WPCA – AMEREN ESP SEMINAR

Understanding ESP Controls

© 2004, General Electric Company

By John Knapik

GE Proprietary

22

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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33

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

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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

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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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88

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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1111

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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1212

Finding the mA Signal

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1313

Secondary Current – Pulsating DC

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1414

Typical Primary and Secondary Current

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1515

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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1616

Current Limit - mA & KV

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1717

Secondary Voltage Waveforms – True Negative

KVmin

KVpeak

mA

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1818

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

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2020

Older Analog AVC

GE Proprietary

2121

Microprocessor Based

AVC

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2222

• 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 =

+

ee

e

e

ee

e

e

e

e

ee

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ee

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e

e

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+

+

+

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+

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ee eee

e

ee

e e

e e

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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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2525

AVC Cabinet, CLR & T/R Set

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2626

AVC Spark Response

SETBACK

QUENCH FAST RAMP SPARK RATE

SPARK

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2727

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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2828

Proper AVC Response to Sparking

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2929

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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3434

Spit Spark Response - Secondary Current and Voltage Waveforms

Examples of AVC ‘s at a Limit

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3636

AVC SPARK LIMITED – DOING IT’S JOB

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3737

T/R Current Limited with Sparking

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3838

T-R CURRENT LIMITED WITHOUT SPARKING

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3939

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

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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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4646

T/R Set -Low Voltage Junction Box

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4747

Low Voltage Junction Box

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4848

T/R Nameplate

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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

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5050

Voltage Divider

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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

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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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5454

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

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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

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5757

Current Limiting Reactor (CLR)

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5858

Current Limiting Reactor

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5959

Current Limiting Reactor at T-R Set

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6060

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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6161

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

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6262

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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6363

CLR – Waveform Changes with Impedance

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6464

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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6666

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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6767

First Indication

Second Indication

Short

160 480 1200 45

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6868

Close Clearance160 480 1200 45

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6969

Conductive Dust, Outlet Field

160 480 1200 45

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7070

Bad KV Return160 480 1200 45

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7171

Open160 480 1200 45

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7272

Normal Running Condition

160 480 1200 45

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7373

SCRs Not Firing160 480 1200 45

Questions?

Thank You.