Scr Drive System Chapter 1

SCR DRIVE SYSTEM

REVISION HISTORY PAGE SCR DRIVE SYSTEM TECHNICAL MANUAL 20605-45 Rev K 24 HOUR SERVICE (713) 467-2523

REVISION HISTORYRev. Description ERO/ECN #

A Initial Release 041251B Added Revision History page and drawing number in footer. Revised figures 1-10, 1-

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SCR DRIVE SYSTEM TECHNICAL MANUAL SCR DRIVE SYSTEM 24 HOUR SERVICE (713) 467-2523 20605-45 Rev K

SCR DRIVE SYSTEM

SYSTEM INFORMATION

DESCRIPTION

The SCR Drive System provides electrical power conversion and control for the DC motors on a drilling rig. The system regulates AC power from engine-generator sets and delivers continuously variable DC power to traction motors which are coupled to functions such as Drawworks, Rotary Table, Top Drive, Cement Pumps and Mud Pumps (see Figure 1-1).

A typical drive system consists of the following units:

• Generator Units for control of engine-generator sets.

• SCR Units for AC to DC rectification for traction motor power and control.

• Transformer Feeder Unit - AC feeder breakers to feed step-down transformers that deliver low voltage power for AC auxiliaries such as motor blowers, water pumping, lighting and living accommodations.

• DW Dynamic Brake - electrical resistance or regenerative brake for Drawworks motors.

• Field Supply Unit for DC field supply to shunt wound, separately excited DC traction motors.

• Driller's Console for control of all drilling functions from the drill floor.

• Mud Pump/Cement Pump Console for local control of the pumps during maintenance.

• Motor Control Center containing starters for AC auxiliary motors and feeder breakers for lighting panels and smaller distribution transformers.

SPECIFICATIONS

The drive system conforms to IEEE-45 standards for electrical switchgear. For offshore systems, certification can be obtained from American Bureau of Shipping (ABS), United States Coast Guard (USCG), and Det Norske Veritas. See Table 1-1 for system specifications.

Table 1-1. System Specifications

ELECTRICAL

AC Input Three phase, 60 Hz, 600 VAC Prime Power Usable KW depends on

horsepower of prime mover. Engine Governor 0.5 Hz steady-state regulation

with one Second response timeat 5% load unbalance of ratedload

Generator Voltage Regulator ±3% regulation one second

response time with ±10% loadunbalance of rated KVAR's

DC Output Zero to 750 VDC at zero through

maximum current Current Rating (Continuous Duty) SCR bridge output is usually

zero to 1,800 ADC (this can varydepending on model).

MECHANICAL

Temperature Range -22°F to 105°F (-30°C to 40°C) Cubicle Construction Fabricated from 12 gauge

cold-rolled steel with weldedconstruction and expandedmetal ventilation openings.The cubicle bus is solidcopper with a 0.0005 Inch(0.0013 cM) electroplating ofsilver.

Console Construction Fabricated from 12-gauge

#304 stainless steel platewith welded construction.

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SCR DRIVE SYSTEM SCR DRIVE SYSTEM TECHNICAL MANUAL 20605-45 Rev K 24 HOUR SERVICE (713) 467-2523

SPECIFICATIONS (CONCLUDED)

Figure 1-1. SCR Drive System

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FUNCTIONAL DESCRIPTION

Figure 1-2 shows a typical one-line diagram. Observe that power from the engine-generator sets is collected on a common AC bus.

AC to DC rectification occurs in SCR bridges. The output of the SCR bridge is applied to the DC traction motors via contactors. Contactor logic is set at the Control Console being used. Note that circuit breakers isolate each generator set and SCR Unit from the Main AC Bus.

OPERATING PROCEDURE FOR GENERATOR SYSTEM MODELS 1201 THROUGH 1650

During the following procedures, refer to Figures 1-3 through 1-6.

STARTING AN ENGINE

1. Place the ENGINE CONTROL switch to IDLE.

2. Start the engine and run it at idle speed until it is warmed up.

3. Place the ENGINE CONTROL switch to RUN.

BRINGING THE FIRST GENERATOR ON LINE

1. Turn the SYNC switch to the number of generator about to be brought on line. The PUSH TO CLOSE pushbutton on the appropriate generator cubicle door should illuminate.

2. Set the SPEED ADJUST control knob so the FREQUENCY meter indicates 60 Hz.

3. Adjust the VOLTAGE ADJUST control knob so the VOLTS meter indicates 600 Volts.

4. Charge the circuit breaker (if necessary), by pushing the CHARGE pushbutton for electrically charged circuit breakers, or by cranking the circuit breaker handle for manually charged breakers.

