When servicing or repairing electric power generation equipment, do the following:
When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present. Make sure the testing equipment is designed for and correctly operated for the high voltage and current tests. Improper test equipment may fail and present a high voltage shock hazard to its user.
Do NOT connect generator to a utility electrical distribution system, unless it is isolated from the system. Electrical feedback into the distribution system can occur and could cause personal injury or death.
Open and secure the main distribution system switch or, if the connection is permanent, install a double throw transfer switch to prevent electrical feedback. Some generators are specifically approved by a utility to run in parallel with the distribution system and isolation may not be required. Always check with the utility as to the applicable circumstances.
6V-7070 Caterpillar Digital Multimeter
Caterpillar Digital Multimeters can be used to measure voltage, resistance or current up to 10 amps. Rectifiers can also be checked by using the diode function. See Special Instruction SEHS7734 for the correct operation of the 6V-7070.
8T-0900 AC/DC Clamp-On Ammeter
The 8T-0900 Digital Ammeter may be used to measure current up to 1200 amps. When measuring line current on multiple lead units, measure the current in each conductor per phase and add the currents together. See Special Instruction SEHS8420 for the correct operation of the 8T-0900.
The more common generator system malfunctions, causes of the malfunctions and appropriate repair procedures are listed in the troubleshooting chart that follows.
Incorrect electrical connections between the generator system and the regulator and poor electrical connections are often the cause of system malfunction. Before assuming a failure of the generator or regulator has occurred, check wiring against the wiring diagrams provided with the generator set and the instructions given in "Installation" section located in the Systems Operation of this manual. Also make certain all connections are tight and free of corrosion.
Before initial operation is attempted, verify that the regulator is connected for the application. (See wiring diagram provided with the generator set and review the procedures given in "Installation" section located in the Systems Operation of this manual.)
The adjustments pertaining to the voltage regulator and system operation are described in the paragraphs that follow and, except where noted, adjustment is made during initial operation and normally does not have to be repeated during the life of the voltage regulator.
Generator Voltage Adjust Rheostat (VAR)
This adjustment is provided to set the generator voltage. When set to its maximum counterclockwise position, minimum generator voltage is obtained. Maximum generator voltage is obtained when the rheostat is set to its maximum clockwise position.
Nominal Voltage Range Set Adjust (R2)
This adjustment is provided to extend the limits of the generator voltage adjust rheostat (VAR). Normally, R2 is set to provide the generator voltage adjust rheostat with an adjustment range of ± 10% from rated voltage. R2 is located on the regulator chassis. A 1/2 inch locknut must be loosened before attempting to adjust R2 with a small screwdriver. The locknut must be tightened after adjustment is complete.
Stability Adjustment (R6)
This control is located on the regulator chassis and is adjustable from the top of the regulator case. A 1/2 inch hex-head locknut that keeps the potentiometer shaft from turning due to vibration must be loosened before attempting to adjust R6 with a small screwdriver. The locknut must be tightened after adjustment is complete.
Stability control R6 provides for stable regulating operation by controlling the amount of feedback that is applied to the error detector stage. Normally it is factory set at or near its maximum clockwise position. This setting normally assures good stability, but tends to slow the response time of the generator. If rotated counterclockwise, the system response time becomes faster. However, if set too far counterclockwise, the generator voltage may oscillate (hunt). If oscillation occurs, the potentiometer should be turned clockwise past the point where oscillation stops.
The system stability is most critical at no-load. Optimum adjustment is attained when generator voltage is stable and response is satisfactory at no-load and also during operation under any load up to the full load rating of the generator. If a setting is desired that provides the fastest possible voltage response with good generator stability, an oscilloscope or some voltage recording device should be used.
Parallel Voltage Droop Potentiometer (R4)
This adjustment is provided to control the voltage droop signal of generators operating parallel. It is located on the regulator chassis. Maximum voltage droop is attained when the potentiometer is set to its maximum clockwise position. Each generator that will be operated parallel should be adjusted for identical voltage droop as described in the "Initial Parallel Operation" procedure that follows. Adjustment is made by loosening the locknut with a 1/2 inch wrench, adjusting the droop with a screwdriver and then tightening the locknut after the adjustment has been made.
NOTE: Where generator will be operating singly and use of reactive voltage droop circuitry is not desired, either set R4 to minimum droop position or install jumper or unit/parallel switch across terminals CT*bull; and CT1.
