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SCR/Generator Control

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Table of Contents... ii

SCR/Generator Control Package...1.0

SCR Drive System... 1.1 Generator Unit... 1.2 SCR Unit...1.3 Driller’s Console... 1.4 Transformer Feeder Unit... 1.5 Motor Control Center... 1.6 Drawworks Braking... 1.7 Unique Devices... 1.8 Spare Parts List... 1.9 SCR/Gen Test Procedure... 1.10 Certificate of Compliance... 1.11

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20605-44 REFERENCE DESCRIPTION Engineering & Marine Services (PTE) LTD This document contains proprietary and confidential information

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20605-46 REFERENCE DESCRIPTION Engineering & Marine Services (PTE) LTD This document contains proprietary and confidential information

National-Oilwell Varco

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D257272-1200-MAN-002

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Generator Unit

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Document number D257272-1200-MAN-002 Revision 01

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REVISION HISTORY

01 17.12.2008 Issued For Information BKF NEG KM

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CHANGE DESCRIPTION

Revision Change Description

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TABLE OF CONTENTS 1 GENERATOR UNIT... 4 1.1 Operation Description ... 4 1.2 Specifications ... 6 2 MAINTENANCE... 8 2.1 Testing... 8 2.2 Servicing... 8 2.3 Theory of Operation... 23 2.4 Power Limit Circuit... 43 2.5 AC Ground Fault Detection Circuit... 46 2.6 TROUBLESHOOTING... 46

3 HI-LINE OPERATION... 51 4 REMOVAL & REPAIR ... 54

4.1 Model 1000... 54 4.2 Model 1400... 55 4.3 Model 1861... 56

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1 GENERAT OR UNIT

1.1 Operation Description

The Generator Unit controls the engine/ generator set to develop a constant AC supply. The output of several generators are fed to a common AC bus (refer to Figure 2-1). Each Generator Unit's AC Control Module has an electronic engine governor; a voltage regulator and a circuit breaker (refer to Figure 2-2). The circuit breaker is interlocked with a Protection circuit which automatically trips the breaker for malfunctions such as

over-current, over-voltage, under/over-frequency and reverses power. In addition, a Synchronization Panel is provided with each system to match individual generator frequency and voltage to the bus frequency and voltage.

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1.2 Specifications 1.2.1 Electrical

Table 2-1 lists the electrical specifications of the AC Control Module.

1.2.2 Mechanical

They are mounted in a sheet steel cubicle. Dimensions vary from model to model. A typical Generator Cubicle is 90" H. x 36" D. x 24" W. and weighs ≈2,000 pounds.

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Table 2-1. Electrical Specifications

Many of the electronic circuits associated with generator control are housed in the AC Control Module. The AC Control Module is constructed from 14-gauge steel, and has its own heatsink.

AC CONTROL MODULE SPECIFICATIONS Size 12" High x 12" Deep x 4" Wide

Weight 25 pounds

ELECTRICAL POWER

AC Supply Three phase, 50 Hz. 600 VAC. GENERATOR CIRCUIT BREAKER

Overcurrent The circuit breaker is preset to trip under the following conditions: Amperes required to trip depends on generator KVA rating.

Overvoltage ≈ 1.16 times normal bus voltage, 100 mS delay.

Overfrequency 55 - 56 Hz.

Underfrequency 42 Hz.

Reverse Power Usually -7% to -10% of rated KW. ENGINE GOVERNOR

Regulation 0.5 Hz, steady state.

Response Time One Second. Load Unbalance 5% rated load.

GENERATOR VOLTAGE REGULATOR

Regulation 3% maximum.

Response Time One Second.

Load Unbalance 10%, no load to full load of rated KVARs. Exciter Power 100/200 VDC, 12 Amps maximum. KVAs

are distributed among generators by reactive droop compensation.

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2 MAINTENANCE

This section contains testing and servicing information to assure proper operation of the Generator Unit. TROUBLESHOOTING (later in this chapter) has an explanation of the

various Generator Unit circuits. REMOVAL AND REPAIR (also later in this chapter)

identifies the various generator assemblies.

2.1 Testing

Perform the functional tests given in Tables 2-2 through 2-6 after repairing/replacing any assembly. Perform the Reverse Power Trip and Engine Mechanical Over-speed tests listed in Table 2-4 once a month.

SERIOUS DAMAGE TO THE ENGINE CAN RESULT IF REVERSE POWER AND ENGINE OVERSPEED FUNCTIONS DO NOT FUNCTION PROPERLY.

These are the tables and their titles:

2-2 Engine/Generator Unit Functional Test 2-3 AC Module Functional Tests

2-4 Protection Circuit Functional Test

2-5 Calibration Procedure for Woodward EG-3P and EG-10P Actuators

2-6 Calibration Procedure for Woodward EG-B 10P Actuators Used on EMD Engines

The TEST switch allows a quick check of the systems vital signals. The TEST switch and

the TEST METER are color coded. For example, if the TEST switch is set to the yellow BREAKER TRIP VOLTAGE position, normal condition is indicated by the TEST METER

needle deflecting to the yellow.

2.2 Servicing

Servicing consists of oil change and calibration procedure of the throttle actuator terminal shaft.

2.2.1 Oil Change

The Woodward EG-3P and EG-10P Actuators receive oil from the engine oil supply, so regular engine oil change intervals are sufficient.

The Woodward EG-B 10P Actuator has its own oil supply. Change it every six months under favorable operating conditions. The oil sump holds one U.S. Quart. Refer to the following and the manufacturer's literature.

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The main difference between these models: the EG-B has a Ball Speed governor and self-contained oil supply.

Changing the Oil in the EG-B 10P

1. To drain the oil, unscrew the Drain Cock located in the lower left-hand corner of the front panel.

2. To flush the actuator, add one quart of diesel fuel or kerosene through the Oil Cup located on the top. Run the engine speed up and down by switching the Engine Control switch between IDLE and RUN. After a few minutes, shut the engine off and drain the fluid.

Repeat flushing until the Drain Cock fluid is clean.

3. Drain all the fluid and screw in the Drain Cock. Fill the actuator with one quart of the recommended lubricating oil. Woodward recommends Mobil 1.