5. Close the circuit breaker by pushing the illuminated PUSH TO CLOSE pushbutton on the appropriate generator cubicle door.

6. Turn the SYNC switch to the OFF position.

SYNCHRONIZING GENERATORS

TO BRING AN ADDITIONAL GENERATOR ON LINE

1. (Models 1200, 1201, 1500) Turn the SYNCHRONIZING switch (Item 9 on Figure 1-3, Item 11 on Figure 1-4) to SYNC.

OR 1. (Model 1400) Turn the

SYNCRONIZING switch (Item 15 on Figure 1-5) to the number of generator about to be brought on line.

OR 1. (Model 1600) turn the

SYNCHRONIZING SWITCH (Item 20 on Figure 1-6) to AUTO.

2. Position the VOLTS ADJUST knob (Item 13 on Figure 1-3 and 1-4, Item 10 on Figure 1-5, Item 17 on Figure 1-6) so the AC VOLTMETER (Item 5 on Figures 1-3 and 1-4, Item 18 on Figure 1-5, Item 7 on Figure 1-6) indicates 600 Volts.

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Figure 1-2. Typical One Line Diagram

3. Adjust the SPEED ADJUST knob (Item 12 on Figures 1-3 and 1-4, Item 9 on Figure 1-5, Item 18 on Figure 1-6) until the SYNCROSCOPE needle (Item 20 on Figures 1-3 and 1-4, Item 17 on Figure 1-5, Item 22 on Figure 1-6)

moves clockwise (the engine/generator speed is faster than desired) and the two SYNCHRONIZING LIGHTS (Items 21 on Figure 1-3, Items 19 on Figures 1-4 and 1-5, Items 23 on Figure 1-6) brighten/dim.

2060

0-09

Rev

. A

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Item Description 1. GEN Circuit Breaker 2. AC Kilowatts Meter 3. AC Kilovars Meter 4. AC Ammeter 5. AC Voltmeter 6. Generator Run Light 7. Generator On Line Light 8. Engine Control Switch 9. Synchronizing Switch 10. Ammeter Select Switch 11. Voltmeter Select Switch 12. Speed Adjust Knob 13. Volts Adjust Knob 14. % AC Ground Ammeter 15. % DC Ground Ammeter 16. Ground Fault Indicator Lamps 17. Ground Detector Test Button 18. Power Limit Light 19. Hertz (Frequency) Meter 20. Synchroscope 21. Synchronizing Lights

Figure 1-3. Controls and Indicators for Models 1200 and 1500

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Figure 1-4. Controls and Indicators for Models 1201

Item Description 1. GEN Circuit Breaker 2. AC Kilowatts Meter 3. AC Ammeter 4. AC Kilovars Meter 5. AC Voltmeter 6. Generator Run Light 7. Generator On Line Light 8. Ammeter Select Switch 9. Voltmeter Select Switch 10. Engine Control Switch 11. Synchronizing Switch 12. Speed Adjust Knob 13. Volts Adjust Knob 14. % AC Ground Ammeter 15. % DC Ground Ammeter 16. Ground Fault Indicator Lights 17. Ground Detector Test Push Button 18. Power Limit Light 19. Synchronizing Lights 20. Synchroscope 21. Hertz (Frequency) Meter

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Figure 1-5. Controls and Indicators for Model 1400

Item Description 1. GEN Circuit Breaker 2. AC Kilowatts Meter 3. Kilovars Meter 4. AC Ammeter 5. Engine Control Run/Off/Idle Switch 6. GEN Run Light 7. GEN On Line Light 8. Push to Close Lighted Pushbutton 9. Speed Adjust Knob 10. Volts Adjust Knob 11. % AC Ground Fault 12. % DC Ground Fault 13. Ground Fault Indicator Lights 14. Ground Detector Test Push Button 15. Generator Synchronization Select Switch 16. Frequency (Hertz) Meter 17. Synchroscope 18. AC Voltmeter 19. Synchronizing Lights 20. Power Limit Light 21. Hour Meter

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Figure 1-6. Controls and Indicators for Model 1600

