VR3 VOLTAGE REGULATOR PERMANENT MAGNET EXCITED SR4 GENERATOR Caterpillar


Testing And Adjusting

Usage:



Introduction

------ WARNING! ------

When servicing or repairing electric power generation equipment, do the following:

a. Make sure the unit is off-line (disconnected from utility and/or other generators power service), and either locked out or tagged "DO NOT OPERATE".
b. Make sure the generator engine is stopped.
c. Make sure all batteries are disconnected.
d. Make sure all capacitors are discharged.

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 being made. Improper test equipment may fail and present a high voltage shock hazard to its user.

--------WARNING!------

------ WARNING! ------

Do not connect the 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 your utility as to the applicable circumstances.

--------WARNING!------


NOTICE

At all times during operation of a permanent magnet excited generator, the VR3 voltage sensing circuit must be complete. The VR3 voltage sensing lines MUST NOT be open (broken or disconnected). The VR3 fuses MUST be installed. Operating with the voltage sensing circuit open, causes the generator output voltage to go extremely high. Damage to related equipment can occur.


Test Equipment


6V7070 Heavy Duty Digital Multimeter

Caterpillar Digital Multimeters measure voltage, resistance or current up to 10 amps. The diode function checks rectifiers. See Special Instruction SEHS7734 for the operation of 6V7070.


4C4693 Regulator Tester

The 4C4693 Regulator Tester is a bench top instrument used to test VR3 regulators. This provides a way to check a regulator without using a generator set.

Schematics - Permanent Magnet Excited Generators

Medium Voltage Generator With Two PM Fuses

Medium Voltage Generator With Three PM Fuses

4/6

Lead Generator With Two PM Fuses

4/6

Lead Generator With Three PM Fuses

10/12

Lead Generator With Two PM Fuses

10/12

Lead Generator With Three PM Fuses

SR4 Generator With Sensing/Isolation Transformer And Two PM Fuses

Troubleshooting

Introduction

Check for loose or corroded terminals. Make sure wire connections are correct. Check the accuracy of the voltmeter and frequency meter/tachometer.

To reduce troubleshooting time, simplify the system or circuit by eliminating non-essential components such as remote voltage control, manual control, etc. If, at this point, it is determined that the basic system is functioning, the circuits or components can be added back in, one at a time until the problem is located.

If elimination of non-essential components does not correct the problem, the troubleshooting procedure will check components in the basic system. If all other basic components (i.e. rotating field assembly, exciter stator, etc.) are operating correctly, then replace the VR3 regulator. As a last step after confirming correct operation under no load conditions, operate the generator under a load.

The VR3 regulator is serviced as a complete unit. The regulator fuses are the only replaceable part. VR3 regulators must be checked through the bench test before making a claim on warranty (see Bench Test).


NOTICE

Do not operate the generator with sensing leads 20, 22 and 24 disconnected or with the fuses removed. To do so will result in high unstable generator output voltage.


Problem List

Problem 1 - No AC Voltage.
Problem 2 - Low AC Voltage.
Problem 3 - High AC Voltage.
Problem 4 - Unstable AC Voltage.

Problem 1 - - No AC Voltage

Procedure A - Check AC Voltage At Regulator Between Terminals 20 And 22

* If voltage is above 200 volts for a 240V or 600V generator, or above 390 volts for a 480V generator, or above 100 volts for medium voltage generators (120 volt sensing):

Check meters.

* If 0 to 15 volts:

Go to Procedure B.

Procedure B - Check All Fuses Located On The Regulator Or In Line With PM Stator Leads 11, 12 And 13

* If fuse(s) have failed:

Look for possible short circuits that could cause fuse failure such as shorted exciter field L1, etc.

* If fuse(s) are okay:

Go to Procedure C.

Procedure C - Isolate Regulator

Disconnect leads from regulator terminals F1 and F2. Connect a 12 volt automotive type battery across exciter leads F1 (+) and F2 (-). Operate generator at half of the rated speed. Then slowly increase rpm.

* If voltage at regulator terminals 20 and 22 is 0 to 15 volts (AC), shutdown the generator and:

a. Check exciter stator L1 continuity.

b. Check rotating rectifiers CR1-6 (rotating rectifier block).

c. Check surge suppression diodes CR7-8 (varistors).

d. Check main rotor L3 continuity.

e. Check exciter rotor L2 continuity.

f. Check continuity of main stator L4 sensing wires 20, 22 and 24.

