

You are encouraged to register for a log-in ID and password on our Web site. After registering, you can use the Contact Us link in your private area of the site to request technical support or to report problems.

mailto:[email protected] ?subject=User Guide Question

http://www.phoenix-geophysics.com

9 Chapter 2 9

CHAPTER

SETTING UP

10 Chapter 2 Setting Up Selecting power sources 10

SummaryThis chapter explains how to prepare the T-3 for use in the field or laboratory.

Selecting power sourcesThe T-3 can be powered by a motor generator for high-voltage applications, or by one or more batteries or a controlled 12V DC power source for low-voltage or laboratory applications.

High-voltage applicationsFor normal use in high-voltage applications, the T-3 should be powered by a single phase, 50Hz or 60Hz, 200–240 V motor generator (MG). Such MGs are commercially available world wide; however Phoenix can supply one if required.

Typical high-voltage applications requiring an MG include CSAMT, various IP techniques, Resistivity, and LowTEM (all using a grounded dipole) and FDEM and MulTEM (using a loop).

Installing a plug on the AC cableIf you purchase an MG from Phoenix, the AC cable shipped with it has a suitable plug. Otherwise, the AC cable shipped with the T-3 has a connector on the T-3 end only. At the MG end, you must install a multi-pin plug suitable for the MG you are using. The AC cable contains two wires, which must be connected to the two hot output terminals of the MG. Grounding is not required, and polarity is not significant.

To install a plug:

1 Partially disassemble the plug to reveal the internal terminals, and insert it into the MG receptacle.

2 Start the MG and use a voltmeter to determine which two terminals in the connector are hot. The reading should be between 200V and 240 V.

3 Stop the MG, remove the plug, and connect the wires of the AC cable to the two hot terminals, reassembling the plug as required.

Note An MG nominally rated at 240 V typically provides about 240 V without load or 200–220V under load.

11 Chapter 2 Setting Up Low voltage applications 11

Low voltage applicationsThe T-3 can be used for low voltage applications such as TDEM using an inductive loop, or in a laboratory setting for instructional or test purposes. For these applications, power the T-3 with batteries or other DC sources instead of an MG. Use one 12V DC source to power the control panel and a second DC source for transmission input voltage.

Before using your own batteries with the T-3, obtain a DC input cable from Phoenix.

Phoenix offers the BP24 ⁄ 72 Battery Pack, which provides a 12V control voltage and a transmission input voltage selectable from 12 to 72V. Depending on temperature and battery condition, operating capacity ranges upward from 8AH at 36V or 4 AH at 48V.

Battery voltage and capacity limit the practical application to TDEM (MulTEM) using a loop and short measurement times. In these circumstances, net transmission time that consumes power is very short (bear in mind the 50% duty cycle of time-domain techniques). For example, although MulTEM data acquisition takes place over several minutes, the time required to stack 1000 cycles is only 30 seconds, and the power consumption at 10A output is only 0.04AH.

Some internal loss can be expected when using DC input voltages. Figure 2.1 shows examples of typical input and output values with a 5 Ω load.

Figure 2.1— Table of typical DC input and output values (5 Ω load)

Input Voltage Output Voltage Output Current

24 V 18 V 3.6A

36 V 28 V 5.6A

48 V 38 V 7.6A

60 V 50 V 9.0Aa

a.With higher input voltages, the load resistance must be increased to keep the output current below the 9A limit.

Note When operating with DC input for transmission, there is no output current regulation. The VOLT RANGE and CURRENT SET controls have no effect. Output voltage and current are determined by input voltage and load characteristics.

12 Chapter 2 Setting Up Designing an output loop for TDEM 12

Designing an output loop for TDEMIn TDEM surveys, the signal is generated via a square or rectangular wire loop, laid out on the ground in a plane as horizontal as possible. The loop size, input voltage source, desired current, wire gauge, and weight of the wire must all be considered when planning the survey. This section provides information and instructions concerning the output loop.

Factors affecting loop designThis section describes the major factors that affect loop design. For more detailed information, refer to the TDEM chapter of the System 2000.net User Guide.

Depth of investigation and geology— The targeted depth of investigation and the electromagnetic characteristics of the local geology determine the size of the loop required. As a guideline, the maximum depth that can be sounded is approximately equal to the length of the side of a square loop.

Loop inductance— Loop inductance is a function of the size of the loop and the number of turns of wire forming it. Loop

inductance determines the damping resistance required to shape the turn-off ramp. Inductance and total loop resistance together determine the turn-off ramp time and the maximum current achievable.

Loop resistance— Total loop resistance depends on the loop size and wire gauge plus any resistance added in series to keep the output current within limits. Total loop resistance together with loop inductance determine the turn-off ramp time and the maximum current achievable.

Wire gauge— Wire gauge determines loop resistance. For most purposes, AWG #14 is recommended. However, for small loops, AWG #16 is recommended. This thinner wire keeps the output current within limits without the need for resistance added in series. For reference, a table of properties of stranded copper wire is provided in Appendix C.

Damping resistance— Damping resistance in parallel with the output loop affects the shape of the turn-off ramp. The characteristics of the turn-off ramp are critical for data to be

Note Inductance and resistance are used in the calculation of turn-off ramp time for the T-3 (and TXU-30) transmitter. For the T-4 transmitter, inductance and current are used in the calculation.

13 Chapter 2 Setting Up Factors affecting loop design 13

usable. The ramp should have less than one percent undershoot and minimum oscillation. (See Figure 2.2.)

Figure 2.2— Turn-off ramps. 1Too little damping resistance produces too much undershoot and oscillation; 2appropriate damping resistance produces less than one percent undershoot; 3too much damping resistance produces no undershoot or oscillation.

Series resistors for AC and DC input— The requirement for series resistance to keep the output current within limits differs depending on the input power source, wire gauge, and loop size.