Item Description Item Description 1. AC Kilowatt Meter 13. Ammeter Select Switch 2. Temperature Meter 14. Engine Governor Switch 3. Kilovars Meter 15. Circuit Breaker Switch 4. AC Ammeter 16. Voltmeter Select Switch 5. % DC Ground Meter 17. Volts Adjust Knob 6. % AC Ground Meter 18. Speed Adjust Knob 7. AC Voltmeter 19. Temperature Select Switch 8. Generator Run Light 20. Synchronizing Switch 9. Circuit Breaker Push to Charge 21. Frequency (Hertz) Meter Push Button 22. Synchroscope 10. Ground Fault Indicator Lights 23. Synchronizing Lights 11. Ground Detector Test Push Button 24. GEN Circuit Breaker 12 Circuit Breaker Indicator Lights

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4. Crank the handle of the GEN CIRCUIT BREAKER (Item 1 on Figures 1-3, 1-4, and 1-5, Item 24 on Figure 1-6) once to charge the GEN CIRCUIT BREAKER.

5. Close the GEN CIRCUIT BREAKER when the needle of the SYNCROSCOPE points straight up, the SYNCHRONIZING LIGHTS go out, and the PUSH TO CLOSE pushbutton on the GEN CIRCUIT BREAKER is illuminated.

6. Position the VOLTAGE ADJUST knob so the KVAR meter gives the same reading as the other generator(s) on line.

7. Turn the SYNCHRONIZING SWITCH to the OFF position.

REMOVE GENERATOR FROM LINE AND STOP ENGINE

1. Open the circuit breaker by pushing the circuit breaker OFF pushbutton.

2. Place the ENGINE CONTROL switch in the IDLE position.

3. If the GOVERNOR CONTROL switch has an OFF position, go to the OFF position only after engine has cooled down.

4. If system equipped with a GOVERNOR CONTROL pushbutton switch, the engine must be shut down at the engine.

TURNING ON AN SCR UNIT

1. Check the Driller's Console to insure assignment for this SCR is turned off (the 12 o'clock position de-assigns all SCRs).

2. Charge the circuit breaker (if necessary), by pushing the CHARGE pushbutton (for electrically-charged circuit breakers) (refer to Figures 1-3 through 1-6) or by cranking the circuit breaker handle (for manually-charged circuit breakers). Some systems have molded-case circuit breakers. These do not require charging.

3. Close the SCR circuit breaker by pushing the PUSH TO CLOSE pushbutton (this may be mounted remotely or directly on the circuit breaker). Crank the circuit breaker handle once to close molded-case circuit breakers.

SWITCH ON AUXILIARIES

1. Close the feeder circuit breaker to feed AC supply to the distribution transformers and the MCC.

2. Close the circuit breakers corresponding to each of the blowers and auxiliaries. Set the HAND/OFF/AUTO switch to AUTO (if applicable).

3. If the motors are shunt wound, switch on the appropriate field power supplies. Each motor's field current should be ≈50 Amps (or per the motor nameplate rating).

NORMAL OPERATION

KVAR SHARING Adjust the VOLTS ADJUST knobs so all generator units KVAR meters are the same.

KW SHARING A master/slave circuit automatically balances the Kilowatts (Horsepower) among all on-line engines (the load is shared equally).

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KW SHARING (CONCLUDED)

The master generator is the lowest- numbered unit connected to the Main AC Bus. The remaining generators are slaved to the master. For example, if Generator 1, 2, and 4 are connected to the Main AC Bus, Generator 1 is the master.

In systems using Auto Share (Auto Sync) AC Control Modules, master/slave floats. No AC Control Module can be the dedicated master in an Auto Share system.

The magnetic coupling that exists between paralleled generators insures that all engine generator sets connected to the Main AC Bus at the same time will run at the same speed. The SPEED ADJUST knob on the master generator has total control of the Main AC Bus frequency. The slave units SPEED ADJUST controls are disabled.

The combination of KW (Real Power) and KVAR (Reactive Power) sharing between engine generator sets should cause all generator AMMETERS to read about the same value. Any imbalance in the readings of the various KVAR meters can be adjusted by using the VOLTAGE ADJUST knob of the generator that has the lowest KVAR meter reading.

POWER DISTRIBUTION

Distribution of the total power is governed by the following equation:

DCPower Demand = Power Used (Total - AC)

Bring additional generators on line to increase the total power available. To increase the total DC power available, increase the total power by putting more generators on line. AC power is usually a small fraction of the DC power. To increase power for a specific DC function, it also helps to reduce the power consumed by the other DC functions.