IF THE OIL IN THE EG-B 10P ACTUATOR IS NOT CHANGED REGULARLY, IT WILL BECOME CLOGGED WITH GUM AND FAIL.

2.2.2 TERMINAL SHAFT CALIBRATION

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Table 2-2. Engine/Generator Unit Functional Test

ACTION RESULTS

PRELIMINARY

A. Open all the Generat or unit fuses, with

the engine shut down. A. There are no measur able results from this step.

THROTTLE CHECK

A. Disconnect Throttle (+) (TB11-1) and Throttle (-) (TB11-2) (this is TB4 or TB9 in older systems).

Refer to your s ystem prints to determine the terminal strip connections for the Throttle and Exciter.

B. Measure the resistance between the leads to the Throttle to check for open or short circuit conditions.

C. Measure the resistance between each throttle actuator lead and ground. D. Reconnect the throttle leads.

A. There are no meas urable res ults from this step.

B. The resistance should be ≈30 to 36Ω.

C. The reading should be an open circuit reading ( ∞Ω) unless the cable is grounded.

D. There are no meas urable res ults from this step.

EXCITER CHECK

A. Disconnect the Excit er (+) wire from TB11-7 and the Exc iter (-) wire from TB11-8 (this is T B4 or TB9 in older systems).

Refer to your system prints to determine the terminal strip connections for the Throttle and Exciter.

B. Measure the resistance between the leads to the Generator Exc iter to chec k for open or short circuit conditions. C. Check the resistance from each exc iter

lead to ground.

D. Reconnect the Exciter leads.

A. There are no measur able results from this step.

B. The resistance should be 3 to 20 Ω (this depends on generator model).

C. The resistance should be ∞Ω after TB11-8 in the genera tor switch gear is disconnected.

D. There are no measur able results from this step.

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CONTROL CIRCUIT TEST

A. Set the E NGINE CONTROL SWITCH to IDLE.

B. Start the engine and run it at ≈2/3 speed.

C. Using the oscilloscope, check the phas e rotation at the generator stabs.

Figure 2-3. Phase A

Figure 2-5. Phase C

A. There are no measur able results from this step.

B. If the system incorporates HOC (Hands Off Cranking), the HOC batteries supply power to the AC Control Module (it is not

necessary to manually control the engine actuator).

C. The A phase voltage peak (see Figure 2-3) occurs 120° before the B (see Figure 2-4). The B phase voltage peak occurs 120° before the C (see Figure 2-5). Figure 2-6 shows phase rotation.

Figure 2-4. Phase B

Figure 2-6. Phase Rotation Table 2-2. Engine/Generator Unit Functional Test (Continued)

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CONTROL CIRCUIT TEST (CONCLUDED)

D. Close fuses F30, F3 1, F32, F35, F36, and F37 on the input of the AC Regulator Transformer.

On most models, these fuses will be F30 F31, F32, F33, F34, and F35.

E. Check the phase rotation at the AC Control Module pins 512 through 517.

D. There are no measurable result s from thi s step.

E. There are six phase voltages. VAB (pin

512) should have a waveform which is inverse of VBA (pin 513). The inverse

relationship also exists between VBC (pin

514) and VCB (pin 515), and VCA (pin 516)

and VAC (pin 517). VOLTAGE REGULATOR TEST

A. Disconnect wires Gate A+ (Pin 504) and Gate A- (Pin 505).

B. Close the Exciter fuses.

Exciter fuse numbers depend on

model of sy stem (check y our

generator control schematic in your drawing package). The Exciter fuses for the 1400 system are F39 & F40.

C. Observe the generator VOLTMETER.

D. Monitor the signals at Pins 512 through 517.

E. If the results indicated in Steps C and D occur, reconnect the Gate A+ and Gate A- wires.

F. Set the VOLTS ADJUST control to give

a 50% indication on the generator

VOLTMETER.

A. There are no measurable result s from thi s step.

B. There are no measurable result s from thi s step.

C. The voltage should rise to ≥200 VAC, and fall cyclically as K1 (the build- up relay) picks up and drops out.

D. These signals should also rise and drop.

E. There are no measurable result s from thi s step.

F. The VOLTMETER will indicate 300 to 450

VAC.

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ENGINE GOVERNOR TEST

A. Determine the model of your Throttle Actuator. If it is a Wo odward Mo del EG-B 10P, perform Steps B through D. If it is a Wood ward Model EG-3P or EG-10P, skip to Step E.

B. Set the SPEED DROOP control to 0 (Zero).

C. Set the LOAD LIMIT control to MAXIMUM FUEL.

D. Move the SPEED ADJUST knob on actuator to

maximum CW rotation. This represents a

generator frequency of approximately 54 Hz. Slowly rotate the SPEED ADJUST knob on the

actuator CCW until the engine just begins to

slow down.

SLOWING DOWN THE ENGINE BELOW THIS RPM MAY INTERFERE WITH THE AC MODULE’S ABILITY TO PROPERLY CONTROL THE

OPERATION OF THE ENGINE.

E. Set the SPEED ADJ UST control t o somewhat

less than 50% on it's scale indication.

F. Turn the ENGINE CONTROL switch to IDLE

and start the engine.

G. Allow the engine to warm-up for 15 minutes. H. Turn the ENGINE CONTROL switch to RUN.

I. Fine tune the VOLTAGE ADJUST and SPEED ADJUST knobs to achieve 600 VAC at 50 Hz.

J. Turn the ENGINE CONTROL switch to IDLE.

K. Turn the ENGINE CONTROL switch the

engine back to RUN.

A. There are no measurable results from this step. Steps B through F set the various

controls of the Throttle Actuator.

Woodward Models EG-3P and EG-10P do not have these controls and,

therefore, do not require these steps to be performed.

B. There are no measurable results from this step. C. There are no measurable results from this step. D. There are no measurable results from this step.

E. There are no measurable results from this step. F. There are no measurable results from this step. G. There are no measurable results from this step. H. The generator voltage and frequency should

increase as the ENGINE CONTROL switch is moved from IDLE to RUN.

