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Personal injury or death can result from high voltage. When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present. Improper test equipment can fail and present a high voltage shock hazard to its user. Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made. When servicing or repairing electric power generation equipment:
Failure to do so could result in personal injury or death. Make sure residual voltage in the rotor, stator and the generator is discharged. |
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Accidental engine starting can cause injury or death to personnel working on the equipment. To avoid accidental engine starting, disconnect the battery cable from the negative (−) battery terminal. Completely tape all metal surfaces of the disconnected battery cable end in order to prevent contact with other metal surfaces which could activate the engine electrical system. Place a Do Not Operate tag at the Start/Stop switch location to inform personnel that the equipment is being worked on. |
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For generators with Auxiliary Winding Regulation Excitation Principle (AREP), the voltage regulator is powered by two auxiliary windings. These windings are independent from the circuit for detection of voltage. The first winding is labelled as "X1" and "X2". This winding has a voltage that is proportional with the output voltage of the generator. The second winding is labelled as "Z1" and "Z2". This winding has a voltage that is proportional to the current of the stator. The voltage from the power supply is rectified and filtered before being used by the regulator monitoring transistor. This principle ensures that regulation is not affected by interference that is generated by the load.
For generators with PMG excitation, a permanent magnet generator is added to the generator at the rear of the generator. The PMG supplies the voltage regulator with a voltage that is independent of the main generator winding. The generator has a short circuit capability of 3 X In for 10 seconds. The generator also has good immunity to distortion from the generator load.
The voltage regulator monitors the output voltage and the voltage regulator corrects the output voltage of the generator by adjusting the excitation current.
| Sustained short circuit capacity (AREP and PMG) | 3 x In for 10 seconds |
| Standard power supply (AREP) | Two auxiliary windings |
| Supply for shunt | max 150 VAC at 50/60 Hz |
| Rated overload current | 10 amperes for 10 seconds |
| Electronic protection for overload and loss of voltage sensing | Excitation ceiling current for 10 seconds and return to approximately 1 ampere THE GENERATOR MUST BE STOPPED IN ORDER TO RESET THE PROTECTION. |
| Fuse "F1" on input side | "X1" and "X2" |
| Voltage sensing | 5 VAC that is isolated by the transformer |
| Terminals for 0 and 110 VAC | 95 to 140 VAC |
| Terminals for 0 and 220 VAC | 170 to 260 VAC |
| Terminals for 0 and 380 VAC | 340 to 520 VAC |
| Voltage regulation | ±0.5% |
| Rapid response time or normal response time from the location of jumper "ST2" | |
| Voltage adjustment via potentiometer "P2" | |
| Quadrature droop adjustment via potentiometer "P1" | |
| Maximum adjustment for excitation via potentiometer "P5" (4 to 10 amperes) | |
| 50 or 60 Hz selection with jumper "ST3" (1). | |
| ( 1 ) | The engine speed setting must be changed in order to change the frequency of the generator set. |
These voltage regulators may have an optional remote potentiometer for voltage adjustment. This potentiometer is 420 ohms 3 W minimum. The adjustment range is 5%. The voltage range is limited by the internal potentiometer "P2". Remove "ST4" in order to connect the potentiometer. A 1000 ohm potentiometer can also be used to extend the adjustment range.
R448 Adjustments
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| Illustration 1 | g01144712 |
R448 Voltage Regulator | |
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| Illustration 2 | g00995942 |
Connections for shunt excitation 6 wires | |
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| Illustration 3 | g00995949 |
Connections for shunt excitation 12 wires | |
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| Illustration 4 | g00995995 |
Connections for AREP excitation | |
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| Illustration 5 | g00996011 |
Connections for PMG excitation | |
Use the following procedure to adjust the R448 voltage regulator.
Use the following procedure in order to run the generator set in parallel operation.
Adjustments for Stand-alone Generators
- Turn the remote adjustment potentiometer to the center position, if equipped.
- Connect an analog voltmeter that is calibrated for 50 VDC on terminal E+ and terminal E-.
- Connect a voltmeter that is calibrated for 300 VAC to 500 VAC or 1000 VAC to the output terminals of the generator.
- Make sure that the ST3 wire is positioned on the desired frequency. Also, the engine speed must be changed from the factory setting in order to change the frequency of the generator.