NOTE: For more information, see SR4 Generator Service Manual, Form No. SENR3985.

* If balanced AC voltage between regulator terminals 20-22-24 and not balanced between terminals 26-28-30 that increases with rpm:

Stop the engine. Disconnect wires 12 and 13 that go to the PM exciter. Check the PM exciter wires for a balanced resistance between 12-13, 11-12 and 11-13. Each resistance measured must be in the range of .2 to .75 ohms. The three resistance measurements must also be within ± 10% of each other.

* If balanced AC voltage between regulator terminals 20-22-24 and between terminals 26-28-30 that increases with rpm:

Go to Procedure D.

Procedure D - Isolate Attachments

Reconnect leads to regulator terminals F1 and F2. Disconnect all attachments such as manual voltage control, remote voltage control, droop transformer, etc.

NOTE: If remote mounted voltage adjustment is disconnected, connect jumper across terminals 4 and 7.

Check all connections to regulator and the regulator fuses.

* If generator output voltage is normal:

Check attachments.

* If voltage at regulator terminals 20 and 22 is 0 to 15 volts:

a. Replace regulator.

b. Bench test the regulator; see Bench Test.

Problem 2 - - Low AC Voltage

Procedure A - Check Engine RPM (Frequency)

Procedure B - Adjust Voltage Level With Gain Adjustment Full Counterclockwise

The voltage level adjustment range must be within +10 to -25% of rated voltage.

* If the voltage level cannot be adjusted as described:

a. Check accuracy of voltmeter.

b. Go to Procedure C.

Procedure C - Check AC Voltage Between Regulator Terminals 20 And 22

* If voltage is above 200 volts for a 240V or 600V generator, or above 390 volts for a 480V generator, or above 100 volts for medium voltage generators (120 volt sensing):

Check meters.

* If voltage is lower than 200 volts for a 240V or 600V generator, or lower than 390 volts for a 480V generator, or lower than 100 volts for medium voltage generators (120 volt sensing):

Go to Procedure D.

Procedure D - Isolate Regulator

Disconnect leads from regulator terminals F1 And F2. Connect a 12 volt automotive type battery across exciter leads F1 (+) and F2 (-). Operate generator at half of the rated speed. Then slowly increase RPM.

* If voltage at regulator terminals 20 and 22 is less than 100 volts, shutdown the generator and:

a. Check rotating rectifiers CR1-6 (rotating rectifier block).

b. Check surge suppression diodes CR7-8 (varistors).

c. Check exciter stator L1 resistance between F1 and F2 leads. Exciter stator resistance should be approximately 3 to 5 ohms.

NOTE: For more information, see SR4 Generator Service Manual, Form No. SENR3985.

* If balanced AC voltage between regulator terminals 20-22-24 and not balanced between terminals 26-28-30 that increases with rpm:

Check permanent magnet PM exciter voltage. Disconnect wires 12 and 13, that go to the PM exciter. Check the PM exciter between wires 11-12-13 for a balanced voltage increasing with speed and greater then 50 VAC at rated speed.

* If balanced AC voltage between regulator terminals 20-22-24 and between terminals 26-28-30 that increases with rpm:

Go to Procedure E.

Procedure E - Isolate Attachments

Connect exciter stator L1 leads to regulator terminals F1 and F2. Disconnect all attachments such as manual voltage control, remote voltage control, droop transformer, etc.

NOTE: If remote mounted voltage adjustment is disconnected, connect jumper across terminals 4 and 7.

Check all connections to the regulator and the regulator fuses.

* If generator output voltage is normal:

Check attachments.

* If voltage at regulator terminals 20 and 22 cannot be adjusted to rated voltage and rated frequency at no load:

a. Replace regulator.

b. Bench test the regulator; see Bench Test.

Problem 3 - - High AC Voltage

Procedure A - Check Engine RPM (Frequency)

Procedure B - Adjust Voltage Level With Gain Adjustment Full Counterclockwise

The voltage level adjustment range must be within +10 to -25% of rated voltage.

* If the voltage level cannot be adjusted as described:

a. Check accuracy of voltmeter.

b. Go to Procedure C.

Procedure C - Check Fuses Located On Regulator

* If fuse(s) have failed:

Look for possible short circuits that could cause fuse failure such as shorted exciter stator L1, etc.

* If fuse(s) are okay:

Go to Procedure D.