I. The Generator VOLTMETER will indicate 600 VAC. The FREQUENCY meter will indicate 50 Hz.

J. The generator voltage and frequency should decrease to Idle values.

K. The generator frequency should stabilize at 50 Hz within two overshoots.

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Table 2-2. Engine/Generator Unit Functional Test (Continued)

SYNCHRONIZATION CIRCUIT TEST

A. Connect one engine/ generator to the Main AC Bus.

This test only needs to be performed if components in the synchronizing circuit have been changed or if a problem is encountered in synchronization.

B. Proceed to a seco nd/subsequent generator, and following the st eps indicated in the previous s ections of the test, adjust it s controls to develop 600 VAC at 48 Hz.

C. Connect an AC Volt meter, switched to read 600 VAC, between the oncoming

generator's stab A phas e and the Main AC Bus stab A phase.

D. Adjust the generator’s frequency to 50 Hz, so that it slowly goes in and out of

synchronization with the Main AC Bus. Observe the Volt meter, the

SYNCHROSCOPE, and SYNC LIGHTS.

E. Close the oncoming generator’s circuit breaker when sync occurs.

Synchronization between the Main AC Bus and the oncoming generator has occurred when the needle of the SYNCHROSCOPE is points vertically, the SYNC LIGHTS are off, and a Simpson Model 250 (or equivalent) Volt Ohm Meter (VOM) connected to the top and bottom of the Main AC Circuit Breaker indicates minimum voltage.

A. There are no measurab le resu lts from this step.

GENERATOR CIRCUIT BREAKERS WILL NOT CLOSE UNTIL

SYNCHRONIZED WITH THE MAIN AC BUS. DO NOT CLOSE ANOTHER GENERATOR’S CIRCUIT BREAKER UNTIL THE SYNCHROSCOPE AND SYNC LIGHTS HAVE BEEN CHECKED FOR PROPER OPERATION.

B. The pointer of the SYNCHROSCOPE will

turn counterclockwise. The SYNC LIGHTS

will be dimly illuminated.

C. There are no measurab le resu lts from this step.

D. The pointe r of the SYNCHROSCOPE will

turn clo ckwise o r co unterclockwise. The

SYNC LI GHTS will alternat ely di m and

brighten.

E. The generator’s circuit breaker will not close if proper synchronization has not been

achieved. The KVAR meters of all generators

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Table 2-2. Engine/Generator Unit Functional Test (Continued)

LOAD DISTRIBUTION TEST

Five separate tests comprise the Load Distribution Test:

• KVAR Sharing Test. • KW Sharing Test.

• Master/Slave Sharing Test. • Engine/Generator Idle-Run Test. • Load Testing Engine/Generator Test.

KVAR Sharing Test

A. Balance the KVARs by using the VOLTS ADJUST knob of the Gener ator Control Cubicle that has the lowest reading KVAR.

KW Sharing Test

A. Connect all engine/generator sets to the Main AC Bus.

B. Make assignments to provide ≈60% KW Load.

Master/Slave Sharing Test

A. Connect all the system generators to the Main AC Bus. The KW and KVAR reading

of each connected engine/generator set should be about the same.

B. Disconnect Generator 1 from the Main AC Bus.

C. Disconnect Generator 2 from the Main AC Bus.

D. Reconnect all generators to the Main AC Bus.

A. Watch the KW and KVAR readings while

the system load is changing. The generator readings should be about the same.

B. The KW METERS of all engine/generators

should read the same and track together as the KW Load varies.

A. Observe that only the master generator

SPEED ADJUST dial has an e ffect on the

speed of all the engines on the lines. Verify that the lowest numbe red onlin e generator controls all other online generators.

B. Verify that with Gener ator 1 off the Main AC Bus, Generator 2 controls all other

connected generators

C. Verify that with Gener ators 1 and 2 off the Main AC Bus, Generator 3 controls all other connected generators.

D. There are no measurable results from this step.

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Table 2-2. Engine/Generator Unit Functional Test (Concluded)

LOAD DISTRIBUTION TEST (Concluded) Engine/Generator Idle-Run Test

A. Start an engine/genera tor set and run it at

IDLE. Follow the recommended warm up

time specified by the engine/generator set manufacturer.

B. Put the ENGINE CONTROL switch to RUN

and adjust the SPEED ADJUST

potentiometer to 50 Hz.

C. Put the ENGINE CONTROL switch to IDLE.

D. Put the ENGINE CONTROL switch to RUN. Load Testing Engine/Generator Test

A. After performing the Engine/Generator Idle-Run test, connect the engine/generator to the Main AC Bus.

B. Connect a load (such as a tank of salt water) to the Main AC Bus.

B. The generator voltage and frequency should increase as the engine goes from IDLE to RUN speed.

C. The generator voltage and frequency should decrease to the idle value.

D. The generator frequency should stabilize a t 50 Hz. within two overshoots.

B. Observe the Engine/Generator's KW METER and compare the reading to the

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Table 2-3. AC Control Module Functional Test

PRELIMINARY

A. Inspect the AC Control Module wiring harness for incorrect and/or loos e connections.

B. Turn on the Generator unit.

A. Fix any incorrect or loose connections.

B. The Generator RUN light and the AC

Control Module front panel POWER ON light

will illuminate.

POWER SUPPLY CHECK

A. Measure the voltage at the following points: Terminal Pin 502 Terminal Pin 503 Terminal Pin 507 Terminal Pin 508 Terminal Pin 546 Auxiliary Board Pin 24

A. The voltage should be: +16 VDC -16 VDC -160 VDC +160 VDC +11 VDC -11 VDC

FREQUENCY DEMODULATOR TEST

The Frequency Demodulator Circuit is used to develop a speed feedback signal. This signal is necessary for diesel engine speed regulation. The six AC phases from the AC Regulator Transformer are processed by the Demodulator Circuit into the Frequency Demodulator Output Waveform. The Frequency Demodulator Output Waveform is converted by the AC Control Module circuit into the Frequency Feedback Signal which can be measured at TP19 of the AC Control Module. The Frequency Feedback Signal will be -2.5 VDC at the system's proper operating frequency.

