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Perkins 500 KVA and 0.7 PF

Perkins 500 KVA and 0.7 PF

Perkins 500 KVA and 0.7 PF

(OP)
Hi All, this is my first post, hope I can be of help here to someone some day.

I want to run something past my brother EE's I have a Perkins 500 KVA plant at a factory that makes roof tiles (read: motors - inductive loads) I went there to see why the genset keeps shutting down.

The PF is 0.95 with the PF correction system (which is too small) and at full factory load the set is at 550 A per phase, BUT when the star delta starter is engaged for the 75kw Sullair compressor the set gets a 217 KVAr load plus the factory it goes into underspeed (1040 RPM) and stops, the PF drops below 0.7 (seen on the PF correction computer)

Am I correct in telling them that they need more PF caps? or to go to a 1 Meg plant?

This is a multi million $ plant, I am sure they can spring for another set or to get another 500 and sync them

BTW they blew up their 800KVA 11KV/400V xfmr now they have a 1 Meg Xfmr - go figure.

I calculated that they are drawing over 1140 A/ph from the mains when everything is running (including the bad PF)

TIA, Steven

RE: Perkins 500 KVA and 0.7 PF

You have a problem, but it may not be the motor starting.
Starting that motor is marginal but there may be other problems.
I would check my fuel filters and the specific gravity of the fuel against the fuel the set was tested with.
As long as the PF is above 0.8 on most gen-sets there is no problem. No PF penalties on a gen-set and the extra voltage drop from slightly greater current is often negligible.
If this is a standby rated set, it is marginal. If this is a prime power set it should start that load with no problems.
BTW, does the Automatic Voltage Regulator have Under Frequency Roll Off? And is it working properly?

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

RE: Perkins 500 KVA and 0.7 PF

(OP)
Thanks Waross

All checked already, the PF is to blame, they had the guys from the PF correction system out and the PF drops to 0.6! not enough caps on the system, they can sort that out, I have done my bit :)

Cheers mate!

RE: Perkins 500 KVA and 0.7 PF

kW loading is what loads and slows a generator. KVAR loading does not present an appreciable load to the engine and does not slow it down. With that set and that size base load and motor, you should consider that the engine may not be developing full rated horse-power.
At 1040 RPM the UFRO function of the AVR may be expected to have dropped the voltage to below 350 Volts on a 400 Volt system to drop kW demands and aid in RPM and frequency recovery.

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

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