To avoid overheating a series resistor, determine the power rating required using the following formulas.

where:

P = power, WI = current, AR = resistance, Ω

= power adjusted for possible transients, W

= power rating of resistor, adjusted for 50% duty cycle, W

DC input— Resistance in series with the output loop is required only for small loops (25 m square) of AWG #14 wire. As shown in Figure 2.3, add a 1 Ω resistor in series with such a loop. A better alternative for small loops is to use AWG #16 wire, in which case no additional resistor is required.

AC input— As shown in Figure 2.4, add a 25Ω resistor in series with a loop of any size.

Phoenix offers an optional resistor-network accessory for TDEM loops. The accessory includes a 900W, 25Ω current-limiting series resistor and a network of damping resistors. The damping resistance is easily configured in 100 Ω increments from 100Ω to 1100Ω.

1

<1%

2 3

P I2R=

PmaxP

0.95----------=

PrPmax

2-----------=

Pmax

Pr


Typical loop sizes and resistancesThe tables that follow show typical loop sizes and the series resistance and damping resistance required. The resulting turn-off ramp time is also shown.

Figure 2.3— Table of loop characteristics, DC input

AWGSquare

Loop(m x m)

Turns Inductance(mH)

Loop Resistance

(Ω)

Added Series Resistance

(Ω)

Total Resistance

(Ω)

Damping Resistance

(Ω)

RampTime(μs)

16 25 1 0.19 1.32 — 1.32 76 91

16 25 2 0.76 2.63 — 2.63 216 182

14 25 1 0.19 0.83 1.0 1.83 76 65

14 25 2 0.76 1.65 — 1.65 216 290

14 50 1 0.41 1.65 — 1.65 136 157

14 50 2 1.6 2.48 — 2.48 377 406

14 75 1 0.68 2.48 — 2.48 198 173

14 75 2 2.7 4.96 — 4.96 559 343

14 100 1 0.92 3.31 — 3.31 249 175

15 Chapter 2 Setting Up Typical loop sizes and resistances 15

14 100 2 3.7 6.62 — 6.62 709 352

14 150 1 1.4 4.97 — 4.97 341 177

14 200 1 1.9 6.63 — 6.63 429 181

14 300 1 3.1 9.94 — 9.94 621 196

14 400 1 4.2 13.3 — 13.3 780 199

14 600 1 6.6 19.9 — 19.9 1095 209

Figure 2.3— Table of loop characteristics, DC input (cont’d)

AWGSquare

Loop(m x m)


Loop Resistance

(Ω)


(Ω)

Total Resistance

(Ω)

Damping Resistance

(Ω)

RampTime(μs)


Figure 2.4— Table of loop characteristics, AC input

AWGSquare

Loop(m x m)


Loop Resistance

(Ω)


(Ω)

Total Resistance

(Ω)

Damping Resistance

(Ω)

RampTime(μs)

16 25 1 0.19 1.32 25 26.32 76 5

16 25 2 0.76 2.63 25 27.63 216 17

14 25 1 0.19 0.83 25 25.83 76 5

14 25 2 0.76 1.65 25 26.65 216 18

14 50 1 0.41 1.65 25 26.65 136 10

14 50 2 1.6 2.48 25 27.48 377 37

14 75 1 0.68 2.48 25 27.48 198 16

14 75 2 2.7 4.96 25 29.96 559 57

14 100 1 0.92 3.31 25 28.31 249 20

14 100 2 3.7 6.62 25 31.62 709 74

14 150 1 1.4 4.97 25 29.97 341 29

14 200 1 1.9 6.63 25 31.63 429 38

14 300 1 3.1 9.94 25 34.94 621 56

17 Chapter 2 Setting Up Typical loop sizes and resistances 17

14 400 1 4.2 13.3 25 38.3 780 69

14 600 1 6.6 19.9 25 44.9 1095 93

Figure 2.4— Table of loop characteristics, AC input (cont’d)

AWGSquare

Loop(m x m)


Loop Resistance

(Ω)


(Ω)

Total Resistance

(Ω)

Damping Resistance

(Ω)

RampTime(μs)


Loop-design formulasThis section describes the formulas used to derive the values in the previous tables. Use these formulas to determine the loop parameters for non-standard configurations.

Loop inductance— Inductance is a function of the size of the loop and the number of turns of wire in the loop:

where:

L = inductance, mHS = length of square loop side, mN = number of turns of wire in the loop

Damping resistance— Required damping resistance is a function of the inductance of the loop. The following formula, derived from measured data, can be used to calculate suitable resistance values:

where:

L = inductance, mHRd = damping resistance, Ω

(See Figure 2.5 on page 19.)

Turn-off ramp time— Ramp time is a function of loop inductance and resistance. The following formula, derived from measured data, can be used to calculate the turn-off ramp time:

where:

Tr = ramp time, sL = inductance, mHRloop = loop resistance, ΩRa = additional series resistance, Ω


L 0.005 S1.127 N2=

Rd 265 L0.752=

Tr 630 L Rloop Ra+ =

19 Chapter 2 Setting Up Loop-design formulas 19

Figure 2.5— Recommended damping resistance (Ω) vs. loop size (m x m), from measured data

10

100

1000

10 100 1000

Loop size (m x m)

Dam

ping

Res

ista

nce

()

Measured


Figure 2.6— Measured ramp time (μs) vs. loop resistance (Ω) for various square loop sizes and currents

10

100

1000

1 10Loop Resistance ( )

Ram

p Ti

me

(μs)

50 m, 2A50 m, 3A50 m, 5A50 m, 8A100 m, 2A100 m, 3A100 m, 5A100 m, 8A200 m, 2A200 m, 3A200 m, 5A200 m, 8A400 m, 3A400 m, 8A

21 Chapter 2 Setting Up Connecting the output cables 21

Connecting the cablesTwo or three cables are required to operate the T-3: one output loop or two output dipole cables, supplied by the user, and either the optional DC input cable or the AC input cable supplied by Phoenix with the T-3. Additional short lengths of cable may be required to connect resistors.

Connecting the output cables

Two high-voltage output terminals (binding posts) are located on the back of the T-3 below the hinge of the lid. The positive terminal is red; the negative terminal is black.