The appearance of the Frequency

Demodulator Output Waveform w ill

NOT appear the same if different oscilloscope adjustments are used. Therefore, use the suggested settings for viewing the waveform.

Field calibration of this circuit is difficult and not recommended.

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Table 2-3. AC Control Module Functional Test (Continued)

FREQUENCY DE MODULATOR TE ST

(CONCLUDED)

A. Check TP5 for the Frequency Demodulator Output Waveform in the Unit Under Test.

If desired, you can compare the waveform of the Unit Under Test with the waveform of a known fully

functional unit.

A. The wavef orm should be lik e the one shown in Figure 2-7.

Figure 2-7. Frequency Demodulator Output Waveform

CURRENT DEMODULATOR TEST

A. Check the following pa rameters at the given location:

PARAMETER LOCATION

IREAL Auxiliary Board Pin 5

IREACTIVE Auxiliary Board Pin 6

A. Since there is no current flow, the measured voltages will be:

Zero (0) Volts. Zero (0) Volts

VOLTAGE REGULATOR TEST

A. At run speed, rotate the VOLTS ADJUST

control knob to its center position. B. Monitor Test Point 12.

C. Monitor the VOLTAGE REFERENCE signal

at AC Control Module Pin 551.

B. The voltage should be ≈-92 VDC @ 600 VAC.

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Table 2-3. AC Control Module Functional Test (Concluded)

VOLTAGE REGULATOR TEST (CONCLUDED)

D. Monitor the EXCITER FIELD SUPPLY FIRING PULSE at AC Control Module Pin 504

(GATE A+).

D. The EXCITER FIELD SUPPLY FIRING PULSE waveform should look like the one in

Figure 2-8.

Figure 2-8. Exciter Field Supply Firing Pulse Waveform

FREQUENCY REGULATOR TEST

A. Rotate the SPEED ADJUST control knob t o

its center position.

B. Monitor the SPEED REFERENCE signal at

AC Control Module Pin 547.

C. Monitor the engine/generator's speed.

B. The voltage should be +4.0 to +6.0 VDC. C. It must fall within the normal operating speed range of the engine/generator.

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Table 2-4. Protection Circuit Functional Test

ACTION _RESULTS

NO PULSE TRIP

A. Connect an engine/generator set to the Main AC Bus.

B. Disconnect TACH S IGNAL lead at AC

Control Module Pin 526.

C. Test all remaining engine/generator sets by repeating Steps A and B.

This test applies only to systems equipped with a Tachometer Pulse Pickup circuit.

A. The Generator ON LINE light will illuminate.

B. The Generator Circuit Breaker will trip off line, the engine will die, and the Generator

ON LINE light will extinguish.

C. Results will be as shown in Steps A and B.

REVERSE POWER TRIP

A. Connect a generator to the Main AC Bus. B. Connect a jumper between AC Contr ol

Module Pins 533 and 545 (this is the Throttle Output).

Connecting this jumper between pins 533 and 545 will cause a reverse power condition.

C. Once the Generator Circuit Breaker trips off line, remove the jumper between Pins 533 and 545.

B. The Generator Circuit Breaker

corresponding to the gener ator will trip off line in eight to 10 Seconds.

C. The engine will return to RUN speed and

the Generator Circuit Breaker will be in the OFF

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Table 2-5. Calibration Procedure for Woodward EG-3P and EG-10P Actuators

SETUP

A. Connect an Ammeter in series with one of the throttle leads which are connected to the Actuator receptacle.

B. Set the Ammeter scale to 100 mA. B. There are no measurable results from this step.

C. Open the Generator Circuit Breaker. C. There are no measurable results from this step.

D. Start the engine, and bring it up to RUN. D. There are no measurable results from this

step.

TERMINAL SHAFT ADJUSTMENT

A. Disconnect the coupling from the actuator shaft (refer to Figure 2-9). Adjust the actuator so that it draws 30 to 60 mA. Monitor the Ammeter of all actuators, in RUN, Off-line, with

engine warmed up.

For each 2.5 mA of change desired, rotate the coupling on the threaded rod connected to the actuator shaft ½ to 1 turn.

Actuators and linkages must also be set to conform with the engine

manufacturer's specifications. A compromise between the engine manufacturer's specifications and the 30 to 60 mA figure may be necessary. CATERPILLAR Series 3500 engines do not conform to the 2.5 mA change per ½ to 1 turn of the coupling of the threaded rod.

A. On actuators produced beginning in 1980 Ammeter readings on all units should be within 10 mA of each other. On older units, the Ammeter readings may have to be the same for good load sharing. If you have questions, call the Ross Hill Field Service Office.

Figure 2-9. Actuator Linkage REASSEMBLY

A. Stop the engine.

B. Disconnect the Ammeter and reconnect the throttle lead.

B. There are no measurable results from this step. LOCK NUT THREADED ROD ACTUATOR ACTUATOR SHAFT

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Table 2-6. Calibration Procedure for Woodward EG-B 10P Actuators Used on EMD Engines

ACTUATOR CURRENT CHECK

A. Remove the top cover plate by unscrewing the four corner screws.

B. Connect an Ammeter, set to read 100 mA, in series with one of the throttle leads which are connected to the terminal strip located in the Engine Control Cabinet which is adjacent to the engine.

C. Open the Generator Circuit Breaker. Start the engine, and bring it up to RUN. Monitor the actuator current.

D. Compare the actuator currents of all units.

This calibration procedure is to ensure that all of the actuators will work together. In most cases, if the actuator currents of all the actuators are within 10mA between the highest and lowest reading, they will perform properly.

A. A 1/8" Allen Head adjustable Spring Seat will be visible in the middle of the actuator about 1" (2.54 cM) below the top. The seat is held tight by a 5/16" lock nut.

B. There are no measurable results from this step. C. Record the actuator current, then repeat Steps

A, B, and C for all the actuators.

D. Determine which (if any) of the actuators require adjustment. If any do require adjustment,

perform the following Terminal Shaft Adjustment procedure on the identified unit(s).

TERMINAL SHAFT ADJUSTMENT

A. Loosen the Spring Se at lock nut. Rotate th e Spring Seat 1/4 turn or less in either direction. B. Adjust the Spring Seat until the A mmeter reads

the same as other recorder actuator currents. C. Tighten the Spring Seat lock nut.