Due to the Main AC Bus feature and the Power Limit circuit, it is possible to connect as few generators to the Main AC Bus as are necessary to do the work. For economy and efficiency, match the total available power to the total load.

CRISIS OPERATION

UNIT MALFUNCTION

The GEN ON LINE and SCR ON lights will illuminate when the respective units are connected to the Main AC Bus. The lights go out when that unit is tripped off-line (disconnected from the Main AC Bus). If a generator\SCR unit becomes inoperative, continue the system operation on other units.

SYNC MALFUNCTION

If the SYNCHROSCOPE is inoperative, use the SYNC lights to parallel the generators. If both the SYNCHROSCOPE and the SYNC lights fail, use a Multimeter.

Switch the Multimeter to a 600 VAC scale. Connect it across the generator circuit breaker from the top to the bottom of any one phase. The voltage will swing from minimum to 600 VAC just as the SYNC lights should change from dim to bright. Adjust the SPEED ADJUST knob for the oncoming generator until the swing slows. Close the circuit breaker when the Multimeter voltage reading is minimum.

TRANSIENT AC SURGE

The green SURGE SUPPRESSION light will extinguish if a problem blows the Surge Suppression Circuit incoming line fuses.

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SPROCKET SLIP

The SPROCKET SLIP light illuminates when Mud Pump assignment contactors trip. This is caused by a sprocket slip, chain failure, or belt slippage on a dual motor mud pump. After the chain drive is repaired, push the SPROCKET SLIP RESET button to extinguish the SPROCKET SLIP light and to allow the contactors to close.

GROUND FAULT

The three GROUND DETECTOR lights and the % AC GROUND and % DC GROUND meters indicate ground faults.

These are only indicators and the fault must be located and

corrected.

AC ground faults can occur anywhere along the AC power network (generator to AC bus cables, feeder distribution to the AC motors, and the generator control bus in the cubicle itself). The GROUND DETECTOR lights will isolate the fault to one of the phases, and the % AC GROUND meter will indicate the degree of the fault.

DC ground faults may occur anywhere along the DC network from the DC (+) and DC (-) buses in the SCR cubicles to the motor cables. Isolate the fault to one motor by observing the % DC GROUND meter. The % DC GROUND meter needle will fluctuate as the faulty motor speed is changed.

SHUT DOWN INSTRUCTIONS

1. Turn off the SCR unit by tripping the SCR circuit breaker. The SCR ON light will extinguish.

2. Disconnect the generator from the Main AC Bus by tripping the Generator circuit breaker. The GEN ON LINE light will extinguish.

3. Push the engine IDLE pushbutton. Cool the engine per the engine manufacturer.

4. After the engine cool-down period is over, turn the Generator Control cubicle OFF/IDLE/RUN switch to OFF to stop the engine. Shut down the fuel rack if there is no OFF button.

CAPABILITIES

Figure 1-7 shows an SCR bridge Current versus Voltage response curve. Figure 1-8 shows DC series and shunt motors Speed versus Torque curves. These are for a specific brand and model motor. Other brands and models will be different.

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20600-91 Rev. A

Figure 1-7. SCR Bridge Current versus Voltage Curve

20600-92 Rev. A

Figure 1-8. Speed versus Torque Curve

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FS-201-01

Figure 1-9. Typical SCR House

MAINTENANCE

This chapter contains information to assure proper operation of the system through periodic functional tests and preventive maintenance.

If the system fails to perform as indicated in the functional test instructions, consult the troubleshooting guidelines listed in this manual.

RECEIVING & HANDLING

SCR switchgear is normally installed in a truckload-sized house (see Figure 1-9), a self-contained, structural steel building mounted on skids. Cabling to external devices such as generators, motors and control consoles is terminated at weatherproof plug panels (see Figure 1-10).

If the house is not ordered, the equipment should be handled with care to prevent excessive mechanical shock, and protected from possible damage due to moisture and dirt during rig-up. See Figures 1-11 and 1-12 for cubicle lifting procedure.

FS-050-11

Figure 1-10. Plug Panel of One SCR House

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Figure 1-11. Cubicle Lifting Procedure

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Figure 1-12. Cubicle Lifting Procedure

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INSTALLATION

See Figure 1-13 for a typical SCR switchgear layout in a house.

If an SCR house was not ordered, refer to the following instructions for installation of the SCR Cubicles. Figure 1-14 shows a typical SCR Drive Cubicle lineup.

