Download - SCADA, P&ID, PLC, VFD and more
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SCADA, P&ID, PLC, VFD and more
Ralph Stevens
CWEA Instructor
702‐659‐0516
Scada Control Room
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PLC
Typical associated wiring
A‐B SLC 500
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What is a PLC?
CPU
Memory
INPUT
OUTPUT
Power Supply
Programming Device
M
L 1 L 2
L 1L 2
Do you know the 5 parts to a PLC?
WB – pg. WB – pg.
Typical Installation of PLCs
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PLC Ladder Diagram
• PLC’s utilize microprocessors to replace relays
• Different “languages” are used to program
• Ladder logic commonly used because of similarity to relay logic
• Similarity makes it easy to transition from Relay Ladder Logic to PLC
Ladder Logic
The PLC Ladder Diagramis similar to Relay Logic
• Sets of “PLC Instructions” are used by the PLC to examine inputs
• PLC then makes a decision whether or not to provide some type of output based on this input
• Interpreting the PLC Ladder tells you:• What inputs the PLC is looking at
• What values the PLC is looking for
• What action (output) PLC will decide upon based on the input values received
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The PLC Ladder Diagram
• The PLC Ladder Diagram is prepared by PLC Programmers
• Typically requires adjustments in the field during startup and
maintenance
• Must be familiar with programming and programming software to
make changes to the ladder diagram and effect PLC Operation
What is the address for this point on the I/O module?
PLC Addressing
I:01/06
WB – pg. 3WB – pg. 3
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Software Addressing
32 22 12 0232 22 12 0232 22 12 0232 22 12 02
0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
I:01/06
Input switch is CLOSED
Input is HIGH
Address I:01/06 is ONE
16 Bit WORD
PLC Addressing
0
WB – pg. 3WB – pg. 3
The PLC program has its own ladder diagram
OUTPUT
M
01
02
03
L 2
L 1
INPUT
01
02
03
L 1
L 2
0102
Logic in CPU
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The 5 Basic Principles of Successful Control Circuit Interpretation
1. Know your basic symbols and have a handy reference.
2. Read top‐to‐bottom; left‐to‐right.
3. Current is just looking for a path to return to source.
4. If the control elements allow current flow through a load; the load operates.
5. Follow the print to see what actions the load performs
when it operates.
Supply
Switch Load
Return
X 1 X 2
W5 P L
1 C R2 P BS T A R T
1 P BS T O P
1 C R
1 C R
7 F U
1 L S
7 T S
1 C R 2 S O L
0 5 1 2
0 5 1 2
0 5 1 2
0 5 1 2
1 0 4 2
1 0 1 3
1 0 0 21 0 0 1
0 5 2 7
0 5 0 4
Relay Ladder Diagram Ladder Logic Diagram
Bit Instructions – (Relay Type)
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Pump Cycles to Maintain Tank Level
Internal BitB:1
B:1
B:1
LO LevelProbeI:1
HI LevelProbeI:2
Fill Pump Motor Coil
O:1
Fill PumpON/OFF SW
I:0
Pump Cycles to Maintain Tank Level
TANK
Low Level Probe
Hi Level Probe
I:1
I:2
PLCO:1 Motor
Starter
480V, 3Ø
Motor
3Ø AC
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Reading and interpreting basic PLC ladder diagrams.
XIC = Examine if CLOSEDXIO = Examine if OPEN
XIC XICStartStop
In 02 In 01 Out 02
MStartStop
Reading and interpreting basic PLC ladder diagrams.
XIC = Examine if CLOSEDXIO = Examine if OPEN
XIC XICStartStop
In 02 In 01 Out 02
MStartStop
True False
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Reading and interpreting basic PLC ladder diagrams.
XIC = Examine if CLOSEDXIO = Examine if OPEN
XIC XICStartStop
In 02 In 01 Out 02
MStartStop
True ?
RUN
Multi‐function Input Terminals(DI1‐DI2)
P3.01
STOPGr PBRed PB
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Basic Variable Frequency Drives
L1 L2 L3
OL
OL
OL
T1
T2
T3
T1
T2
T3
L1 L2 L3
L1
L2
L3
Motor25HP
480Vac Typical 3 Contactor Bypass Option
VFDDrive
Legend:Position A B C
VFD X X
OFF
BY‐PASS X
C
O
N
T
A
C
T
O
R
A
CONTACTOR B
CONTACTOR C
VFD
Contactor
OVERLOADS
BYPASS
OFFIf there is a problem with the Drive it can be By‐passed if the Drive has By‐pass contactors
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Variable Speed Drive
Activity: Draw your own Ladder Diagram
Constant water flow from process
Low Level
High Level
Water Pump
Goal: • Turn on the pump to drain the tank when we reach the high level.
• Turn off the pump when we reach the low level.
• Automatic operation, no start/stop buttons needed.
• E‐Stop button in case of emergencies.
Can you draw a ladder diagram to do this job?WB – pg. 22 WB – pg. 22
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A Possible Solution
High Level Float Switch
Low Level Float Switch
M
M
E‐Stop
Hot Neutral
Drain Pump Motor
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ElectricalDrawings
Construction
Plan ViewsElevations
DetailsOne line
Wiring DiagramSchedules
Control Diagrams
SchematicLadder
Vendor DrawingsPLC Ladder Diagrams
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Why Electrical Fundamentalsfor Print Reading?
• You may be able to read a diagram, but
• you won’t be able to interpret unless you can
• Explain the terminology
• Trace the current flow path
• Understand device and equipment ratings
• Explain basic code requirements and wiring techniques
• Understand how one change can effect several drawings
One‐line Diagrams
• Used in larger commercial and industrial installations
• Indicates the flow path of power throughout the facility
• May encompass several sheets
• Arranged sequentially such that a smooth flow of power throughout the
facility can be followed from one sheet to the next.
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One‐line Diagrams
• Interpretation requires knowledge of symbols and Device Function
Numbers
• first sheet of Electrical Drawings
• Unique symbols and Device Function Numbers used typically identified
• Index of Electrical Drawings
• Numbered as “E‐XX” (“E Drawings”)
Schematic DiagramOverview
Main Power
LadderDiagram
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Relay Operation
CONTROLVOLTAGEINPUT
L2
L1
TOLOAD
SUPPLY
Magnetyoke
Armature
Coil
Stationarycontacts
Movablecontacts
Contactcarrier
L2
Relay Operation
CONTROLVOLTAGEINPUT
L2
L1
TOLOAD
SUPPLY
Magnetyoke
Armature
Coil
Stationarycontacts
Movablecontacts
Contactcarrier
L2
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What switches control this well pump?
Float Switches
MCC T11 –1
Bkr T11–1 1600
LTSTIUV
MCC T11 –2
LTSTIUV
MCC T11 –3
LTSTIUV
SPARE
LTSTIUV
Bkr T11–2 1600
Bkr T11–3 1600
Bkr T11–4 1600
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T1112.47 kV – 480V2500/2800/3100 kVA55°C/ 65°C/FAZ = 5.75%
86 5051
TRIP & LOBkr 5
From Bkr 5
1 CPT 480 – 120V
480V SWGR
HRG
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WB – pg . 5WB – pg . 5
Example Ladder Diagram
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