WPCA – AMEREN ESP SEMINAR
Understanding ESP Controls
© 2004, General Electric Company
By John Knapik
GE Proprietary
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CollectionEfficiency(Percent)
99.999.9
99.099.0
80.080.0
0 100 200 300 400 500 600
Efficiency vs. Specific Corona PowerKNOW WHERE YOUR ESP RUNS ON
THE CURVE
Corona Power – Watts/1000 ACFM
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AVC Cabinet, CLR & T/R Set
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Typical SCR-CLR Electrical System
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
GE Proprietary
55
Just Remember, the Primary of a T-R Set is Rated in Units of RMS, the Secondary is in Average
• 400 V AC RMS• 120 A AC RMS• 45 KV DC Average• 750 mA DC Average
Therefore use an RMS Reading Meter to Calibrate the Primary Meters
GE Proprietary
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Iron Vane Movement
RMS
D’Arsonval
Average
Note! How Do You Tell The Difference?
The Meter Scale Distance is not the Same on the RMS Meter.
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Primary Current Meter
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
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Finding the Primary Current Waveform
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Primary Current – A Chopped Sine Wave
Primary Current Waveform - Positive and Negative Half-Cycles = SCR 1 and SCR 2
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Secondary Current Meter
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
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Finding the mA Signal
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Secondary Current – Pulsating DC
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Typical Primary and Secondary Current
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Secondary Voltage Meter
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
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Current Limit - mA & KV
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Secondary Voltage Waveforms – True Negative
KVmin
KVpeak
mA
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Next – The Automatic Voltage Control
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
The AVCAVC
is the BRAINSBRAINS
of the ESP
GE Proprietary
2020
Older Analog AVC
GE Proprietary
2121
Microprocessor Based
AVC
GE Proprietary
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• Control the amount of sparking in the ESP.• If a T/R set is not sparking, then its AVC
should be pushing that T/R set to one of its pre-set, healthy limits (volts, amps, KV, ma, or firing angle).
• I’ll explain what is meant by “healthy” in a minute
The AVC has 2 Jobs to Execute
The AVC has 2 Jobs to Execute…
But how does the AVC know what’s happening in the ESP?
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The mA signal is its eyes!
Positive & Negative Ions =
Charged Particles =
Free Electrons =
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GroundReturn
Leg
Transformer Rectifier Set
Plate(+)
Electrode
KVKV Meter(Precipitator
Voltage)
mA Meter(Precipitator
Current)mA
e
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AVC Cabinet, CLR & T/R Set
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AVC Spark Response
SETBACK
QUENCH FAST RAMP SPARK RATE
SPARK
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Good Initial Settings for an AVC
1. Quench = 1 Full Cycle
2. Fast Ramp = 5 or 6 Half Cycles
3. Setback = 15 to 20%
4. Spark Rate = 30SPM
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Proper AVC Response to Sparking
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Spark Response - Secondary Current Waveform
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Spark Response - Secondary Current and Voltage Waveforms
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Typical Spark Response - mA & KV
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Further Control – A Search Ramp Rate
New Spark Threshold or T/R LimitSearch Ramp
Spark Threshold
POW Setback Slow Ramp (determined by spark rate)
ER
Fast Ramp Quench (Response to Spark)
T I M EINTERRUPTINTERRUPT
PEDESTALPEDESTAL
RAMPRAMPPHASE BACKPHASE BACK
AUTO PRCS FLWRAUTO PRCS FLWR
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Spit Spark Response (mA)
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Spit Spark Response - Secondary Current and Voltage Waveforms
Examples of AVC ‘s at a Limit
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AVC SPARK LIMITED – DOING IT’S JOB
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T/R Current Limited with Sparking
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T-R CURRENT LIMITED WITHOUT SPARKING
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T-R VOLTAGE LIMITED WITH SPARKING
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What is meant by “Healthy Limits?”
• Primary or Secondary Limit is not healthy when accompanied by a Primary Voltage level < 90 VAC or a Secondary level < 12KV. It usually indicates a short circuit.
• Secondary Voltage Limit is not healthy when there is very little Secondary Current. It usually indicates an open circuit.
• Neither condition is aiding in particle capture
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The T-R Set
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
GE Proprietary
4242
Transformer Rectifier (T/R) Set
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4343
Inside T/R Tank
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4444
High Voltage Transformer
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4545
Diode Stack
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T/R Set -Low Voltage Junction Box
GE Proprietary
4747
Low Voltage Junction Box
GE Proprietary
4848
T/R Nameplate
GE Proprietary
4949
The KV Meter
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
GE Proprietary
5050
Voltage Divider
GE Proprietary
5151
SCR’S
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
GE Proprietary
5252
SCR
GE Proprietary
5353
+-
Time
SCRFiringAngle(90°)
PowerOn
ConductionAngle(90°)
Zero Crossings
90°0° 180° 270° 360°
8.33 milliseconds
Typical Sine Wave
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SCR: Low Voltage to T-R Set
Firing Angle 140°Conduction angle 40°
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SCR: High Power to T-R Set
Firing Angle 40°Conduction angle 140°
400
GE Proprietary
5656
The CLR
FiringCircuit
Microprocessor(s)ControlModule
Current LimitingReactor (CLR)
Transformer/Rectifier(T/R) Set
SCR Stack
A
mA
SignalResistor
SecondaryCurrentMaster
PrecipitatorField
SecondaryVoltageMeter
KV
+ +-
PrimaryCurrent Meter
AutomaticVoltage Control
Primary VoltageMeter
VCT
L - 1
L - 2
mA
GE Proprietary
5757
Current Limiting Reactor (CLR)
GE Proprietary
5858
Current Limiting Reactor
GE Proprietary
5959
Current Limiting Reactor at T-R Set
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90° 90°
SCR’s are why CLR’s are Needed
• The diagram would represent the waveform with the SCRs turning on at 90°.
• If this waveform were applied to the T/R set, very inefficient operation would occur.
• Output power from the T/R set would be greatly reduced.
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To increase the efficiency of the T/R set, a device called a CLR (current limiting reactor) is used. A CLR is an inductor. Recall that the property of an inductor is to oppose a change in current. Because of this property, the shape of the current waveform is changed and it starts looking more like a sine wave.
Electrical Basics: CLR
GE Proprietary
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CLR Function
• Limit short circuit current• Shape T/R secondary wave to be more
sinusoidal• Provide proper form factor• Protect SCRs and T/R diodes from steep
current rise• Increase precipitator voltage and current• Not to be confused with air core reactor
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CLR – Waveform Changes with Impedance
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Proper CLR Sizes for Common T/R Sets
All T/R primaries are rated at 400V
PRI Current Sec. Current Minimum(Amps) (mA) (mH)
40 250 13.080 500 6.6
120 750 4.4160 1000 3.3200 1250 2.6 240 1500 2.2
Basic Troubleshooting
GE Energy
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TR Nameplate Values(For this exercise)
Primary Current 160 Amps
Primary Voltage 480 Volts
Secondary Current 1200 mA
Secondary Voltage 45 kV
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First Indication
Second Indication
Short
160 480 1200 45
GE Proprietary
6868
Close Clearance160 480 1200 45
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6969
Conductive Dust, Outlet Field
160 480 1200 45
GE Proprietary
7070
Bad KV Return160 480 1200 45
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Open160 480 1200 45
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Normal Running Condition
160 480 1200 45
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7373
SCRs Not Firing160 480 1200 45
Questions?
Thank You.