Underfrequency Adjustment (R55)
R55 is adjusted at the factory as listed in the "Specifications" section of this manual, however, if a different setting is desired, follow the procedure outlined below. Adjustment of R55 is made while the generator is running at rated speed and measuring the voltage from circuit board terminal TP1 (negative) to TP2 (positive) with an accurate dc voltmeter. The following charts lists dc voltage across TP1-TP2 for 60 Hz generators, and dc voltage across TP1-TP2 for 50 Hz generators. Adjustment is made as follows:
1. Ascertain where underfrequency limiting should begin. This is the UFL operational threshold.
2. Install accurate dc voltmeter from TP1 (negative) to TP2 (positive).
3. Run generator at rated speed.
4. Adjust R55 to position where voltage across TP1-TP2 equals the test voltage given in the appropriate table. EXAMPLE: With unit running at 60 Hz and where limiting is desired at about 55 Hz, voltage across TP1-TP2 should be -0.438 V dc. Voltage across TP1-TP2 will then drop to zero when speed is decreased to 55 Hz.
Single Unit Initial Operation Procedure
Before operating the generator for the first time, double check to make certain all wiring connections are made correctly. Review the wiring diagrams provided with the generator set, the installation instructions contained in "Installation" section located in the Systems Operation of this manual and the preceding adjustment procedures.
When the generator set is equipped with the automatic/manual voltage control option, normal operation of the generator set is the automatic voltage control mode. During generator set operation in the automatic voltage control mode, generator output voltage is pre-established during no-load operation by adjustment of the external voltage adjust rheostat and automatically maintained at the amplitude under all load conditions from no-load to full rated load by the voltage regulator.
Automatic Mode Operation
Review preceding "Adjustment" and "Single Unit Operation" procedures. General procedure for single unit automatic mode operation is as given in steps 1 through 19 that follow.
1. If the generator set is equipped with the auto-manual control option, set the selector switch to the AUTO position.
2. Turn the voltage adjust rheostat to position that is about one-half of the way between the maximum counterclockwise and maximum clockwise positions.
3. Open the output circuit breaker. Do not apply load until satisfactory no-load operation is attained.
4. If a voltage shutdown switch or field circuit breaker is used, close the switch to connect input power to the voltage regulator.
5. On generators that will be operated parallel, and if the sets are equipped with unit/parallel switches, close the switch on all generators.
6. Start the prime mover and bring up to rated speed.
NOTE: Deviation in generator output voltage approximately ± 10% of rated can be corrected by adjusting the voltage adjust rheostat and if necessary, the voltage range set adjust.
- a. Overvoltage (115% or more)
If this condition occurs, open the shutdown switch immediately and/or stop the prime mover. Determine the cause of overvoltage.
- b. Undervoltage (85% or less)
If this condition occurs, open the shutdown switch immediately and/or shut down the prime mover. Determine the cause of undervoltage.
- c. Undervoltage by Operation of the Underfrequency Limit Circuit (UFL)
Undervoltage by operation of the underfrequency circuit can occur if the prime mover governor is not adjusted to maintain rated speed or when the underfrequency limit circuit is adjusted to operate at a frequency that is very close to or greater than the rated frequency of the generator.
- d. Voltage Begins to Build Up and Collapses
If this condition exists, stop the prime mover and determine the cause of collapse. If necessary refer to troubleshooting procedure.
- e. Oscillating Voltage (Hunting)
If this condition occurs, be sure prime mover speed is not fluctuating. Then if condition persists, adjust the stability adjust (R6) as given in "Stability Adjustment."
- b. Undervoltage (85% or less)
7. Verify generator voltage. Any of the following conditions can occur.
8. Operate generator set for about one-half hour.
9. After about one-half hour of satisfactory operation, load may be applied as follows:
10. Close output circuit breaker and connect load.
11. Be sure generator output voltage is correct and stable. Verify that steady state voltage regulation is satisfactory.
12. Remove load.
13. If generator will be operating in parallel, adjust the parallel operation potentiometer R4 as given in steps 14 through 18 which follow. To stop unit, see step 19.
14. If generator set is equipped with unit/parallel switch, open the switch.
15. Monitor no-load voltage.
16. Apply inductive load and note the droop in generator voltage. A droop of about 6% is attained when R4 is turned to complete clockwise position for maximum resistance and the current transformer secondary current is one ampere connected to terminals CT* and CT1 or 5 amperes connected to terminals CT* and CT5.
17. If droop is more than is required, turn R4 counterclockwise. If droop is less than is required, turn R4 clockwise.
18. Repeat steps 15 through 17 as necessary to obtain required droop signal.
19. To stop unit, remove load, open output circuit breaker and then stop prime mover.
Due to a protective conformal coating, repairs on the printed circuit board are difficult and should not be attempted. A test procedure that may be performed to determine if the regulator is basically operational follows in the troubleshooting chart.