Figure 1-13. SCR House Layout

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Figure 1-14. SCR Drive System Typical Cubicle Lineup

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CUBICLES

PRELIMINARY CONSIDERATIONS

Door Clearance

The SCR room must be large enough to allow the doors to be opened 90 degrees. The doors cover the full height of the cubicles. The height of the room must have clearance for the cable tray, piping, and ducting.

Ventilation and Ducting

The room air must be changed twice per minute when the cubicles are enclosed in a room. Ducting in the front and rear of the room should force the air to flow the full length of room.

Heat Loss

Heat loss for a SCR system housed in a room fully insulated on walls, floor and ceiling, and containing no distribution transformers, is approximately 2.5 tons for each 1,000 HP of DC load.

Vibration Pads

If the cubicles are mounted in a high vibration area, such as the region close to the engine skid, the cubicles should be mounted on vibration insulating pads. The vibration frequency should be within 30 Hz, and the amplitude should not exceed 0.02 cM. Korfund spring-type vibration isolators are recommended.

Location

Lift the cubicle with a crane into the general installation area. Use four lifting points per cubicle. Refer to Figures 1-11 and 1-12 for the lifting procedure.

Use hydraulic hand trolleys (Rol-A-Lift or equivalent) to move the cubicles into the exact location. Two trolleys may be required for wide cubicles such as the Motor Control Center. Cover the vertical rest beams of the trolleys with carpeting to protect the finish of the cubicle panels.

Slide the trolley horizontal forks all the way underneath the cubicle.

Jack up the cubicle approximately 6" (15 cm) above the floor.

Push the cubicle carefully into the location, jack down, and remove the trolley horizontal forks.

Mounting

Butt the sides of the cubicles tightly together.

Bolt the cubicles together at the top and bottom using 3/8" bolts.

Install the AC bus splices to connect the bus together from cubicle to cubicle.

Cable Installation

Refer to the cabling diagrams in the SCR job book. Cables between the cubicles are furnished by the customer unless the SCR drive system is installed in a Power Control Building.

All power terminations are made through the cubicle top unless otherwise designed.

If the SCR system is supplied inside a Power Control Building, power and control cable terminations are at one end of the building.

The terminations are copper stubs with an one inch diameter bolt hole. The customer should furnish plated-copper, crimp-type lugs. Avoid screw-type pressure connectors.

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If multiple single conductor cables are used to feed the system, transposing of the cables must be considered to ensure current sharing between conductors.

Control Consoles

The Driller's Console is typically mounted on top of the Drawworks pneumatic control console. The Mud Pump and Cement Pump consoles are provided with tabs. Each tab has a bolt hole for wall installation. Refer to the respective console drawings for detailed installation instructions.

Control cable terminations are made from the bottom with plug-in-type Pyle National connectors or screw-type terminal blocks fed through stuffing tubes.

TESTING

This section contains information to test the proper functioning of the SCR Drive System. Perform the test daily. If the system fails any part of the test, use the Troubleshooting section to locate the malfunction.

SAFETY PRECAUTIONS

IF CARELESSLY HANDLED, THE SCR DRIVE SYSTEM CAN INFLICT GRAVE INJURY. SAFETY PRECAUTIONS MUST

BE OBSERVED AT ALL TIMES TO PREVENT ELECTRIC SHOCK.

Team Work

Maintenance work should preferably be performed by a team of two electricians. This assures help in an emergency situation.

Personal Wear

Do not wear metallic watch straps, rings, or bracelets.

Live Circuit

Consider all circuits to be energized unless known to be dead.

Tools

All electric tools should be grounded. Handles on the tools should be insulated. Do not leave tools in the cubicles after the work is completed.

Fuses

Close a fuse by pushing on the plastic cover. Do not place a finger underneath the cover.

Fire

Remove power to the unit under fire. Read the label on the fire extinguisher to be sure it can put out an electrical fire. Water may be used, but be very certain that all power is removed including the power on the main bus.

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DAILY TEST

Perform the following checks to assure the proper functioning of the drive system.

1. Check lights and meters on cubicles and control consoles.

2. Check Ground Detector indicators. All three lamps should glow a dim orange. The Ground Fault Percentage meters should read close to Zero.

3. Check field current supply of all shunt motors.

4. Ensure that KW's and KVAR's are shared between all the generators on line.

5. During tripping, listen for switching action of the DW Dynamic Brake contactor.

6. Ensure that all SCR blowers are running.

MONTHLY TEST

Perform the "Mechanical Overspeed Trip" and "Reverse Power Trip" Functional tests, located in Table 2-4 (see Section 2).