Assuring correct polarity— In TDEM surveys, the polarity of the output loop is important. The lines of magnetic flux travelling downward should be concentrated on the inside of the transmitting loop during each positive pulse. This concentration

occurs when the current flows clockwise in the loop. Position the T-3 on the perimeter of the loop so that you are facing the centre of the loop when reading the meters. The current then runs clockwise through the loop from the black terminal to the red terminal.

To connect the output cables:

1 Strip 2 cm of insulation from the ends of the output cables and from the ends of any short cables needed to connect damping and series resistance. (See Figure 2.7.)

Danger! Even though the input power source may be a battery of relatively low voltage, the output voltage may be as high as 1100 V. Use caution when connecting and disconnecting the loop. Never touch the output terminals when the T-3 is powered.

22 Chapter 2 Setting Up Connecting the cables 22

Figure 2.7— Schematic showing connections. 1T-3; 2optional TDEM resistance accessory; 3output loop.

2 Loosen the T-3 binding post nuts.

3 Connect the damping resistance and series resistance (if used).

4 Wrap the bare wire ends tightly clockwise around the threaded binding posts, ensuring that there are no loose strands.

5 Tighten the binding-post nuts.

Connecting the AC input cableThe AC input cable for high-voltage applications terminates with a keyed two-pin female connector at the T-3 end and a suitable multi-pin male connector at the MG end. (See Figure 2.8.)

Figure 2.8— AC cable connections

1 2

3

23 Chapter 2 Setting Up Connecting the DC input cable—BP24⁄72 23

To connect the AC input cable:

1 Plug the AC cable into the motor generator and start the MG.

2 Find the AC INPUT connector on the right side of the T-3 case, near the bottom.

3 Aligning the slot of the cable connector with the key of the AC INPUT connector, push the cable connector into the T-3 as far as it will go.

Connecting the DC input cable—BP24 ⁄ 72A DC input cable is supplied with the optional BP24 ⁄ 72 Battery Pack for use in low voltage applications. The cable terminates with a keyed four-pin female connector at the T-3 end and a four-pin male connector at the battery end. (See Figure 2.9.) The BP24 ⁄72 supplies the T-3 with both a 12V control voltage and a variable transmission voltage.

To connect the BP24⁄ 72 DC input cable:

1 Find the DC INPUT connector on the right side of the T-3 case, near the top.

2 Aligning the slot of the cable connector with the key of the DC INPUT connector, push the cable connector into the T-3 as far as it will go.

3 Plug the other end of the cable into the BP24 ⁄72 OUTPUT connector.

Selecting a voltage range—BP24 ⁄ 72The BP24 ⁄72 Battery Pack contains six 12V batteries that can be configured in various serial or parallel arrangements using Voltage Setting Plugs. Each plug is internally wired to cross-connect the batteries in a different pattern, yielding maximum voltages of 36 V, 60V, or 72V. A rotary switch in the centre of the BP24 ⁄72 allows selection of an output voltage in 12V increments from 0V to the maximum available for the given plug.

Warning To avoid damage to the T-3, start the motor generator first, before connecting the AC cable to the T-3.

Note Ensure that the BP24 ⁄ 72 is fully charged before use. See “Charging the BP24 ⁄ 72” on page 25.


Figure 2.9— DC cable and Voltage Setting Plug connections

To set the maximum voltage output of the BP24 ⁄ 72:

1 Set the output to 0V by turning the rotary VOLTAGE SELECTION switch to one of the unnumbered positions on either side of the position you intend to use for transmission.

2 Remove the protective cap on the CHARGER INPUT connector by pushing it in and turning it counterclockwise.

3 Remove the protective cap on the Voltage Setting Plug marked with the desired voltage.

4 Fit the Voltage Setting Plug to the CHARGER INPUT connector and tighten the locking ring to hold the plug in place.

The INTERLOCK 1 lamp and the ammeter display on the T-3 light.

Supplying transmission voltage from the BP24 ⁄ 72As soon as a Voltage Setting Plug is installed on the BP24 ⁄72, an unswitched 12 V control voltage is supplied to the T-3. The transmission voltage is supplied according to the position of the rotary VOLTAGE SELECTION switch on the BP24 ⁄ 72. It is marked with values from 12 to 72V, separated by unnumbered, zero-output positions.

To supply a transmission voltage to the T-3:• Turn the VOLTAGE SELECTION switch to a value less than or

equal to the marking on the Voltage Setting Plug.

Note The BP24 ⁄72 must have a Voltage Setting Plug installed, or it will not operate.

25 Chapter 2 Setting Up Charging the BP24⁄72 25

Charging the BP24 ⁄ 72The BP24 ⁄72 charging cable connector contains cross-connects that group the batteries into separate banks to be charged simultaneously. The free ends of the cable connect to the output terminals of the Phoenix-supplied battery charger.

To charge the batteries in the BP24 ⁄ 72:

1 Read and follow the warnings and instructions supplied with the battery charger.

2 Remove the Voltage Setting Plug or protective cap from the CHARGER INPUT connector.

3 Fit the charging cable to the CHARGER INPUT connector and tighten the locking ring to hold the cable in place.

4 Connect the free ends of the charging cable to the four output cables of the battery charger.

5 Plug the charger into a suitable outlet.

Depending on initial state of charge, the BP24 ⁄ 72 should be fully charged in approximately 4–6 hours.

Connecting the DC input cable—customer-supplied batteriesIt is possible to use one or more 12V batteries in series to provide the transmission voltage to the T-3. An optional DC input cable with spring clips on the free ends can be supplied to make these connections. The control voltage should be supplied by a separate 12 V battery. (See Figure 2.10 on page 26.)

Note Do not turn the voltage selection switch to a value higher than the marking on the Voltage Setting Plug. The BP24 ⁄ 72 will still deliver a voltage to the T-3; however, output will not match the switch setting.

Warning To prevent damage to the equipment, do not plug in the battery charger until all other connections have been made.

Note The cable ends with the spring clips are labelled as control or transmission, with + and – indicators. Ensure that the control leads are connected only to the correct polarity of a 12V supply. Higher voltages or reverse polarity will blow the fuse protecting this circuitry.