PRESSING DOWN ON THE LOCK NUT CAN CAUSE THE ENGINE TO OVER SPEED.

A. Note that the actuator current changes.

B. All actuators should draw 30 to 60 mA when th e engines ar e at RUN RPM, Off -line, and at

normal operating temperature.

C. There are no measurable results from this step.

REASSEMBLY

A. Stop the engine.

B. Disconnect the ammeter from the actuator circuit and reconnect the throttle lead.

C. Reattach the top cover plate with the four screws.

A. There are no measurable results from this step. B. There are no measurable results from this step. C. There are no measurable results from this step.

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2.3 Theor y of Operation

The Generator Unit controls the engine/generator set to deliver a constant AC supply to the Main AC Bus (refer to Figures 2-10 and Figure 2-11). Note that the AC Control Module contains the electronic Engine Governor, Voltage Regulator, Protection and Master/Slave circuits.

2.3.1 Hands-Off Circuit (HOC)

The HOC consists of a battery charging circuit connected to two 12 Volt batteries. Phases A and B of the Main AC Bus are tapped, fused, and then rectified in a diode bridge to obtain the battery charging current. The batteries supply power for the Engine Starting circuit and the Pulse Pickup circuit in the AC Control Module (refer to Figures 11 and 2-12).

2.3.2 Generator Circuit Breaker

The Generator Circuit Breaker isolates the Main AC Bus from the generator. It has a magnetic trip unit which trips the circuit breaker if current exceeds a preset value. The circuit breaker has a UV (Under Voltage) coil which is interlocked with an AC Control Module Protection circuit. This circuit trips the circuit breaker for various abnormal conditions such as reverse power, under/over-frequency and over-voltage.

2.3.3 Sy nchronization Panel

When the Main AC Bus is energized and another generator supply is to be connected to the Main AC Bus, it is essential to match their voltage and frequencies before closing the Generator Circuit Breaker. This is accomplished by comparing the two frequencies by means of the Synchronization Box (shown in Figure 2-11).

When the front panel SYNC switch is in the OFF position, the Sync panel VOLT meter

indicates the Main AC Bus voltage. The needle of the SYNCHROSCOPE and the SYNC LIGHTS compare the frequencies of the Main AC Bus and the on-coming generator. The

needle of the SYNCHROSCOPE rotates and the SYNC LIGHTS illuminate brightly when

the two frequencies are out of phase. When the frequencies and phases are identical, there is no potential across the scope and the lights. As a result, the SYNCHROSCOPE

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2.3.4 Engine Governor

The electronic Engine Governor controls the engine speed and horsepower, and thereby regulate the generator frequency (refer to Figures 2-13 and 2-14). Located in the AC

Control Module, the Engine Governor is a feedback control circuit. See the Unique Devices section of this manual for a general description of the feedback control circuit.

The governor output is connected to a Throttle Control Actuator (this controls the engine fuel line valve). The Throttle Control Actuator opens the valve in direct proportion to the current applied by the governor through its coil. The coil signal can be monitored at the AC Control Module across Pin 533 (Throttle+) and Pin 545 (Throttle-).

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ENGINE GOVERNOR (Continued)

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Figure 2-13. Engine Governor Block Diagram

RAMP CKT. M/S SWITCH THROTTLE ENGINE PULSE PICKUP SPEED REFERENCE ENGINE CONTROL SWITCH MS LOGIC MASTER/SLAVE LOGIC SLAVE SLAVE MASTER SLAVE Z8 Z9 Q4 GEN. GEN. BUS DEMODULATOR Ι REAL FEEDBACK SPEED FEEDBACK THROTTLE LIMIT AC MODULE MASTER SLAVE TO OTHER GEN. UNITS

CURRENT CONTROL LOOP

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The engine governor employs two feedback control loops. The Outer Speed Control Loop matches the actual generator frequency to the applied speed command. The Inner Current Control Loop matches the horsepower (KW) output of all engines on line.

Speed Control Loop

Op Amp Z8 issues a speed command which is proportional to the difference between the Speed Command and the Composite Speed Feedback. Speed Command is the Speed Reference signal as modified by the Engine Control switch ramp circuit and the

Master/Slave Logic signal. Composite Speed Feedback is the sum of the Speed Feedback and Throttle Limit signals.

Speed Reference

This signal is set by the operator on the front panel SPEED ADJUST knob. The SPEED ADJUST knob is linked to a potentiometer which outputs a Zero to +11 VDC signal (pin

551). This corresponds to ≈46 to 54 Hz generator frequency.

Engine Control Switch

When the ENGINE CONTROL switch is moved from IDLE to RUN, the ramp circuit

generates an ascending ramp. This steadily increases the gain of Op Amp Z8. The ramp circuit generates a descending ramp when the switch is moved from RUN to IDLE.

Changeovers in engine speed are thus accomplished smoothly over a 10 Second time span.

Master/Slave Logic

A signal from the Master/Slave Logic circuit disables the Speed Reference signal when the Generator Unit is in the Slave mode.

Speed Feedback

This signal is a low-level DC analog of the engine speed. At TP 19 in the AC Control Module, the Speed Feedback signal is -2.5 VDC at 50 Hz and ≈+5.0 VDC at 35 to 40 Hz (the IDLE frequency). The Speed Feedback signal is derived either through a Tachometer

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Pulse Pickup Circuit

A magnetic pickup device is mounted near the flywheel of the engine. The magnetic Pickup device emits a pulse each time a flywheel tooth passes by. These pulses are applied to the Pulse Pickup circuit in the AC Control Module as Tach+ (pin 526) and Tach- (pin 527). The pulse signal is processed to derive the Speed Feedback signal. The

magnetic pickup device generates it's own voltage and must produce ±2 VRMS. The Pulse Pickup also activates the HOC circuit (refer to Figure 2-12). This allows the HOC batteries to power the AC Control Module during the time that the generator voltage is building up.