1. Check waveshape of SCR Amps at the test pins on the DC Control Module. See the SCR Unit section for further details.

2. Inspect the cooling inlet filters and clean/replace as necessary.

When working in conditions of low humidity, wipe off meter lenses

with a damp cloth or use anti-static spray.

SERVICING

Servicing consists of cleaning the system components and replacing those which have become defective or worn out. Periodic servicing will make the SCR Drive

System more reliable and last longer. A reliable system is less likely to suffer sudden failures or deteriorate below the performance specifications.

The system components are vulnerable to three factors: inferior quality, harsh operation and severe environment.

QUALITY

Efforts to eliminate this source of failure are made at our manufacturing and testing facility. The system is rigorously tested through every phase of operation. The electronic modules are placed in ovens at 165°F (75°C) for 96 hours to simulate numerous hours of operation at normal temperature. Thus, components which are likely to fail during the first hours of operation are replaced before shipment.

HARSH OPERATION

The drive system should be operated within its capabilities. Operation above the ratings subjects the system to severe strains. The controls should be handled with care. A harsh switching action can generate a damaging transient overload.

ENVIRONMENT

HEAT

Components can fail suddenly due to overheating. Even though the drive system is rated between -22°F (-30°C) through 104°F (40°C), the system operation is more reliable at normal temperatures. Components age faster at temperature extremes.

The blowers in each SCR cubicle remove the heat from the electrical assemblies. As a further precaution, vital units such as the SCR bridges and electronic modules have heat sinks for faster cooling. Inspect the

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assemblies frequently for indications of overheating such as charring or burned insulation due to loose connections. Replace the damaged components even thought they may not have failed completely.

VIBRATION

The drive system units do not generate vibrations. However, vibrations from rotating machinery such as the generator set cause mechanical stress which can loosen connections and crack insulation.

DUST

Dust is attracted to high voltage switchgear surfaces because of the static electricity charge. As a result, circuit discontinuities, or even shorts can occur.

MOISTURE

Moisture aggravates problems caused by dust. The contaminants cake on the components and conductivity is increased. Further, corrosion can occur.

Servicing consists of three operations: cleaning, inspection, and replacement.

CLEANING

Wipe clean the cubicle and component surfaces with a lint-free cloth moistened with a mild cleaning solvent. Be sure to leave the surfaces dry.

TURN OFF THE MAIN POWER TO THE SYSTEM BEFORE CLEANING. TEST THE CLEANING SOLVENT ON A

SMALL SURFACE TO MAKE SURE IT DOES NOT DAMAGE THE PLASTIC PARTS OR INSULATION, OR REMOVE PAINT.

INSPECTION

Check all components for overheating and corrosion. Replace damaged components even if not completely failed. Inspect cables and wires for broken or burned insulation. Tighten all connections and check switches, knobs, and buttons for easy movement.

CARELESS INSPECTION ITSELF CAN CAUSE MALFUNCTIONS. DO NOT TUG CABLES AND WIRE

HARNESSES, SHAKE THE ELECTRONIC ASSEMBLIES OR FIDDLE WITH THE KNOBS. EMPLOY VISUAL INSPECTION AS FAR AS POSSIBLE.

Operating conditions dictate the servicing period. Adhere to the following schedule during the initial period and adjust it according to need.

CONNECTIONS

Experience has shown that many problems with electrical equipment are the result of loose connections. Periodic checks for tightness can be helpful.

WEEKLY SERVICING

1. Clean all cubicle and air conditioning filters.

2. Check Driller's console and Foot Throttle for air pressure. If there is moisture inside the compartments, the dryer in the air line may be clogged.

3. Check assignment contactors. Inspect the coils for signs of overheating such as discoloration or charred insulation. Check contacts for corrosion or pitting. Inspect the freewheeling diodes; also inspect auctioneering diodes in the system.

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ENVIRONMENT (CONCLUDED)

4. Clean tachometer pickup plugs. Do not screw pick up in too far. Flywheel will damage coil upon starting diesel.

5. Check AC leakage for every SCR bridge.

QUARTERLY SERVICING

Clean and inspect the system components as indicated in Weekly Servicing. In addition, tighten the bus bar bolts.

STORING AN SCR DRIVE SYSTEM

1. Disconnect HOC batteries at the battery terminals.

2. It is important to keep the SCR house interior dry while stacked. Install covers on all external connectors on the plug panels. Place corrosion inhibitors in consoles and cabinets.