To connect the DC input cable for customer-supplied batteries:

1 Find the DC input connector on the right side of the T-3 case, near the top. (See Figure 2.9 on page 24.)

2 Aligning the slot of the cable connector with the key of the DC input connector, push the cable connector into the T-3 as far as it will go.

3 Attach the CONTROL lead clips to the positive and negative terminals of a 12 V battery.

The INTERLOCK 1 lamp and the ammeter on the T-3 light.

4 Attach the TRANSMISSION lead clips to the first and last negative and positive terminals of the battery series.

Figure 2.10— DC input cable connections, customer-supplied batteries: 1Control voltage; 2transmission voltage

+– +– +– +–

. . .12V 12V 12V 12V

1

2 12–72V

27 Chapter 3 27

CHAPTER

USING THE INTERNAL TIMINGSOURCE

28 Chapter 3 Internal Timing Resetting the control panel 28

SummaryThe T-3 current source can be operated under the control of its own internal timing circuits, or under the control of an external timing device such as the Phoenix RXU-TMR™, MTU-TXC™, TXD-6™, or MTU-CL™. This chapter explains the operation of the internal timing source. For instructions on using an external timing source, see “Using an External Timing Source” on page 37.

Resetting the control panelAs soon as the T-3 is powered (by either a motor-generator or batteries) it is ready for use; however, as a safety measure, the system starts in an emergency off mode (INTERLOCK). Also, if a

fault occurs during transmission, the system goes into emergency off mode. The Control Panel must be reset before you can continue. The Control Panel must also be reset after you make any adjustments to the transmission parameters.

To reset the Control Panel:• Press and hold the POWER switch OFF for at least 2 seconds.

The INTERLOCK lamp goes out. Changed settings are ready for use.

Setting the output mode and frequencyFrequencies are selectable from the internal timing source of the T-3 in three ranges:

(Time Domain)

and and (Frequency Domain)

where n is an integer from –3 to 14 (frequency domain) or from –3 to 6 (time domain). The frequencies are listed in the tables on page 43 and page 44.

Note The T-3 does not require a dedicated emergency stop switch. To stop transmission in an emergency, simply toggle the POWER switch off. To stop all operation in an emergency, disconnect the input cable at the side of T-3.

Before operating the T-3 in snowy conditions, install the plug-in caps over the ventilation openings to prevent snow from entering.

2n 1–

2n 2 3 2n

29 Chapter 3 Internal Timing Setting time domain or frequency domain 29

Set the parameters using the two FREQUENCY SELECT controls and the MODE control. (See Figure 3.1.)

Figure 3.1— FREQUENCY SELECT and MODE controls

The positions of the two FREQUENCY SELECT controls determine the value of n. They have no effect when transmitting non-periodic DC. The right FREQUENCY SELECT control also determines whether the timing source is internal or external.

The position of the MODE control determines whether the output is non-periodic DC or periodic waveforms for time-domain or frequency-domain soundings. When the internal timing source is

used, the MODE control also determines whether the frequency will be , , or .

Setting time domain or frequency domain

To select a frequency and waveform for TD or FD soundings:

1 Reset the Control Panel.

2 Find in the table on page 43 (time domain) or page 44 (frequency domain) the frequency or period you wish to use, and note the mode setting in the Mode column.

3 Turn the MODE control to the position noted, in either the TD (time domain) or FD (frequency domain) ranges.

4 From the same row of the table, note the value of n.

5 Turn the left FREQUENCY SELECT control to the column containing the desired value of n.

6 Turn the right FREQUENCY SELECT control to the row containing the desired value of n.

Warning Always ensure that the POWER switch is toggled off before making changes to the timing. The T-3 may be damaged if settings are changed while current is being transmitted.

2n 2n 1– 2 3 2n

30 Chapter 3 Internal Timing Selecting the initial voltage range 30


The DRIVE lamps begin flashing at the set frequency.

Setting non-periodic DC

To select non-periodic DC output:


2 Turn the MODE control to – or + .

The – or + DRIVE lamp lights.


Selecting the initial voltage rangeThis section applies only to operation with a motor generator. If DC input is used for transmission, then the output voltage depends upon the input voltage. The VOLT RANGE control has no effect.

Electrode resistanceIn field surveys, you should prepare the grounded dipole so that the electrode contact resistance is as low as possible. Low resistance will allow the maximum output current possible within the system limitations of 9A, 2.2 kW, and 1100V (1000 V where required by local regulations). This is especially important in CSAMT surveys, since the distance between current source and receiver is so large: the transmitted field must be as strong as possible. Figure 3.2 provides examples of maximum current vs. load resistance.

Note In time domain, only the values from –3 to 6 are valid (LOW and VERY LOW ranges). The HIGH range can not be used; setting the frequency select control to HIGH will result in LOW range values being used.

31 Chapter 3 Internal Timing Load impedance 31

Load impedanceIn some techniques, such as CSAMT using a dipole of several kilometres in length, or FDEM using a large loop, the inductance of the load causes the total impedance at upper frequencies to become very high, and output current is correspondingly low. For example, given a 4 km dipole with a total resistance of 20 (wire plus electrode contact resistance), the effective impedance at 8192 Hz is more than 500. The output current may be as low as 2A even at maximum output voltage.

Setting the volt range controlWhen using an MG, you can choose from three output voltage ranges, numbered 1 (low) to 3 (high) on the T-3 control panel.

The correct range depends on the resistance and impedance of the output load and on the desired current, as explained in the previous paragraphs.

To select the correct voltage range:

1 Measure the output load resistance with an analog ohmmeter. (Digital ohmmeters tend to be less accurate.)


3 From Figure 3.3, determine the volt range setting that corre-sponds to the measured resistance and turn the VOLT RANGE control to that setting. If more than one setting is applicable, start with the lower-numbered setting.


