DG Volt Regulator are Often Damaged

Hi

I have read your problems.Fist of all I want to sure that, you have used new DG? now This is the problems of voltage regulator only.you should use the new KAVR for voltage regulation.You should have the auxiliary winding in your DG for shunt characteristics as well as compound characteristics that will use in KAVR.Ensure that your Auxiliary winding is ok. This KVAR manages the voltage level according to increase of load. This will help you to give good voltage regulation. If DG has no auxiliary winding or it has gone bad then many company manufacturing the KAVR that will have no use of auxiliary winding ,it uses the the output voltages only.

Thanking you.

Hi Manvendra,

We have replace voltage regulator 5 times, and always replace with new part. The DG completed with auxiliry winding called permanent magnet generator to be external supply for voltage regulator to regulate voltage output throught exciter winding.

You have not given DG rating. I cannot judge overload for AVR. Often generator & AVR are capable for considerable overload with good % of rated volts. But if overload too frequent or too long duration, critical parts of AVR overheat & fail. It is a problem of cooling/heat sinking and may be improvable - you obviously have several damaged AVR to experiment with!! If you can give some information on damaged AVR I can give some suggestion. A picture of AVR would help.

Hi 67,

Apologize me, the DG is 1250 kVA and the AVR made from stamford MX321. www.cumminsgeneratortechnologies.com

Thanks. I got the MX321 AVR manual from Stamford website (limited info). Overloading probably kills the main power devices. These are connected by wide PCB tracks to terminals X and XX of AVR board. They most likely are black plastic with a metal base and 3 leads about 1 to 2 mm wide coming out of one side - there may be six of them, mounted on a metal heat-sink. If you can get the type numbers on them and tell me, that will be a good start.

It seems from MX321 description that there is a fixed time delay on field overcurrent, followed by automatic shutdown which drops generator voltage to negligible and lights lamp on AVR board. This latches ON until generator is stopped.

The size of your loads and your report of very low power factor suggest AVR has to work hard.

1. Has this field over-current shutdown operated at any time??
2. What is type number of generator??
3. Can you measure the exciter stator resistance by removing its leads temporarily from terminals X and XX of AVR ?? Ensure leads go back on same terminals!
4. Can you measure and record the exciter stator DC voltage during crane operation? Using a moving coil analog voltmeter - say every 2 seconds - to get a use profile. With 3, this would give current against time profile.
   

Hi,

Please sure that:-

1.>Is your PMG ok?

2.> Is engine rpm constant during voltage drop(during load)?

3.> Have you adjusted the doops?

You should use the kirloskar kavr.It will take only output reference for regulation.then you can able to identify the real problem.And it will meet your requirement also.It uses only output voltage for getting power and gives DC to field.You can adjust the the voltage level.It has no need the auxiliary winding to get power.It will helpful to you.

thanking you.