Frequency Demodulator Circuit

Generator phase voltages out of AC Regulator transformer T10 are processed through a Demodulator circuit in the AC Control Module. The Demodulator output is inverted via Op Amp Z5 to obtain a negative Speed Feedback signal.

Speed Feedback Switch

The AC Control module is equipped with a circuit that permits the tachometer circuit to provide a speed feedback signal until the generator voltage is >200 VAC. When this occurs, the Speed Feedback Switch operates to connect the Frequency Demodulator Circuit output to the Frequency Regulator as the speed feedback signal.

Speed Control Loop

Op Amp Z9 issues a Throttle Current Command which is proportional to the error in signal levels between the Speed Command from Op Amp Z8 and the IREAL (KW) feedback. The output of Op Amp Z9 output is amplified through transistor Q4 and then applied to the Throttle Actuator Coil via Throttle+ (Pin 533) and Throttle- (Pin 545).

Master/Slave Logic

The Master/Slave circuit decides which current command Z9 should receive. If the

generator is a Master, the Generator Cubicle M/S switch selects the Z8 output. If, however,

the generator is a Slave, the Generator Cubicle M/S switch selects the Master/Slave signal

(pin 543). This signal is the Master generator Z8 output.

The Master/Slave Logic circuit detects whether the generator is the Master or Slave. The Master/Slave Logic circuit receives the M/S Logic signal from the Generator Circuit Breaker (pin 544) and Slave signals which are the M/S Logic signals of the other generators (pins 537 through 542). Table 2-7 is the Master/Slave Truth Table.

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Figure 2-15 shows the Master/Slave circuit. The Master/Slave Logic switches from ≈10 VDC (this voltage is approximate since it is partially dropped through a resistor) to -16 VDC when the circuit breaker is closed to connect the generator to the Main AC Bus. The

Master/Slave Logic of each generator is connected to the Slave inputs of the following higher-numbered generators. As a result, the Master generator is always the one with the lowest number. Generator 1 is never a Slave unit since it doesn't receive any Slave inputs. If Generator 1 is off, the lowest-numbered generator connected to the Main AC Bus

becomes the master.

Note that Master/Slave lines of all generators are tied together.

Table 2-7. Master/Slave Truth Table

M/S Logic Slave Result

≈10 VDC ≈10 VDC The ge nerator is disconnected from the Main AC Bus. -16 VDC ≈10 VDC The generator is

the Master. -16 VDC -16 VDC The generator is

the Slave.

IREAL Feedback

IREAL is a low-level DC analog of the real current produced by the generator (IREAL x E =

KW). Generator phase voltages out of transformer T10 and line currents out of CT1, CT2, and CT3 are processed in the AC Control Module through a current demodulator to

develop ITOTAL, I REAL and IREACTIVE signals (refer to Figure 2-10).

2.3.5 Voltage Regulator

This controls the generator's exciter current through the exciter power supply to regulate the generator voltage (refer to Figures 2-11, 2-13, 2-16, and 2-17).

The Voltage Regulator output can be monitored across Generator EX+ (TB11-7) and

Generator EX- (TB11-8). It should be +10 VDC during IDLE and ≤+70 VDC during RUN for a nominal 100 VDC exciter.

The Voltage Regulator employs two Feedback Control Loops (Inner and Outer). The Outer provides overall regulation by matching the generator voltage to the Voltage Reference. The Inner regulates the Exciter Field Supply. Op Amp Z1 issues the Exciter Current Command. It is proportional to the error difference between the Voltage Reference and Voltage Feedback signals.

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Figure 2-15. Master/Slave Wiring Diagram Voltage Reference

This is set by the operator on the front panel VOLTS ADJUST knob. The knob is linked to a

potentiometer which outputs a Zero to +11 VDC signal (Pin 551). This +11 VDC corresponds to maximum voltage.

Voltage Feedback

Voltage Feedback is a low-level DC analog of the generator voltage. The generator AC line voltages are applied to the primary of Control Transformer (600:115 VAC) T10. T10 has a Delta/Star configuration. The six AC phase voltages from the secondary are rectified and reduced in value to give the feedback signal. IREACTIVE is a low-level DC analog of the

generator reactive current (IREACTIVE x E = KVARs).

Figure 2-16. Voltage Regulator Block Diagram

MS LOGIC MASTER SLAVE SLAVE SLAVE SLAVE

PIN O. N PIN O. N PIN O. N

AC MODULE

GEN. 1 AC MODULEGEN. 2 AC MODULEGEN. 3

CB AUX. CB AUX. CB AUX.

-16 VDC -16 VDC -16 VDC 544 544 544 543 543 543 542 542 542 541 541 541 540 540 540 SCR FIRING CIRCUIT Z1 Z2 AC MTR EXCITER GEN. BUS GENERATOR EXCITER FIELD SUPPLY VOLT. REFER. UNDER FREQUENCY CUTBACK Ι AC MODULE VOLTAGE FEEDBACK EXCITER CURRENT FEEDBACK

EXCITER CURRENT CONTROL LOOP VOLTAGE CONTROL LOOP

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Figure 2-17. Exciter Field Supply Circuit

The voltage feedback and current feedback signals are processed in the AC Control Module to derive the IREACTIVE signal.

The IREACTIVE signal is negligible during startup when the circuit breaker is open since

minimal current flows out of the generator. Voltage Reference is the only effective signal. The VOLTS ADJUST knob can be adjusted to set the generator voltage to the operating

level. When several generators are connected to the Main AC Bus, the terminal voltage is held fixed by other generators. The VOLTS ADJUST knob can now be adjusted to bias the

IREACTIVE signal so as to distribute the reactive current (KVARs) equally among all

generators.

The Underfrequency Cutback Signal is developed from the frequency feedback. It applies a negative bias to the summing junction of voltage regulator Op Amp Z1 to cutback the generator voltage when frequency drops below 42 Hz. At IDLE, when the frequency is

approximately 30 to 38 Hz, the voltage is between ≈300 VAC to 450 VAC.

2.3.6 Exciter Current Control Loop

Op Amp Z2 controls the SCR firing circuit firing angle so that the exciter field current matches the Op Amp Z1 current command.

