ECE 445 – Senior Design

Design Review

Single-Phase AC Motor Drive Module

Suiping Wu

Isaac Wong

2/23/2015

TA: Cara Yang

Contents 1. Introduction .......................................................................................................................................... 3

1.1. Statement of Purpose ................................................................................................................... 3

1.2. Objectives...................................................................................................................................... 3

1.2.1. Goals...................................................................................................................................... 3

1.2.2. Functions ............................................................................................................................... 3

1.2.3. Benefits ................................................................................................................................. 3

1.2.4. Features ................................................................................................................................ 4

2. Design .................................................................................................................................................... 4

2.1. Block Diagram ............................................................................................................................... 4

2.2. Block Description .......................................................................................................................... 5

2.2.1. H-Bridge Inverter................................................................................................................... 5

2.2.2. Gate Driver ............................................................................................................................ 6

2.2.3. Microcontroller ..................................................................................................................... 7

2.2.4. Voltage/Current Sense Circuit .............................................................................................. 7

2.3 Power Supply ................................................................................................................................ 8

2.3.1 Inverter DC Voltage ............................................................................................................... 8

2.3.2 Auxiliary DC Voltage .............................................................................................................. 8

3. Schematic .............................................................................................................................................. 9

4. Stimulation and Test Load .................................................................................................................. 10

5. Control Flowchart ............................................................................................................................... 12

6. Requirement & Verification ................................................................................................................ 13

7. Tolerance Analysis............................................................................................................................... 14

8. Safety and Ethics ................................................................................................................................. 14

7.1 Safety and Protection ................................................................................................................. 14

7.2 IEEE Code of Ethics ...................................................................................................................... 14

9. Cost Analysis ....................................................................................................................................... 15

9.1. Labor ........................................................................................................................................... 15

9.2. Parts ............................................................................................................................................ 16

9.3. Grand Total ................................................................................................................................. 16

10. Schedule .......................................................................................................................................... 17

1. Introduction

1.1. Statement of Purpose

The project is motivated by current research on electronic pole switching induction

machine in the power and energy group. The number of the phases of the current

motor drive and the performance of the current sensing circuitry were traded off due to

budget and time constraints. Furthermore, commercial motor drive evaluation board

and motor drive IC are either expensive, financially unsustainable for multiphase

machine research in particular, or the motor drive does not meet the voltage and

current requirements for the research project. Hence, there is a demand in economical,

highly flexible, high-voltage, high-current motor drive module.

1.2. Objectives

1.2.1. Goals

- Develop a high-voltage high-current single-phase AC motor drive module

- Build three modules and operate as a three-phase motor drive

1.2.2. Functions

- Convert input DC voltage into AC voltage for multiphase motor applications

1.2.3. Benefits

- Provide a template for fast inverter production or remodeling for multiphase

machine

- Isolate faults onto a single board, reduce replacement cost

- Easy reconfiguration to fit machine that operates at a different number of phase

input

1.2.4. Features

- Highly flexible and configurable

A set of modules can function as multiphase and/or multilevel inverter with multiple

phase-level combinations

- Current feedback control can further expand to more robust vector control if

machine parameters are available

2. Design

2.1. Block Diagram

Microcontroller Gate Driver H-Bridge Inverter

Voltage/Current Sense

Control

Feedback

Figure 1: High Level Block Diagram

2.2. Block Description

2.2.1. H-Bridge Inverter

The H-bridge inverter comprises 4 single power MOSFETs. Each inverter leg will have 2 power

MOSFETs driven by a gate driver to switch the MOSFETs on and off. The inverter is designed to

handle up to an input DC voltage of 300V, and an input current of 10A.

Fairchild Power MOSFET FCB20N60F was chosen to be the inverter gates. The drain to source

breakdown voltage and continuous drain current are twice of the maximum input voltage and

current. This provides headroom for the inverter to handle voltage spike and inrush current during

starting. The low gate charge of 75nC allows a lower gate switching current.