3. Seal any openings to keep varmints out.

4. Lift the brushes on traction motors. 5. Apply power to generator and

traction motor heaters if possible. Heaters in electrical equipment areas are helpful.

6. Cover traction motor blower openings.

REMOVING AN SCR DRIVE FROM STORAGE AND PLACING IT IN SERVICE

1. Inspect bus bars for debris. Inspect and clean throughout cubicles, consoles, MCC cans and underneath the main and switchgear line-ups.

2. Physically rotate the SCR blowers. 3. Manually operate all motor starters

and contactors before powering up. 4. Open and inspect all modules.

5. Open and inspect all generator and traction motor covers.

6. Open all fuses in the system and high-resistance check the main three phase bus bars before applying power.

7. Remove covers and inspect SCR bridges. Clean as necessary.

8. Reconnect HOC batteries. If good, they will fully recharge within 24 hours.

9. Clean all potentiometer windings (speed adjust, voltage adjust, hand throttles, foot throttle).

10. Tighten all bus bar bolts and screw connections.

11. Manually phase-up each SCR bridge as soon as possible.

12. Inspect all power resisters for cracks. 13. Check AC leakage on all SCR

bridges. 14. Check knob settings on EGB-10P or

13P actuators. 15. Check resistance of all magnetic

pickup circuits and all actuator circuits.

16. Check compatibility of all modules. 17. Check outputs of hand and foot

throttles. 18. Check current and voltage feedback

for all SCR bridges. 19. Perform emergency-off and reverse

power trip tests for all engines. 20. Verify sync circuits with a VOM. 21. If equipment has been idle for more

than one year, all electrolytic capacitors should be replaced.

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DCELECTRONIC

MODULE

GENERATOR

CIRCUITBREAKER

DRILLER'SCONSOLE

GATE FIRINGPULSES

AC SUPPLY

POWERCONTROL

0 - 750 VDC SUPPLY

SCR BRIDGE

TROUBLESHOOTING

OVERVIEW

Troubleshooting allows the isolation of a malfunctioning SCR Drive System unit.

It consists of first looking at the broad possibilities of failure, and then breaking down the likely possibility into successively smaller trouble spots.

Examine the whole system as it is situated between the generators and the loads. Then narrow the search to a cubicle or console, then to an internal assembly, and finally to a component. The malfunction can be quickly located by seeking out signs of trouble, such as extreme readings on the meters, tripped circuit breakers, and smoking components.

A step-by-step troubleshooting approach should consist of the following items: malfunction analysis, analysis of front panel indicators, systems analysis, and signal tracing.

MALFUNCTION ANALYSIS

Troubleshooting is easier and faster if the nature of the malfunction is pinned down. Sometimes, the faulty behavior of the system may be caused by operator error. For example, the Driller may forget to turn on the lockout switch, open the throttle, and assume that the SCR unit is defective.

The faulty behavior of a motor or generator may be blamed on the SCR system. Make sure the fault is not outside the system before making extensive repairs such as replacing a SCR cell.

If the malfunction occurs off and on, it may be useful to keep a log of the system parameters with a strip chart recorder.

ANALYSIS OF FRONT PANEL INDICATORS

Many malfunctions can be located by analyzing the meters and lights on the front panel.

Warning lights on the cubicle panels flag ground faults, AC surge, sprocket slip, and reverse power conditions. Operational lights indicate whether a SCR or a Generator is on the bus. Even voltmeters and ammeters provide valuable troubleshooting information. For example, a stalled motor is indicated by high current, and low voltage. Low current and high voltage is an indication of an unloaded motor.

SYSTEMS ANALYSIS

Think of the system as being made up of interrelated blocks or units. Ignore the contents of the unit, and simply consider the inputs and outputs. Refer to Figure 1-15.

20601-07 Rev. A

Figure 1-15. System Block Diagram

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GENERATOR 1 CIRCUITBREAKER

SCR 1 CONTACTOR

GENERATOR 2 CIRCUITBREAKER

SCR 2 CONTACTOR MOTOR

SYSTEMS ANALYSIS (CONCLUDED)

A malfunctioning unit does not provide the correct outputs. The fault may be due to incorrect inputs. If not, some of the assemblies within the unit may be defective.

To troubleshoot, the system, first isolate the faulty unit by examining the outputs of the suspected units. Then examine the inputs to the faulty unit. If one of the inputs is incorrect, trace the signal from the incorrect input to its source unit. If, however, the inputs are correct and the outputs are incorrect, troubleshoot the defective unit. Isolate the fault to any one of the unit assemblies by a similar system analysis.