Procedure D - Check Connections To Regulator

* If connections are correct:

Go to Procedure E.

Procedure E - Isolate Attachments

Disconnect attachments such as manual voltage control, etc. Operate at rated rpm.

NOTE: If remote mounted voltage adjustment is disconnected, connect jumper across terminals 4 and 7.

* If generator output voltage is normal:

Check attachments.

* If voltage cannot be adjusted to rated voltage at rated frequency:

a. Replace regulator.

b. Bench test the regulator; see Bench Test.

Problem 4 - - Unstable AC Voltage

Procedure A - Check Engine RPM

* If governor operation is unstable:

a. Correct engine problem. Reference engine service manual.

b. Go to Procedure B.

Procedure B - Check for loose connections

* If connections are good:

Go to Procedure C.

Procedure C - Isolate Regulator

Disconnect leads F1 and F2 from their respective terminals on the regulator. Connect a 12 volt automotive type battery across exciter leads F1 and F2. Operate at half of rated speed and then slowly increase rpm.

* If voltage at regulator terminals 20-22 is unstable, shutdown the generator and:

a. Check connections to rotating rectifiers CR1-6 (rotating rectifier block), main field poles and other connections on the rotating (revolving) field.

b. Check connections to excitor stator L1.

c. Check permanent magnet (PM) exciter voltage. Disconnect wires 12 and 13 that go to the PM exciter. Check the PM exciter between wires 11-12-13 for a balanced voltage that increases with speed and is greater then 50VAC at rated speed.

* If stable balanced AC voltage between regulator terminals 20-22-24 that increases with rpm:

Go to Procedure D.

Procedure D - Isolate Attachments

Reconnect leads to regulator terminals F1 and F2. Disconnect all attachments such as manual voltage control, remote voltage control, droop transformer, etc.

NOTE: If remote mounted voltage adjustment is disconnected, connect jumper across terminals 4 and 7.

Check all connections to the regulator and regulator fuses.

* If generator output voltage is normal:

Check attachments.

* If voltage at regulator terminals 20-22 is unstable at rated frequency with no load:

a. Replace regulator.

b. Bench test the regulator; see Bench Test.

Bench Test

NOTE: Before making a warranty claim, use this Bench Test procedure to check VR3 regulators.

NOTE: The 4C4693 Regulator Tester with NEHS0535 Operating Manual is available for bench testing regulators. The following procedure is an alternate method of bench testing regulators.


Bench Test Circuit
(1) Voltage level rheostat. (2) Jumper - remote voltage control. (3) Voltage gain rheostat. (4) Jumper - single phase sensing. (5) 100W Light bulb. (6) AC power source. (7) On/Off switch.

1. Construct and connect the bench test circuit.

2. Install jumper (4). This sets the regulator for the required single phase sensing. Install jumper (2). Jumper (2) is always present unless a remote voltage control is attached.

3. Turn switch (7) to the OFF position. AC power source (6) must be:

60 Hz units ... 220 to 240 VAC

50 Hz units ... 180 to 200 VAC

4. Remove protective screws from rheostats (1) and (3).

5. Turn voltage level rheostat (1) and voltage gain rheostat (3) counterclockwise until the rheostat ratchets.

NOTE: Voltage level rheostat (1) and voltage gain rheostat (3) are multiple turn rheostats. The adjusting screw on the rheostat does not have a fixed stop. When the rheostat reaches the end of adjustment, a ratchet action begins. This can be felt with the adjusting tool. The adjusting screw can be turned past the rheostat stop (ratchet action) without further changing the rheostats setting.

6. Turn switch (7) to the ON position.

NOTE: If an isolation or step-down transformer is used between AC power source (6) and the regulator, it must have sufficient capacity. Measure the AC voltage between terminals 20 and 24 of the regulator. If this voltage changes more than 0.5 ACV when light (5) turns ON, a bigger transformer is required.

7. Turn voltage level rheostat (1) clockwise until light (5) first turns ON (approximately ten turns). The light should increase and decrease in intensity as rheostat (1) is turned clockwise and counterclockwise respectively. After 10 to 15 seconds at maximum intensity, light (5) should go OFF.

* If light (5) operates as described:

Regulator is okay.

NOTE: To retest the regulator, if light (5) operated as described, turn switch (7) to the OFF position for 15 seconds. If this is not done light (5) will not turn back ON.

* If light (5) reacts other than described:

Replace VR3 regulator.

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