Table 2: FCB20N60F Key Parameters

Key Parameters Values

Drain to Source breakdown Voltage

dsV

600V

Continuous Drain Current DI 20A ( 25cT C )

12.5A ( 100 )cT C

Gate to Source Voltage gssV 30V

Gate Threshold Voltage ( )gs thV :5.0Max V

:3.0Min V Static Drain to Source On Resistance

( )ds onR

: 0.15Nom

: 0.19Max

Total Gate Charge ( )g totalQ : 75Nom nC

:98Max nC

Figure 2: H-bridge Inverter

2.2.2. Gate Driver

Silabs isolated gate driver Si8234AD-C-IS take a single PWM signal and outputs two complementary

gate signals to high and low side. Si8234 also offers protection features such as 5V undervoltage

lockout, 5 kVrms isolation and overlap protection.

The critical parameter, peak current, was calculated as the following using the maximum total gate

charge of FCB20N60F power MOSFET and a switching time of 50ns.

( )max arg argg total ch e ch eQ I T

arg98 50ch enC I ns

arg 1.96ch eI A

The charging current using the above method is an average/constant current. To account for the

nonlinearity of gate charging current, the average value found was doubled (i.e. 4A) to ensure a

sufficient current level to turn the gates on.

List of Key Featuress of Si8234:

- High-Side Low-Side gate driver

- Accepts single PWM signal and outputs two complementary gate signals

- 4.0A peak current

- 5V undervoltage lockout

- 5.0 kVrms isolation

- Overlap protection, Programmable deadtime

2.2.3. Microcontroller

The microcontroller will be responsible for sending PWM signal to the gate driver, receiving

feedback signal of voltage and current and adjust the PWM signal accordingly. TI LAUNCHXL-

F28069M LanuchPad features InstaSPIN-MOTION and InstaSPIN-FOC functions. The two features

provide a robust speed and field-oriented control schemes by replacing the hard-to-tune PID

controllers with simple, single-parameter tuning. The 16 PWM channel with 8 in high resolution

make possible of expanding the project in the future from driving a three-phase motor up to a 18-

phase motor.

2.2.4. Voltage/Current Sense Circuit

The current sense circuit comprises of three components, AD8210, AD8274, and LM4140. AD8210

high voltage, bidirectional current shunt monitor has a common-mode voltage of -2V to +65V with a

gain of 20. LM4140 precision micropower low dropout voltage reference output is connected to the

negative input of AD8274 very low distortion, precision difference amplifier, which ensures that

AD8274 input has the same common mode voltage as the AD8210. The positive input of AD8274 is

connected directly to the output of AD8210. AD8274 is powered from ±15 V supplies and is

configured in a non-inverting gain-of-two configuration. The AD8274 takes the difference between

its two inputs and applies a gain of 2. The input-to-output transfer function is determined to be

( 20) 2out shunt shuntV R I

Assuming the shunt peak current is 15 (i.e 1.5 times more than the rated current), the shunt

resistance value is determined by

5 ( 15 20) 2shuntR

8.33shuntR m

10shuntR m

2.3 Power Supply

2.3.1 Inverter DC Voltage

The DC voltage supplied to the inverter serves as the source voltage which will be converted to AC

using PWM modulation. The inverter DC voltage will be provided by two sources depending on the

stage of development. For safety purposes in the early stage of development, Kenwood PD56-10AD

DC power supply will be used to have fully control on input voltage and current level. The power

supply can provide up to 56V and 10A. Once the design has been verified at low DC voltage, the DC

supply voltage will be stepped up to 120V or 240V using the three-terminal ±120V DC main on the

lab benches in the machinery lab.

2.3.2 Auxiliary DC Voltage

The auxiliary +5V, +12, ±15 DC voltages for supplying the gate driver and sense circuit will be

provided by the DC power supplies on lab bench.