- Turn potentiometer (P2) to a full counterclockwise position.
- Turn stability potentiometer (P3) counterclockwise to about 1/3 of the total rotation for the potentiometer.
- Start the engine and set the engine speed to a frequency of 48 Hz for 50 Hz or 58 Hz for 60 Hz.
- Adjust the output voltage to the correct value with potentiometer P2. This voltage should be the rated voltage UN for single operation or UN plus 2% to 4% for parallel operation with a current transformer. Use potentiometer P3 to make adjustments if the voltage oscillates. Adjust potentiometer P3 in both directions while you observe the voltage between E+ and E-. The voltage between E+ and E- should be approximately 10 VDC. The best response times are obtained at the limit of the instability. Try cutting or replacing the wire ST2 if no stable position can be obtained.
- Check the operation of the Load Adjustment Module (LAM). ST5 must be closed. The LAM can be adjusted to 15% or 25% voltage dip by moving the ST10 jumper wire.
Adjustments for Generators in Parallel Operation
Note: Make sure that the speed droop is identical for all of the engines before adjustments are made to the generator.
- Preset the unit for parallel operation by connecting the current transformer to S1 and S2 of the connector J2. Set potentiometer P1 for quadrature droop in the center position. Apply the rated load. The voltage should drop for 2% to 3%. Switch the positions of the two incoming secondary wires of the current transformer if the voltage increases.
- The no-load voltages should be identical for all the generators that are operating in parallel. Connect the generators in parallel. Try to obtain a 0 kW power exchange by adjusting the speed of the generator. Try to minimize the circulating currents between generators by altering the voltage setting with potentiometer P2 or Rhe on one of the generators.
Note: Do not change the voltage settings after this step.
- Apply the available load. The setting is correct only if a reactive load is available. Equalize the Kilowatts or divide the rated power of the units proportionally by altering the speed. Alter the quadrature droop potentiometer (P1) in order to equalize the currents or divide the currents.
R448 Adjustment for Maximum Excitation
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| Illustration 6 | g01212297 |
The maximum factory setting corresponds to an excitation current that is required to obtain a three-phase short circuit current of 3 X IN at 50 Hz for industrial power, unless this is specified otherwise.
The maximum level of excitation may be reduced by a static method. The static method is safer for the generator and the installation. Use the following steps to reduce the maximum excitation level.
- Disconnect the power supply wires X1, X2, Z1 and Z2.
- Disconnect sensing leads 0V, 110V, 220V and 380V on the generator.
- Connect the main power supply 200V-240V to X1 and X2, as shown.
- Install a 20 Amp DC ammeter in series with the exciter field.
- Turn potentiometer P5 to a full counterclockwise position and activate the power supply. If there is no output current from the voltage regulator, turn potentiometer P2 clockwise until the ammeter indicates a stable current.
- Switch off the power supply. Switch on the power supply. Turn potentiometer P5 until the required maximum current is obtained. The maximum current must not be greater than 15 Amperes.
Use the following steps in order to check the internal protection.
- Open switch D. The excitation current should increase up to the preset maximum value and the excitation current should remain at the preset maximum value for approximately 10 seconds. The current will decrease to less than 1 Amp.
- Open switch A in order to reset the internal protection.
Note: The voltage must be adjusted after the maximum excitation current has been set.
Special Use
De-energizing the Field
| NOTICE |
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Damage will occur to the voltage regulator if the excitation current E+ and E- are left open when the generator set is operating. |
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| Illustration 7 | g00952821 |
The exciter is switched off by disconnecting the power supply to the voltage regulator. The rating of the switch contacts should be at least 16A - 250 VAC. The connection is identical for resetting the internal protection for the voltage regulator.
Forcing the Field
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| Illustration 8 | g01212159 |
Use a 12 VDC power source in order to energize the field, if necessary. Refer to the following table.
| Applications | B Volts | Time |
| Voltage build up | 6 (1A) | 1 - 2 seconds |
| De-energized parallel operation | 6 (1A) | 1 - 2 seconds |
| Standby parallel operation | 12 (2A) | 5 - 10 seconds |
| Frequency starting | 24 (4A) | 5 - 10 seconds |
| Voltage that is sustained at overload | 24 (4A) | 5 - 10 seconds |