Inputs to many of the SCR Drive System units are of two forms: power and control. For example, a SCR cell must receive the AC supply and the control firing pulse at the gate. If both the inputs to the SCR cell are correct and the output of the SCR cell is incorrect, the cell is defective.

The defective unit can be easily located by tracing signals associated with the malfunction.

20601-08 Rev. A

Figure 1-16. A Parallel Circuit

The motor can be operated on any one of the two power lines (refer to Figure 1-16). If it fails to run, the fault can be in the motor, the assignment switch, or the power lines.

The power line can be checked out by simply switching the motor to one of the other lines. If the motor runs, then obviously, the first power line is defective.

Each power line is made up of components in series. If the power line circuit is defective, all the components and the wiring must be suspected. The defective component can be located by tracing the power supply from the motor back to the generator.

Begin the signal tracing at the motor. If power is present at the motor and the motor is not running, the motor is defective.

If power is absent at the motor, check for its presence on both sides of the contactor. If power exists on the SCR side, but not on the motor side, the contactor is open.

Signal tracing should continue back toward the Generator until the defective component is located. In extremely long series circuits, it may be convenient to divide the circuit in half. Begin the probe in the middle. If the signal is missing, trace back toward the generator until the signal is regained. If the signal is present, trace away from the generator until the signal is lost.

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SPECIAL TOOLS AND EQUIPMENT

The following instruments are needed to troubleshoot the SCR Drive System.

MULTIMETER

The Simpson Model 250 (or equivalent) is recommended to measure voltage and resistance values. The meter should be insulated, rugged and possess:

DC/AC Volts: Zero through 1,000 Volts in several ranges.

Accuracy: 3% of full scale. Ohms: Zero through 10 MΩ in

several ranges. Accuracy: 2% of arc length.

It is recommended that digital-type meters not be used for

measurements in power circuits. It has been found that, in some cases, reading inaccuracies may be induced by digital-type meter usage.

Digital multimeters may be used to measure voltage and current signals in the SCR drive but you should be aware that some digital meters are overly sensitive to the high electrical noise typical of that found in any switching high power supply. Digital meters that are not designed with proper filtering and measuring techniques and can give inaccurate readings.

AC/DC CLAMP-ON AMMETER

This meter is used to safely measure high currents. The Columbia Model 1000A is recommended.

OSCILLOSCOPE

The oscilloscope is used to check the SCR gate pulses and ripple on various DC voltages. The Tektronix Model 305 (or equivalent) is recommended. The unit chosen should have >3 Inch diagonal viewing screen and two channels for comparing two signals.

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REMOVAL & REPAIR

CUBICLE REMOVAL

If a cubicle is damaged beyond repair, perform the following steps:

1. Disconnect power cables from the bus stubs located at the top of the cubicle.

2. Remove bus links which connect the AC bus from cubicle to cubicle.

3. Remove the bolts which join the cubicles at the top and bottom.

4. Slide the fork of a hydraulic hand trolley underneath the cubicle and jack it up approximately 6" above the floor.

5. Pull out the cubicle carefully, taking care not to bump the adjoining cubicles.

CUBICLE REPAIR

Repair of the SCR Drive System normally consists of repairing an assembly within a system unit. A system unit is not replaced unless it is damaged beyond repair. When a unit is replaced, perform a functional test on it before operating the system. Refer to the respective unit manual for test instructions.

AC CONTROL MODULE

If an AC Control Module is malfunctioning, replace it with the spare AC Control Module and return the faulty unit to us.

To remove and replace the AC Control Module perform the following steps.

FS-047-02

1. Unscrew the Deutsch fastener at the top of the module and swing open the cover.

FS-047-05

2. Release the wiring harness by removing each wire from the terminal board.

FS-066-03

3. Unscrew the four Deutsch fasteners which hold the module to the cubicle wall.

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CUBICLE REPAIR (CONCLUDED)

FS-066-05

4. During new module installation, ensure you match the wire number to pin number.

FS-066-03

5. Reconnect the module to the cubicle wall with the four Deutsch fasteners.

FS-047-05

6. Reconnect the wiring harness by replacing each wire on the terminal board. Ensure that each wire is correctly placed and that the retaining screw is tightened.

FS-047-02

7. Swing the cover closed and fasten it in place with the Deutsch fastener on top.

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Scr Drive System Chapter 1