Figure 3.2— Table of maximum current vs. load resistance

Load () Output Current (A) Power (W) Volt Range

30 8.5 2200 1

40 7.4 2200 1

Tip When using an ohmmeter with the T-3, it is good practice to measure resistance in both polarities and calculate the average of the readings. This is particularly important when using a long grounded dipole, where the reading is unstable due to radio frequency interference (RFI) or is offset by a DC self-potential.

If no ohmmeter is available, or if the measurement is suspect, follow the instructions for “Determining the current limit” on page 34.

32 Chapter 3 Internal Timing Transmitting for geophysical applications 32

5 Also from Figure 3.3, note the Output Current range that can be expected.

Transmitting for geophysical applicationsHaving selected the mode, frequency and voltage range, you are ready to operate the T-3 using the internal timing source.

To allow proper regulation, do not operate the T-3 above 90% of the maximum current achievable under the given load and frequency. This is especially important in Spectral IP surveys, since the entire frequency scan must be completed without a change in the current.

To transmit for geophysical applications:

1 Start the MG or turn the BP24 ⁄ 72 VOLTAGE SELECTION switch to the desired DC input voltage.

If you are using DC input, the Control Panel is already powered; the cooling fan does not operate in DC mode.

If you are using an MG, the INTERLOCK 2 lamp and the ammeter display light, and the cooling fan starts operating.

2 If the INTERLOCK 2 lamp is lit, reset the Control Panel.

3 Toggle the POWER switch ON.

If a fault is triggered, see “Clearing a low current fault” on page 35 and “Clearing a high current fault” on page 36. If the load resistance allows at least 0.05A to flow, transmission begins. The ON lamp lights and the HV + and – lamps flash alternately in unison with the DRIVE + and – lamps. (At high frequencies, the rapid flashing is perceived as a steady glow.)

Figure 3.3— Table of load resistance vs. output voltage range

Load Resistance () OutputCurrent

(A)a

a.These values are valid at 25° C; output decreases at higher tempera-tures.

MaximumOutput

Voltage (V)

Volt Rangecontrolsetting

Min. SuggestedMax.

30 600 0.05–9 300 1

120 1200 0.05–5 600 2

900 2000 0.05–1.3 1100 3

33 Chapter 3 Internal Timing Monitoring input and output voltage 33

4 If using an MG, turn the CURRENT SET knob by half-turns in either direction to change the current magnitude. (The CURRENT SET knob has no effect when DC input is used for transmission.)

If the desired current is greater than the 90% limit, better results may be obtained by changing the voltage range. See Figure 3.3 on page 32 and follow the procedure under “Changing parameters during transmission” on page 34.

Monitoring input and output voltageUse the built-in voltmeter and the LINE/HV switch to monitor AC input voltage (LINE) and DC input and high-voltage output (HV). (See Figure 3.4.) The meter displays input voltage when not transmitting and output voltage when transmitting with the VOLT METER switch in the HV position.

Figure 3.4— Voltmeter with LINE/HV switch

To monitor the input voltage :• If using an MG, toggle the VOLT METER switch to LINE and read

the input voltage on the voltmeter middle scale x100.• If using a battery pack, toggle the VOLT METER switch to HV and

read the input voltage on the voltmeter top scale x100. (The LINE position of the VOLT METER switch is not used with DC input.)

Note The ammeter reading is meaningful only when transmission is in progress. If the POWER switch is off, the ammeter does not show changes made with the CURRENT SET knob.


To monitor the output voltage during transmission :• If using an MG, toggle the VOLT METER switch to HV and read

the output voltage on the voltmeter top scale x 100. The maximum reading should correspond to the VOLT RANGE control setting. (See Figure 3.3 on page 32.)

• If using a battery pack, toggle the VOLT METER switch to HV and read the output voltage on the voltmeter top scale x100. (Output voltage is the same as DC input voltage. The LINE position of the VOLT METER switch is not used with DC input.)

Changing parameters during transmission

To change any parameter other than current:

1 Reset the Control Panel. Omitting this step may damage the T-3.

2 Change the FREQUENCY SELECT control, the MODE control, or the VOLT RANGE control as required.



Determining the current limitFollow this procedure to determine the practical current limit if:• no ohmmeter is available to assist in setting the voltage range,

or• during normal transmission the current output is unacceptably

low.

To determine the achievable current:


2 Set the FREQUENCY SELECT and MODE controls for 1 Hz FD. (See “Setting the output mode and frequency” on page 28.)

3 Set the VOLT RANGE control to 1.

4 Turn the CURRENT SET knob fully counterclockwise, then approximately 1.5 turns clockwise. (The ammeter display does not change.)

5 Turn the VOLT METER control to HV.


Warning Do not change any control setting except the CURRENT SET knob while the T-3 is transmitting. Damage to the unit may result. Only the CURRENT SET knob can be safely adjusted while the T-3 is transmitting.

35 Chapter 3 Internal Timing Clearing a low current fault 35


If an INTERLOCK fault is triggered, see “Clearing a low current fault” on page 35. If the load resistance allows at least 0.05A to flow, transmission begins. The HV + and – lamps flash alternately in unison with the DRIVE + and – lamps. (At high frequencies, the rapid flashing is perceived as a steady glow.)

8 Turn the CURRENT SET knob clockwise all the way or until the LCD ammeter reading stops increasing. Note the maximum current.

9 Turn the CURRENT SET knob counterclockwise until the LCD ammeter reading is approximately 90% of the maximum current. To allow proper regulation, do not operate the T-3 above this 90% limit.

If the desired current is greater than the 90% limit, repeat steps 1–9, setting the VOLT RANGE control to the next higher number in step 3.

Clearing a low current faultIf a current of at least 0.05A does not flow when the POWER switch is toggled ON, a fault is triggered. The T-3 stops transmitting and

an INTERLOCK lamp and the LIM LOW lamp light. The fault is triggered when the current magnitude or voltage range are set too low for the load resistance. To clear this fault, you will reset the system and then test first with higher settings of the CURRENT SET knob, then if necessary with higher settings of the VOLT RANGE control.

To find the minimum practical current and voltage settings:


The INTERLOCK lamp goes out.