3. Schematic

Figure 3: Inverter Bridge and Gate Drive

Figure 4: Voltage and Current Sense Circuit

4. Stimulation and Test Load

A resistor-inductor load will be connected to the output terminal of the inverter to mimic the

electrical characteristics of an induction motor. For testing purposes and financially reasons, no off-

the-shelf inductor will be purchased. Test load will be using 100 mH toroid and 20 ohm power

resistor from the machinery lab. Stimulation results showed the peak current will not excess 10A

with the maximum voltage input of 300V.

Figure 5: Inverter Voltage (Bottom) and Current (Top) Output Waveform at 300 Vdc, 100mH, 20ohm

5. Control Flowchart

Start of Conversion

Execute ADC Conversion

Save Contexts and Clear

Interrupt Flag

Execute the Park and Clarke

Transformation

Execute PID Modules

Execute the ipark and svgen Modules

Execute the Voltage Calc

Module

Execute the ACI_FE and

ACI_SE Modules

Execute the PWM drive

Restore Context

Return

Figure 6: Control Flow Chart

6. Requirement & Verification

Table 3: Requirement and Verification

Description Requirement Verification Points

Power MOSFET FCB20N60F

Blocks a maximum drain-to-source voltage Vds of 300 ± 5V

Apply Vds voltage of 300 ± 5V across drain

and source terminal. Probe drain current.

30

Be able to handle a voltage spike up to 600V

Sustain an operational continuous drain current Id of 10 ± 1A

Apply gate voltage of 5V. Use Kenwood DC

power supply to apply Vds and inject 10 ± 2A

of current for 5 minutes and 20 ± 1A for 5

seconds across a 100W 1ohm power resistor Be able to handle an in-rush current of 20 ± 1A

Gate Driver Si8234

Output a gate signal to turn on the power MOSFET on

Set up the gate driver and MOSFET on a

breadboard. Use waveform generator to

produce a PWM signal. Probe the drain

current of MOSFET.

20

Microcontroller TI LAUNCHXL-

F28069M

Send PWM signal to gate driver Connect microcontroller to gate driver. Send

PWM signal to gate driver, and probe output

signal of the gate driver 20

Adjust PWM signal with current feedback

Voltage and Current Sense Circuit

Sense and level-shift output voltage and current to microcontroller ADC level

Set up a sense circuit on a breadboard with a

10 mOhm resister. Apply a known current

across the resistor. Probe the sensor outputs

and check with the function output

equations.

20

7. Tolerance Analysis

The most vulnerable part of the inverter is the power MOSFET. When both the high-side and low-

side MOSFET of any one inverter leg is switched on, it creates a short to the ground and draws huge

amount of current, and damages the circuit. Therefore, the gate driver has to be thoroughly tested

with the MOSFET before building and controlling the inverter. MOSFET parasitic body diode reverse

recovery occurs during diode switching from the on-state to the off-state. When the MOSFET is off

(gate-source shorted) and no current flow through its body diode, a voltage step with certain dv/dt

is applied across Drain and Source. The result is a displacement current flow through the drain-base

capacitance (CDB), which can turn on the bipolar to result MOSFET failure.

8. Safety and Ethics

7.1 Safety and Protection

This project involves high voltage and high current. All components shall be carefully chosen, and

their maximum ratings shall not be exceeded. All testing shall begin with low voltage and current

level before moving onto high voltage testing. All power supplies must be turned off before making

any changes on the circuit. Exposed conductors shall be shrink-wrapped.

7.2 IEEE Code of Ethics

As a responsible engineer, we oblige to commit ourselves to the highest ethical and professional conduct and ensure our project will not violate IEEE Code of Ethics. The following is from the IEEE Policies, Section 7 - Professional Activities (Part A - IEEE Policies).