On generator sets equipped with the auto/manual voltage control option, operation of the generator set in the automatic voltage control mode can be compared to how well it operates in the manual voltage control mode. Faulty operation in the automatic mode and satisfactory operation in the manual mode indicates a problem in the voltage regulator while, if faulty operation in both the automatic and manual voltage control mode occurs, the problem is probably within the exciter or generator.
The regulator should be periodically inspected to ensure that air flow is not restricted. Dirt, dust, and other foreign material may be removed using low pressure (25 to 50 PSI) compressed air. Connections between the regulator and system should be checked periodically to ensure they are tight and free of corrosion.
The paragraphs that follow describe the procedures to be followed to operate two or more generators in parallel. In generating systems equipped with the automatic/manual voltage control option, parallel operation should always be made in the automatic voltage control mode. NEVER ATTEMPT TO PARALLEL GENERATORS WHEN THE MODE SWITCH IS SET TO MAN POSITION.
In order to attain satisfactory paralleling and to check for proper parallel operation all generators should be equipped with the following monitoring equipment.
- 1. ac voltmeter to measure generator output voltage (1 per set).
- 2. ac voltmeter to measure bus voltage (1 per system).
- 3. ac ammeter (1 per set).
- 4. Power factor or kVAR meter (1 per set).
- 5. kW meter (1 per set).
- 6. Exciter field current dc ammeters (1 per set).
- 7. Synchroscope or set of lights to indicate when units are in phase.
- 2. ac voltmeter to measure bus voltage (1 per system).
Checks Prior to Initial Parallel Operation
Before initial parallel operation review the procedures and checks that follow.
1. Verify that each generator is connected to the bus with the same phase rotation as that of the bus. This may be done using the same phase rotation test instrument or an induction motor of known rotation during the initial single-unit operation procedure.
2. Verify that the voltage regulating system of each generator is equipped with the parallel signal sensing transformer.
3. Make certain the parallel signal at regulator terminals CT* and CT1 or CT5 have the proper phase relationship with that of the sensing voltage at terminals E1 and E3. In applications where units are connected for reactive voltage droop, verify that the connection is made as shown in Figure 6. Cross-current compensation application requires interconnection of the system as shown in Figure 7.
4. Prior to operation, the parallel voltage droop potentiometer R4 on all regulators should be set for identical droop. This can be accomplished by individually testing each generator set, one at a time, as given in the "Single Unit Initial Operation Procedure."
Preliminary Parallel Operation
Before attempting to parallel two or more generator sets, individual sets should be tested to ensure that paralleling features function properly. The test that follows may be used.
1. On generating systems equipped with the auto/manual control option, verify that the switch is set to AUTO position.
2. Verify that the jumper bar has been removed from across regulator terminals CT* and CT1.
3. On generating systems equipped with unit/parallel switches, verify that the switch on generator set being tested is set to PAR position (open) and be sure that the switch for each remaining generator is set to UNIT position (closed). If connected for cross-current compensation, one of the connections to other generators must be opened.
4. Place the generator in operation as described in the section "Single Unit Initial Operation Procedure" through number 19. Observe procedure given in the following steps 5 and 6.
5. Apply 25% to 100% unity power factor load to the set under test. Generator voltage should change less than 1% and the frequency should decrease if the governor is set for droop operation.
6. Apply a 25% to 100% 0.8 PF inductive load. Voltage should droop. If the voltage rises instead of drooping, reverse CT leads. If droop is not correct, adjust parallel droop resistor R4 as described in the "Parallel Voltage Droop Resistor" adjustments procedure in the "Testing And Adjusting" section of this manual.
7. If wire was disconnected in step 3, reconnect it.
The instructions that follow contain the procedures in sequential order to be followed when paralleling generators. These instructions and those contained in preceding paragraphs should be completely reviewed and understood before paralleling is attempted.
1. Set auto/off/manual switch on all generators to AUTO position (generator set equipped with automatic/manual voltage control option).
2. On generating systems equipped with unit/parallel switches, set switch on unit being started (generator set No. 1) to PARALLEL position (open). Set switch on remaining generator set(s) to UNIT position (closed).
3. Start generator set No. 1.
4. Adjust generator voltage and frequency to nominal.
5. Apply the load.
6. Verify satisfactory voltage regulation and make certain frequency is not fluctuating.
7. Repeat preceding procedures 1 and 2 on generator set No. 2.
8. Start generator set No. 2.
9. Adjust generator No. 2 frequency and voltage to nominal.
10. Adjust speed of generator set No. 2 slightly higher than that of generator set No. 1.
11. Observing the synchroscope (or lights), when generator No. 2 is in phase with generator No. 1, close the circuit breaker for generator No. 2.