2 Repeat the procedure for “Determining the current limit” on page 34, but turn the CURRENT SET knob an additional half-turn clockwise in step 4 of each attempt.

If the fault still occurs even with the CURRENT SET knob turned to maximum (fully clockwise), then a higher voltage range must be used:


4 Turn the VOLT RANGE control to the next higher position.


6 As before, if the fault recurs, repeat the procedure using a higher current setting on each attempt.


If you end this procedure using maximum settings of the CURRENT SET knob and the VOLT RANGE control without resolving the INTERLOCK fault, there may be another cause. See “Troubleshooting and Clearing Faults” on page 49.

Clearing a high current faultIf current exceeds the allowable limit when the power switch is toggled on, a fault is triggered. The T-3 stops transmitting and an INTERLOCK lamp and the LIM HIGH lamp light. To clear this fault, you will reset the system and then test first with lower settings of the CURRENT SET knob, then if necessary with lower settings of the VOLT RANGE control.

Follow the instructions in the previous section for “Clearing a low current fault”but turn the CURRENT SET knob counterclockwise in each adjustment and set the VOLT RANGE control to the next lower position.

Ending the transmission session

To end a transmission session:


2 Turn off the motor generator or set the BP24 ⁄72 voltage selection switch to an unnumbered position.

3 Disconnect the cables and replace the protective caps on all connectors.

37 Chapter 4 37

CHAPTER

USING AN EXTERNAL TIMING SOURCE

38 Chapter 4 External Timing Selecting a timing source 38

SummaryIn some applications, it may be desirable to use an external timing source to control the transmission. Phoenix offers several such products.

This chapter explains briefly how to operate the T-3 under external control.

Selecting a timing sourcePhoenix offers several external timing sources for different applications.

The RXU-TMR is the most recent addition to the family of timing sources, and contains the most sophisticated software. This timing source is suitable for all controlled-source techniques. Refer to the System2000.net User Guide for complete instructions.

The TXD-6™ can be used for MulTEM surveys with a V5™ or V6™ receiver connected by a cable link. More detail is provided in the V5 and V6 manuals.

The MTU-CL™ can be used for LowTEM and LOTEM surveys to control a continuous time-domain signal from the T-3. In LowTEM, the receiver is operated several kilometres away from the current source, and is also controlled by an MTU-CL; GPS technology ensures synchronization. The MTU-CL is also used in FDEM and optional CSAMT acquisition with the V6 receiver. More detail is provided in the V6 manual.

Phoenix also offers the MTU-TXC™ GPS-synchronized current source controller. Refer to the MTU-TXC User Guide for complete instructions.

Connecting the timing source to the T-3Most timing sources operate in a similar manner, and all connect to the T-3 via the external timing connector on the upper right corner of the T-3 control panel.

A suitable cable is supplied with each timing source. The cable will terminate with a 12-pin military-grade connector at the T-3

Tip We recommend setting up and verifying the operation of the T-3 using the internal timing source before changing to the external controller. Follow the instructions in Chapter 3.

39 Chapter 4 External Timing Connecting the timing source to the T-3 39

end, distinguished by the diamond-pattern of larger pins. (See Figure 4.1.)

Figure 4.1— External timing source cable connection. The end of the cable with the diamond pattern of four larger pins (highlighted with a white outline in the photograph) connects to the T-3.

To connect the timing source to the T-3:

1 At the T-3, remove the protective cap on the external drive connector by pushing it in and turning it counterclockwise.

2 Fit the T-3 cable to the external drive connector and turn the locking ring clockwise until it locks.

3 Connect the other end of the cable to the timing source as instructed in the User Guide supplied with it.

Resetting the control panelAs soon as the T-3 is powered (by either a motor-generator or batteries) it is ready for use; however, as a safety measure, the system starts in an emergency off mode (INTERLOCK). Also, if a fault occurs during transmission, the system goes into emergency off mode. The Control Panel must be reset before you can continue. The Control Panel must also be reset after you make any adjustments to the transmission parameters.


The INTERLOCK lamp goes out. Changed settings are ready for use.

40 Chapter 4 External Timing Transmitting for geophysical applications 40

Transmitting for geophysical applicationsWhen an external timing source is connected to the T-3, the FREQUENCY SELECT controls have no effect except to disable the internal timing source. The external timing source can drive the T-3 at any frequency in the transmitter’s range (DC to 16 384 Hz nominal). However, all the other controls operate in the same way as when using the internal timing source, and the same procedures apply. See the previous chapter for instructions.

To transmit for geophysical applications using the external timing source:


2 With early T-3 units, turn the right FREQUENCY SELECT control to EXT 2; with later T-3 units, turn the control to EXT 1.

3 Turn the MODE control to the TD position for Time Domain or to one of the FD positions for Frequency Domain.

The DRIVE lamps begin flashing at the rate determined by the frequency-stepping table of the external timing source.



Transmission begins, under the control of the external timing source. Note that if the external timing source is preparing to transmit at a very low frequency, there may be a lengthy delay before current is transmitted.

Ending the transmission session

To end a transmission session:


2 Turn off the motor generator or set the BP24 ⁄72 voltage selection switch to an unnumbered position.

3 Disconnect the cables and replace the protective caps on all connectors.

41 Appendix A 41

APPENDIX

FREQUENCY TABLES

42 Appendix A Frequency Tables 42

SummaryThis appendix provides tables of the frequencies transmitted by the T-3 for each setting of the mode control in both time domain and frequency domain. The waveforms are shown in Figure A.1.