The generator output (refer to Figure 2-17) is stepped down and rectified to produce the exciter current. Two rectifier circuits are used: a diode bridge made up of DB1 and DB2 during startup. Thereafter, a half- controlled bridge made up of two diodes (DB2) and two SCRs (SCR1, SCR2). During startup, generator residual voltage is rectified through the diode bridge and applied to the Exciter. The Metal Oxide Varistor (MOV) clamps bridge voltage to +250 VDC. Through positive feedback, the Exciter voltage, and in turn, the generator voltage quickly builds up. When the voltage is sufficient to energize the AC

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Control Module, build-up relay K1 energizes to switch the transformer output to the half-controlled bridge. The Exciter current feedback to the Op Amp Z2 summing junction (IEX +

and IEX -) is +0.33 VDC per 1.0 Amp of Exciter current (or as adjusted by the connection of

current-sensing resistors).

2.3.7 Protection Circuit

This circuit (refer to Figures 2-13 and 2-18) compares the generator supply parameters against their respective preset limits.

It consists of a Protection switch controlled by the reverse power, under/over-frequency and the over-voltage detector.

The Protection switch, made up of transistor Q3 and relay K2, de-energizes the Under Voltage (UV) coil to trip the Generator Circuit Breaker. In some systems, the Generator Circuit Breaker has a Shunt Trip coil and a UV coil. In these systems, the Shunt Trip coil is wired to a switch on the Generator Cubicle. Closing this switch will energize the Shunt Trip coil, thus causing the Generator circuit breaker to trip.

Figure 2-18. Protection Circuit Block Diagram

GEN. BUS AC MODULE AC BUS AC CIRCUIT BREAKER CB TRIP NO PULSE I REAL FREQUENCY FEEDBACK VOLTAGE FEEDBACK REVERSE POWER LIGHT UNDER FREQ. CUTBACK REVERSE POWER DETECTOR Z6, Q1, K1 UNDER/OVER FREQUENCY DETECTOR Z7, Z14 OVER VOLTAGE DETECTOR Q6 PROTECTION SWITCH Q3, K2 UV

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2.3.8 Reverse Power Detector

When an engine is running normally, it supplies power to the Main AC Bus. This power is measured in terms of KWs. The front panel KW METER will display a normal positive

value (> zero). However, when fuel to the engine is cut off due to overtemperature, oil pressure or because of a clogged fuel filter, the corresponding KW meter will display a negative reading (below zero). This is because power flows from the bus into the generator of the faulty engine. The generator functions as a synchronous motor which keeps the faulty engine running.

This is termed the reverse power phenomenon. Normally-running engines will force a faulty-running engine to run at the same speed because of the magnetic coupling linking the generators by way of the Main AC Bus.

Comparator Z7 in the Protection circuit monitors the IREAL (Kilowatts) feedback signal to

trigger the Protection switch when the signal exceeds the preset limit. The time delay before tripping of the circuit breaker is a function of the level of the reverse KW. For example, if reverse power is 7%, the Circuit Breaker will trip in eight to 12 Seconds.

2.3.9 Under-Fre quency Detector

Comparator Z6 triggers the Protection switch if the frequency feedback signal indicates that the frequency is below 42 Hz. Z6 also applies the Underfrequency Cutback signal to the Voltage Regulator circuit to reduce generator voltage.

2.3.10 Over-Frequency Detector

Comparator Z14 triggers the Protection switch if frequency feedback signal says that the frequency is 56 to 57 Hz.

2.3.11 Over-Voltage Detector

The Voltage Feedback signal is applied to a voltage divider circuit made of resistors R90 and R96. The output of the voltage divider will trigger Q6 if the line voltage >≈1.16 x normal bus voltage.

2.3.12 No Pulse Detector

The No Pulse signal will switch from +16 VDC to -16 VDC when the Pulse Pickup circuit does not receive pulses from the Magnetic Pickup device (this is located near the engine flywheel).

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The Protection switch operates 100 mS after loss of magnetic pulses from the engine. This will prevent nuisance tripping of the circuit breaker.

2.4 Power Limit Circuit

The Power Limit Circuit prevents the load from exceeding the capacity of engines on line. The circuit monitors IREAL (KWs) and ITOTAL (KVAs) of all the generators to keep the SCR

bridges on line from demanding more of either KWs or KVAs that would exceed preset limits. This action distributes the available power equally among the SCR bridges. The power limit is normally set at ≈95% of the engine's horsepower rating and 100% of the generator's KVA rating.

Note that IREAL and ITOTAL signals are generated in the AC Control Module and auctioneered

together so that only the signal from the most highly loaded engine/ generator goes to the power limit circuit (see Figures 2-11, 2-14, 2-19 and 2-20)

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The IREAL and ITOTAL signals are low-level DC analog signals representing the real and total

currents developed by the generator. Generator line currents are stepped down through current transformers CT1, CT2 and CT3. The resulting low level AC signals are rectified and processed in a current demodulator in the AC Control Module with the generator phase voltages and rectified to derive IREAL and ITOTAL. The IREAL and ITOTAL signals of all

generators connected to the Main AC Bus are auctioneered to select the signals with the highest positive values. The Power Limit signal (Op Amp Z1-6) goes positive as the load increases. It is +0.25 to +0.5 VDC measured at Pin 12 of the Power Limit Board at power limit. When the load exceeds the power limit, the Power Limit signal positively biases the negative Firing Reference signals to all SCR bridges on line. Op Amp Z2 ramps input signal to Z1 from 75% of Power Limit to allow the prime mover to handle a large change demand for power. Transistor Q1 turns on at power limit to turn on the Driller's Console

POWER LIMIT light. In some systems, Op Amp Z4 output is used to drive the Driller's

Console POWER LIMIT meter.

2.5 AC Ground Fault Detection Circuit

This circuit (refer to Figure 2-11) consists of three lights. One side of each light connects to a phase of the Main AC Bus. The light's other side is grounded. If an AC phase becomes grounded, the light corresponding to that phase is extinguished. The other two lights

become more brightly illuminated. A small C.T. drives a meter to indicate the percent of the AC ground. This manual's SCR Unit section describes the DC Ground Fault Detection circuit.