- a. A high ammeter reading accompanied by a large kW unbalance.
When this condition exists, the speed governor is either not adjusted correctly or is faulty.
- b. A high ammeter reading accompanied by a large kVAR unbalance.
When this condition exists, the voltage regulating system is either not adjusted correctly or is faulty.
- b. A high ammeter reading accompanied by a large kVAR unbalance.
12. Immediately after closing the circuit breaker, measure line current of generator No. 2. It should be well within the rating of the generator. Also, immediately after closing the circuit breaker, observe the kW or power factor meters. The following conditions could occur:
13. Adjust the speed of generator set No. 2 to the point where each generator is carrying the desired share of kW load. (See note following procedure 14.)
14. Adjust the voltage of generator No. 2 until the ammeter readings of both generators are near minimum. (See following note.)
NOTE: If kVAR or power factor meters are available, adjust voltage adjust rheostats for equal or proportional kVAR or power factor readings.
NOTE: To obtain best results, final adjustments should be made with full load on the bus.
15. With full load applied, readjust the speed and voltage of generator No. 2 until the desired load division is obtained.
NOTE: The best adjustment is obtained when each generator supplies the same percent of its rated current, the power factor readings are equal, or the sum of the ammeter currents is minimum.
16. In applications where three or more generators are to be operated parallel, repeat preceding procedures 7 through 15 for generator set No. 3, then No. 4, etc.
Shutting Down One or More Generators Operating Parallel
Before dropping one or more generators operating parallel from the line bus, it is essential that the total load on the bus is reduced to equal to or less than the combined capacity of the generators remaining on the bus. Shut down one or more of generator sets operating parallel as follows:
1. Reduce load to combined capacity of generators remaining on the bus.
2. Shift load to generators remaining on the bus by reducing the speed of the generator set being dropped from the bus.
3. Open circuit board and set its unit/parallel switch (on generator sets equipped with a unit/parallel switch).
4. Shutdown the prime mover.
5. In applications where three or more generators are operated parallel, repeat preceding procedures 1 through 4 for each generator set being taken off the bus.
Voltage Regulator Operational Test
Connect regulator as shown in Figure 9. Perform operational test as follows.
NOTE: This test procedure assumes the power source is 240 V ac. If 240 V ac is not available, 120 V ac may be utilized by connecting to the 120 volt tap (step 1) and utilizing a 120 volt ac power source (step 5).
1. Note the position of the internal wire (originating from terminal E3) on sensing transformer T1, for future reference. Connect it to the 240 volt tap. (See note above).
2. Connect a jumper wire between terminals CT* and CT1.
3. Set the voltage adjust rheostat (external to regulator) for maximum resistance (should be the fully counterclockwise position, if wired correctly).
4. Connect a 120 volt light bulb to terminals F+ and F-, and make the remaining connections shown in Figure 9.
Under some conditions, a light bulb can explode, releasing fragments of glass which may cause severe eye or other injury. Wear eye protection if the bulb is not enclosed in a suitable protective sheath.
5. Connect to a 240 V ac power source. (See note above). If light is on when voltage adjust rheostat is in the maximum resistance position, the regulator is probably defective.
6. Rotate the voltage adjust rheostat toward the minimum resistance position. Before reaching the minimum resistance position, the bulb should reach full brilliance. If the light does not come on at all, or is not brilliant, the regulator is probably defective.
7. Rotate the voltage adjust rheostat toward the maximum resistance position again. At the regulating point, a small change in setting of the rheostat should cause the light bulb to quickly change from full brilliance to almost fully off, and a small change in the opposite direction should return it to full brilliance. If it is necessary to change the setting of the rheostat more than about 10% of its total rotation to change the light bulb between off and full brilliance, or vice-versa, the regulator is probably defective.
8. Before re-installing the regulator in the generating system, connect the wire moved in step 1 as it was before beginning.
KCR-760 Voltage Regulator Outline Drawing
Typical KCR-760 Voltage Regulator Interconnection
Standard UFL Operational Threshold For 50/60 Hertz System
Three Phase Sensing KCR-760 Voltage Regulator
KCR-760 Voltage Regulator With UFL Or Volts Per Hertz Circuitry
Under Frequency Limit (UFL)
Parallel Voltage Droop Interconnection Diagram
Cross Current Compensation Interconnection Diagram
KCR-760 Operational Test
Effect Of Timed Gating Signal On SCR Phase Angle