Figure A.1— T-3 output waveforms

Time Domain (50% Duty Cycle)

Frequency Domain (100% Duty Cycle)

One Period


Figure A.2— Table of time-domain frequencies

Period (s) Frequency (Hz) Mode n

0.03125 32 TD 6

0.0625 16 TD 5

0.125 8 TD 4

0.25 4 TD 3

0.5 2 TD 2

1 1 TD 1

2 0.5 TD 0

4 0.25 TD –1

8 0.125 TD –2

16 0.0625 TD -3

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–

2n 1–


Figure A.3— Table of frequency-domain frequencies


16 384 FD 14

10 922.667 FD 14

8192 FD 13

5461.333 FD 13

4096 FD 12

2730.667 FD 12

2048 FD 11

1365.333 FD 11

1024 FD 10

682.667 FD 10

512 FD 9

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n


341.333 FD 9

256 FD 8

170.667 FD 8

128 FD 7

85.333 FD 7

64 FD 6

42.667 FD 6

32 FD 5

21.333 FD 5

16 FD 4

10.667 FD 4

Figure A.3— Table of frequency-domain frequencies (cont’d)


2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n


8 FD 3

5.333 FD 3

0.25 4 FD 2

0.375 2.667 FD 2

0.5 2 FD 1

0.75 1.333 FD 1

1 1 FD 0

1.5 0.667 FD 0

2.0 0.5 FD –1

3 0.333 FD –1

4 0.25 FD –2



2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n

2 3 2n

2n


6 0.167 FD –2

8 0.125 FD –3



2 3 2n

2n

49 Appendix B 49

APPENDIX

TROUBLESHOOTING AND CLEARINGFAULTS

50 Appendix B Troubleshooting 50

SummaryThis appendix explains various conditions that may cause faults during operation and provides information to diagnose and remedy them.

Resetting the control panelIf a fault occurs during transmission, the system goes into emergency off mode. The Control Panel must be reset before you can continue. The Control Panel must also be reset after you make any adjustments to the transmission parameters.



Figure B.1— Table of fault indications and resolutions

Indicator Possible Cause(s) Resolution Reset Procedure

INTERLOCK 2 Initial startup condition. This is a normal condition when the T-3 is first pow-ered up.

Reset the Control Panel.

INTERLOCK 2 VOLT RANGE control setting changed while transmitting.

Always reset the Control Panel before changing the VOLT RANGE setting. Otherwise, damage to the T-3 may result.

Reset the Control Panel. Adjust the VOLT RANGE control. Reset the Control Panel.

LIM HIGH Current too high due to short cir-cuit, or VOLT RANGE set too high or CURRENT SET too high.

Correct short circuit, or reduce requested current or turn the VOLT RANGE control to a lower setting. For detailed instructions, see “Clearing a high cur-rent fault” on page 36.


LIM LOW Current too low due to open dipole circuit, CURRENT SET too low, VOLT RANGE set too low, or open DC supply circuit (in battery opera-tion).

Correct open circuits, or increase the requested current, or turn the VOLT RANGE control to a higher setting. For detailed instructions, see “Clear-ing a low current fault” on page 35.


Lamps and ammeter do not function.

DC input voltage is low or absent. Check DC source, cable and connections. N/A


No output (10 A fuse blown).

Short circuit in output load. In bat-tery operation, load impedance too low or input voltage too high.

Correct output loop or dipole short circuit. In bat-tery operation, reduce the input voltage or increase the output impedance.

Disconnect all power sources, open the T-3 case and replace the fuse (located between the AC and DC input connectors).

No output (30 A fuse blown).

Short circuit in output load. Internal component failure.

Correct output loop or dipole short circuit. If no short circuit is present or if problem recurs, contact Phoenix.

Disconnect all power sources, open the T-3 case and replace the fuse (located between the AC and DC input connectors).

Figure B.1— Table of fault indications and resolutions (cont’d)

Indicator Possible Cause(s) Resolution Reset Procedure

53 Appendix C 53

APPENDIX

PROPERTIES OF STRANDED COPPERWIRE

54 Appendix C Copper Wire 54

SummaryThis appendix is provided as an aid to planning and designing output loops for TDEM applications.

Figure C.1— Table of properties of stranded copper wire

Gauge(AWG #)

Diameter(mm)

Cross-section(mm2)

Resistance(Ω/km)

Weight(kg/km)

10 2.555 5.261 3.277 46.77

12 2.052 3.309 5.210 29.42

14 1.628 2.081 8.285 18.50

16 1.291 1.309 13.17 11.63

18 1.014 0.823 20.95 7.317

20 0.881 0.518 33.31 4.602

55 Appendix D 55

APPENDIX

TDEM LOOPS: MEASURED DATA

56 Appendix D TDEM Loop Data 56

SummaryThe formulas given in Chapter 2, “Setting Up”, were derived from both theory and measured data. This appendix shows some of the measurements used.

Loop-design formulasUse these formulas to determine the loop parameters for non-standard configurations.

Loop inductance— Inductance is a function of the size of the loop and the number of turns of wire in the loop:

where:

L = inductance, mHS = length of square loop side, mN = number of turns of wire in the loop

Damping resistance— Required damping resistance is a function of the inductance of the loop. The following formula,

derived from measured data, can be used to calculate suitable resistance values:

where:

L = inductance, mHRd = damping resistance, Ω


Turn-off ramp time— Ramp time is a function of loop inductance and resistance. The following formula, derived from measured data, can be used to calculate the turn-off ramp time:

where:

Tr = ramp time, sL = inductance, mHRloop = loop resistance, ΩRa = additional series resistance, Ω


L 0.005 S1.127 N2=

Rd 265 L0.752=

Tr 630 L Rloop Ra+ =


Figure D.1— Loop inductance (mH) vs. square loop size (m x m). Blue = measured; red = calculated.

0.1

1

10

100

10 100 1000

Loop size (m x m)

Indu

ctan

ce (m

H)

MeasuredCalculated


Figure D.2— Measured ramp time (μs) vs. loop inductance (mH), which is a function of 1loop size

1

61 Appendix E 61

APPENDIX

SPECIFICATIONS

62 Appendix E Specifications 62

Dimensions

40 cm wide x 55 cm high x 20 cm deep

Weight

12 kg

Environmental

Operation: –20°C to 50°C. Lower temperature operation is possible if the ammeter LCD is warmed.