1. to accept responsibility in making decisions consistent with the safety, health, and welfare of the public, and to disclose promptly factors that might endanger the public or the environment;

- The inverter will be thoroughly tested at the maximum rated voltage and current.

High Voltage warning sign will be printed on the circuit.

2. to avoid real or perceived conflicts of interest whenever possible, and to disclose them to affected parties when they do exist; - No sponsors nor other affiliated parties are involved in this project.

3. to be honest and realistic in stating claims or estimates based on available data;

- The readings and findings will be reported and documented as the way they are.

4. to reject bribery in all its forms;

5. to improve the understanding of technology; its appropriate application, and potential

consequences;

6. to maintain and improve our technical competence and to undertake technological tasks for others only if qualified by training or experience, or after full disclosure of pertinent limitations;

7. to seek, accept, and offer honest criticism of technical work, to acknowledge and correct errors, and to credit properly the contributions of others; - Any literature, resources, and personals consulted will be fully acknowledge in the final report.

8. to treat fairly all persons and to not engage in acts of discrimination based on race, religion, gender, disability, age, national origin, sexual orientation, gender identity, or gender expression;

9. to avoid injuring others, their property, reputation, or employment by false or malicious action;

10. to assist colleagues and co-workers in their professional development and to support them in following this code of ethics.

9. Cost Analysis

9.1. Labor

Table 4: Table of Labor Cost

Name Hourly Rate [$] Total Invested

Hours

Cost per Engineer [$]

[2.5 x Hourly Rate x Total Hours]

Isaac Wong 30 170 12,750

Suiping Wu 30 170 12,750

Total 340 25,500

9.2. Parts

Table 5: Table of Parts Cost

Item Description Manufacturer Part No Cost [$] Quantity Total Cost

[$]

Microcontroller TI LAUNCHXL-F28069M 30 1 30.0

Power MOSFET FCB20N60F 5.22 16 83.52

Cartridge Fuse 0326010.MXP 1.69 20 33.8

Non-Inverting Schmitt Trigger SN74LVC1G17 1.0 4 4.0

Inverting Schmitt Trigger SN74LVC1G14 0.49 4 1.96

High and Low Side Gate Driver Si8234AD-C-IS 3.33 6 6.7

Voltage/ Current Sensing IC

AD8210 4.56 8 60.0

AD8274 1.05 8 8.4

AD8479 6.59 8 52.72

LM4140 4.53 8 36.24

4-layer Printed Circuit Board - 66.0 1 66.0

Total: 383.34

9.3. Grand Total

Table 6: Table of Grand Total

Section Total [$]

Labor 25,500

Parts 383.34

Grand Total 25883.34

10. Schedule

Table 7: Table of Schedule

Week

Assignment

Responsibility

4 2/9 Finalize Proposal Isaac

Research on microcontroller Suiping

5 2/16

Research and choose parts for hardware Isaac

Prepare design review

Research and choose microcontroller Suiping

Request/ order parts

6 2/23

Finalize design review Isaac

PCB Schematic and layout

Familiarize with the operation of microcontroller Suiping

7 3/2

Finalize PCB layout and place order Isaac

Build test circuit and test with microcontroller Suiping

8 3/9

Solder components on PCB Isaac

Continue testing with microcontroller and debugging controller code

Suiping

9 3/16

Test inverter circuit with microcontroller Isaac

Revise PCB design and place order

Debug controller code Suiping

10 3/23 Spring Break Isaac

Suiping

11 3/30

Solder components on revised PCB Isaac

Test and debug inverter circuit with microcontroller Suiping

12 4/6

Built three inverter circuits Isaac

Prepare for mock presentation

Prepare microcontroller for three phase operation Suiping

13 4/13 Testing and debugging Isaac

Suiping

14 4/20 Prepare for presentation Isaac

Prepare for demo Suiping

15 4/27 Prepare for final paper Isaac

Prepare for presentation Suiping

16 5/4 Finalize final paper Isaac

Check out Suiping