catterpillar generator output voltage dropping. 1

[shanshea]

troubleshooting a cat generator, from start voltage output is only 280 volts phase to phase and 110 phase neutral,but after 3 mins running, output voltage drops to 40 volts all phase, and i need 380 volts. what is the problem here? is the voltage regulator 9y8400 damaged? or is it just the wiring?

generator details

catterpillar model sr4b
456kVA
365KW
3 phase
10 wires
connection wye series
generator 480V
excitation 39v
7.5 amp
voltage regulator 9Y8400

 

[waross]

280 Volts phase to phase and 110 Volts phase to neutral is not a root three ratio. Did you mean 180 Volts phase to phase?
The answer to this will influence other suggestions, but in the meantime, does the voltage change as the voltage pot on the AVR is changed (in the first three minutes).

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[henru]

vhec the wiring to regulator , diodes,and rehostat ,check the file vr3 4 connections

 

[shanshea]

@waross: thanks for the reply, you're right it's 180v phase neutral. yes the voltage is changing waross, i need a 3 phase 380v. can you give me idea how to do it? is the problem isolated only in the AVR or is there somhere else? suggestion from our head office is to jump 4+7 9+6 and 5+6 in the AVR so i can get 380 phase to phase and 220 phase neutral. i tried this but only works for 3 mins and the voltage drops to 40v.

 

[waross]

Some generic trouble-shooting suggestions.
It sounds as if the AVR may be overloading and shutting down.
I am assuming that you haven't put any load on the set yet. If you have, details please.
Monitor the voltage output from the AVR. If the AVR voltage is dropping, the next question is why.
Do you have a Permanent Magnet Generator supplying power to the AVR?
You may have a failing brushless exciter or a failing AVR.
Check the voltage and current out of the AVR. If either are too high it may trigger a shutdown of the AVR.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Some generic trouble-shooting suggestions.
It sounds as if the AVR may be overloading and shutting down.
I am assuming that you haven't put any load on the set yet. If you have, details please.
Monitor the voltage output from the AVR. If the AVR voltage is dropping, the next question is why.
Do you have a Permanent Magnet Generator supplying power to the AVR?
You may have a failing brushless exciter or a failing AVR.
Check the voltage and current out of the AVR. If either are too high it may trigger a shutdown of the AVR.
Failed diodes are another possibility. With a failed diode the AVR may go to maximum voltage trying to bring the voltage up, and trigger an over-voltage shutdown.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Motorwinder]

Take the AVR out of the circuit, and energize the exciter with a battery charger. You should get a stable voltage output.

I think you have a bad regulator.

 

[shanshea]

thanks a lot waross and motorwinder for the reply, another problem is that...this genset wadiagram for s brought here 2nd hand, and most of the terminal blocks are removed and there are lots of wire and i find it difficult to trace, can you any one give me a detailed drawing or diagram coz i'm planning to rewire it. i dowloaded the digram on the link given by henru but i can hardly read it. i think it will help a lot if both the diagram of the avr and generator will be provided.

@waross: i haven't put any load on the set.

 

[catserveng]

Try this schematic, I'm assuming an SE since mot units less than 400 ekW were not PM. If you have a PM exciter, let me know.

Bill pretty asked all the questions I would, answering them would be helpful.

On a safety note, I wouldn't use a battery charger to supply the exciter on an SR4 generator unless you are VERY familiar with what you are doing, which in your case it sounds like you're not. I use a 6 volt lantern battery, if the tail end is good it will build and hold 50-70% of rated voltage. Typical no load rated terminal voltage field volts on that machine usually about 9-14VDC at less than 1 amp.

Could be the AVR but it sounds like it trying and then going out on overexcitation. If you stop it for a while then restart and it does the same thing I'd say it is likely something else. I have seen a few VR3's fail that way but it isn't their common failure mode, they either don't work at all or go full field at start.

The 40 volts you're seeing is pretty typical for the residual level the machine will build at rated speed.

The 9Y8400 (and most VR3's) are nominal 240 sensing, and they are phase rotation sensitive. So make sure the sensing leads are hooked up per the drawing, T1=22, T2=24, T3=20, a lot of people hook them up wrong, and can cause your issues if this is an SE machine.

Mike L.

 

[Motorwinder]

The last Cat generator I worked on had this regulator. Not sure if your part number is a Cat number, but I know this will work.

http://www.dieselgeneratorsmiami.co...OY-SOMER-R448-AUTOMATIC-VOLTAGE-REGULATOR.PDF

 

[catserveng]

The 9Y8400 is a CAT VR3 voltage regulator, there were two styles, the "one fuse" and the "two fuse". If this one was shipped on the SR4B it should be a "two fuse".

The LS R448 will work to replace a VR3, especially an SE as long as the correct jumper settings are used.

The VR3 family of AVR's is no longer available from CAT, the VR6 is the normal replacement.

Mike L.