Ammeter

0.5” (13mm) LCD

Voltmeter

Analog, switchable to display output or input voltage

Current regulation

With AC input, output current is regulated internally within ±0.2% for ±10% change in input voltage or electrode impedance

Protection

Overcurrent: 10.2A maximum

Undercurrent: approximately 0.03A

AC Input

Single-phase 50Hz or 60 Hz motor generator, up to approximately 3.5 kVA, 200–240V AC

DC Input

12 V control voltage plus separate 12–72 V transmission voltage

Output voltage

Nominal 300V, 600V, 1100V (1000V maximum where required by law)

Note Operational specifications are valid at 25°C.


Output power

Maximum 2.2 kVA

Output current

0.05A to 9A

Timing options

Internal or external

Frequency domain (square wave) and time domain (square wave, 50% duty cycle) waveforms are available, governed by an internal crystal oscillator with frequency stability of normal ±50ppm

TDEM turn-off time characteristics

Turn-off time into resistive load: approximately 3s

Turn-off time into a 100 m x 100m loop: linear ramp, approximately 100μs

Turn-off time into a 30m x 30 m loop: linear ramp, approximately 10 μs

Frequency range

DC to 16 384 Hz nominal

65 Index 65

INDEX

AAC cable

connector, 10termination, 6

AC inputcable, 22voltage, monitoring, 33

accessories, 6applications

geophysical, 2, 10geophysical (table), 2high voltage, 10low voltage, 11

Bbatteries

customer supplied, 25safety, 7

battery packBP24/72, 11charging, 25

BP24/72battery pack, 11charging, 25

Ccables

AC input, 22BP24/72 charging, 25connecting, 21DC input (batteries), 25DC input, BP24/72, 23output, 21

changing parameters, 34charging, BP24/72, 25clearing faults, 49

high current, 36low current, 35

Complex Resistivity, 2connecting

AC input cable, 22cables, 21DC input cable, 23

external timing source to T-3, 38motor generator, 22output cables, 21

control panel, resetting, 28, 39, 50Controlled Source Audio Magnetotellurics, 2controls

current set, 33, 34DC input, 11

frequency select, 29mode, 28power switch, 28, 32, 40volt meter switch, 33volt range, 30, 31

DC input, 11copper wire, properties (table), 54CR, 2CSAMT, 2

electrode resistance, 30impedance, 31

currentlimit, determining, 34regulation, 32vs. resistance (table), 31

66 Index 66

Ddamping resistance, 13

customized, 18, 56formulas, 18, 56graph, 19

DC, 11DC input

cable, 11BP24/72, 23connections, batteries (figure), 26customer-supplied batteries, 25

voltage, monitoring, 34DC input and output values (table), 11DC output, transmitting, 30determining the current limit, 34duty cycle, 3

Eelectrode resistance, 30e-mail address, Phoenix, 8emergency off mode, 28, 39emergency stop, 7ending the transmission session

external timing source, 40internal timing source, 36

ext 1, 40ext 2, 40

Ffaults

high current, 36low current, 35table, 49

fax, Phoenix, 8FDEM, 2

impedance, 31FDIP, 2formulas, loop design, 18, 56frequency

setting, 28, 29tables, 41valid ranges, 30

Frequency Domain frequencies (table), 44fuses, 52

Ggeophysical applications, 2graph

damping resistance, 19loop inductance vs. size, 57ramp time

vs. inductance, 58vs. resistance, 20

ground, AC cable, 6

Hhearing protection, 7high-voltage applications, 10HV (voltmeter switch), 33

Iimpedance, load, 31input

DC (table), 11voltage, monitoring, 33

interlock 1, 51at startup, 28, 39

internal timing source, 27

Llim high, 51lim low, 51LINE (voltmeter switch), 33load impedance, 31loop

design formulas, 18, 56size and resistance (tables), 14

low current fault, clearing, 35LowTEM, 2low-voltage applications, 11

67 Index 67

MMG see motor generatormonitoring input and output voltage, 33motor generator, 10

connecting, 22motor-generator

safety, 7MTU-CL, 38MTU-TXC, 38MulTEM, 2

Nn, setting value of, 29

Ooscillation in output loop, 13output

cables, 21current (table), 32DC (table), 11duty cycle, 3loop, designing and connecting, 12mode, setting, 28voltage, monitoring, 34waveforms, 3

Pparameters, changing, 34Phase Induced Polarization, 2

Phoenix Geophysics Ltd., contact, 8plug, AC cable installation, 10polarity, AC cable, 10power consumption, MulTEM, 11power rating, series resistance, 13power sources, selecting, 10properties, copper wire, 54protection, hearing, 7

Rramp time

formula, 18, 56vs. loop resistance, graph, 20

regulation, 32resetting control panel, 28, 39, 50resistance

electrode, 30series, TDEM loops, 13vs. current (table), 31vs. output voltage (table), 32

resistor-network accessory, TDEM, 13ringing (oscillation), output loop, 13

Ssafety information, 6selecting

power sources, 10voltage range, 30voltage range—BP24/72, 23

series resistance, TDEM loops, 13

settingnon-periodic DC, 30time or frequency domain, 29value of n, 29volt range control, 31

SIP, 2snow, and ventilation openings, 7sound pressure, 7specifications, 61Spectral Induced Polarization, 2

TTDEM, 2

loopdesign formulas, 18, 56size and resistance (tables), 14

resistor-network accessory, 13TDIP, 2telephone, Phoenix, 8Time Domain Electromagnetics, 2Time Domain frequencies (table), 43Time Domain Induced Polarization, 2timing source

external, 37internal, 27

transmission session, endingexternal timing source, 40internal timing source, 36

transmittingexternal timing source, 40

68 Index 68

internal timing source, 32troubleshooting, 49turn-off ramp time

see ramp timeTXD-6, 38

Uundershoot, turn-off ramp, 13

Vventilation openings and snow, 7volt meter, reading, 33volt range control, setting, 31voltage range

selecting, 30vs. resistance (table), 32

voltage setting plugs, BP24/72, 23

Wwaveforms, 3

time and frequency domains, 42Web site address, Phoenix, 8winter operation, 7

t-3 user guide - phoenix geophysics · 1 r e t p a h 2c introduction intended audience 2 summary...

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