2.6 TROUBLESHOOTING

Table 2-8 gives troubleshooting information for engine malfunctions. Table 2-9 gives troubleshooting information for Generator malfunctions. Table 2-10 gives troubleshooting information for the AC Control Module.

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Table 2-8. Engine Malfunctions

SYMPTOM/PROBABLE CAUSE ACTION

ENGINE WILL NOT RUN

A. Engine overspeed lever not reset. A. Reset the lever. B. No power to the a ctuator. Throttle drops shut if

the fuel rack is n ot held open by ha nd. Th e possible causes are:

B. The actions for the possible causes are: 1. Leads to the throttle actuator are either open,

short-circuited, or grounded. 1. Measure resistance between Generator TB11-1 and Generator TB11-2 (Throttle + and -) with both leads lifted. It should read 30Ω.

2. The AC Co ntrol Modul e in the Generato r Cubicle is not providing control current to the throttle.

2. Measure current going to the Throttle Actuato r at throttle + or Throttle -. It s hould be 30 to 60 mA when e ngine is at run speed. If there is n o or low current, replace the AC Control Module. 3. No signal from the e ngine pul se pickup (if

used). 3. Set the Voltmeter on it's lowest AC Volts range. The pulse pickup must deliver at least 2 VAC at engine crank speeds.

ENGINE RUNNING PROBLEMS

A. Engine speed oscillates up and down at a steady

rate. Observe the engine throttle arm. A. Speed may oscillate for a sho rt time durin g col d starts (this is normal). If it continues to oscillate, the AC Cont rol Module may be malfuncti oning. If so, call Ross Hill.

B. Engine speed vari es erratically wit hout any

steady oscillation. The possible causes are: B. The actions for the possible causes are:

1. Intermittent connection on the throttle circuit. 1. Check for/repair any intermittent connections. 2. Defective AC Control Module. 2. Replace with spare AC Control Module.

C. Engine speed cannot be raised to 50 Hz. C. The A C control voltage s from tran sformers n ot reaching the AC Control Module. Troubleshoot and repair. With the EG-B-1 0P throttle actuator, be sure SPEED knob setting is set to MAXIMUM.

D. Engine speed cannot be adjusted. D. Faulty SPEED ADJUST rheostat. Troubleshoot and

repair.

E. Engine speed and KW sharing problems. E. AC Control Module is defective. Check the actuator current.

F. Generator Circuit Breaker does not a utomatically trip for reverse power, under/overfrequency, or no pulse faults. There are two possible causes:

F. The actions for the possible causes are: 1. Defective AC Control Module. 1. Replace with spare.

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Table 2-9. Generator Malfunctions

AC VOLTS ABSENT OR <150 VAC.

A. Engine speed is too low. A. If the Main AC Bus voltage will not increa s e, raise the speed to RUN setting when starting.

Measure the voltage across Exciter Field+ (GEN TB11-7) an d Exciter Field- (GE N TB11-8 ). It must be at le ast 1 VAC d uring starting. Check the Generator Residual Voltage. At full speed, it should be ≈15 to 20 VAC.

If both of the above conditions do not exist, the Generator Residual Voltage is insufficient. In this case, supply an external current to the Generator Exciter Field (this proced ure i s call ed flashing

the Exciter Field ).

B. Exciter fuses are blown, or the Exciter Fiel d

Supply Circuit is defective. B. Troubleshoot the Exciter Field Supply Circuit. C. Shorted diode in the generator rotating rectifier. C. Troubleshoot and repair the generator. D. Generator Residual Voltage insufficient. D. Flash the Exciter Field.

AC VO LTAGE REACHES 150 TO 200 VAC BUT DOES NOT INCREASE TO 600 VAC

A. Defective Exciter Printed Circuit Card. A. Replace the Exciter Printed Circuit Card. B. Defective AC Control Module. B. Replace with spare AC Control Module.

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Table 2-10. AC Module Troubleshooting

POWER SUPPLY TRANSFORMER

A. The Generator Voltage is high. A. Check the voltage s on P ins 51 2 thro ugh 51 7 are missi ng (they sh ould each be 11 5 VAC mea sured i n refe rence to ground). Absence of any will cause this condition.

Check the S afety Fuses and Fuses F33, F3 4, a nd F 35. Replace if re quired. If the problem repeats, replace the AC Control Module.

DC POWER SUPPLY

A. The KVAR and KW meter nee dles

oscillate against their Zero Stop pin. A. Measure the voltage at t he follo wing AC Control Module Pins:

Pin Voltage

501 Zero Volts (This point is ground) 502 +16( ± 0.15) VDC

503 -16( ± 0.15) VDC 546 +11( ± 0.15) VDC

These voltages should be present whenever the Generator voltage >250 VAC. This condition can be caused by Pin 501 not being tie d to grou nd and TB4-1 0. Troubl eshoot and repair/replace as required.

B. Generator Voltage rea ches 6 00 VAC but DC Power Supply is not working correctly.

B. Measure the voltage at the following AC Control Module Pins when the Generator Voltage is 600 VAC:

Pin Voltage

502 +16( ± 0.15) VDC 503 -16( ± 0.15) VDC 507 -160( ± 20) VDC 508 +160( ± 20) VDC

If voltages are incorre ct or missin g, troubl eshoot an d repair/replace as required.

GENERATOR VOLTAGE REFERENCE

A. Unable to adjust generator voltage. A. A low re ading at Pin 55 1 of the AC Control M odule will cause this p roblem. Ensure that the VOLTS ADJUST is set

at ≈ half rotation. Measure the voltage at Pin 551, i t should read ≈+6 VDC when the Generator Output is 600 VAC. The range a djustment for the Gen erator Voltage Reference i s Zero to +11 VDC.

If the voltage at Pin 551 is missing, trouble shoot and repair/replace as required.

ENGINE SPEED REFERENCE

A. Engine speed is low a nd/or AC Ci rcuit

Breaker trips due to underfrequency. A. Absence of a signal at Pin 547 of the AC Control Module will cause this problem. Set the SPEED REFERENCE to 50 Hz

and then me asure the vol tage at Pin 547. It should be +6 VDC. The range adjustment for the Engine Speed Reference