shaft generator
shaft generator
(OP)
Hi guys, need some help. i got generator rated 315 kw, 400 v, 50 hz. is it normal that when the load is on max, the voltage is seesawing from 380-460 volts. I noticed the KW & ampere meter is fluctuating which i think normal, the frq is almost constant. I wonder why the voltage palying too much , it is only happen when the load is at max, 1st step to 5th step, when the motor runs at step 1 to 4, no voltage varrying, but when we put on the max step which is 5th, the voltage is seesawing. I suspect AVR sensitivity adjustment. thanks in advance.





RE: shaft generator
What do you mean "...I noticed the KW & ampere meter is fluctuating which i think normal..."? How big are the fluctuations - are they caused by the load? What is the motor rating?
What type of AVR are you using, also do you have a PMG exciter or fed from the main terminals?
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If we learn from our mistakes I'm getting a great education!
RE: shaft generator
thanks again.
RE: shaft generator
How big is the load step from '4' to '5'? I suspect this is probably quite a big step in terms of motor power, maybe as big as 40% to 100% rating and that is what is causing part of the problem. Is the fluctuation a transient which occurs only when you change power or is it a continuous oscillation when at full power?
What adjustments are available on the AVR?
Does the AVR have a quadrature current compensation CT fitted?
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If we learn from our mistakes I'm getting a great education!
RE: shaft generator
How is the motor controlled?
Is this a DC motor?
I usually have AVR stability problems at light or no load, but by all means turn the sensitivity adjustment a little. Quick and easy.
I saw a technician from the shallow end of the gene pool completely dismantle a small alternator and prepare to oven dry the rotor and the stator. I chased him away, reassembled the generator, started it up and gave the stability adjustment a quarter turn. End of problems. I hope that I never again have to go through so much work to adjust the stability of a set.
The point is, check the easy things first.
Bill
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"Why not the best?"
Jimmy Carter
RE: shaft generator
hope this explain clear.
RE: shaft generator
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: shaft generator
What's the current limit set to on the soft start? You may find a limiter on the genny is interacting with the soft start creating a load / unload cycle. Back off the current limit on the soft start as far as you dare and see if it eases the problem.
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If we learn from our mistakes I'm getting a great education!
RE: shaft generator
thanks again scotty.
RE: shaft generator
At full load a soft start should be full on and be producing very little distortion.
At full load on a VFD the part cycle conduction characteristics of the rectifier diodes will be wreaking maximum havoc with the AVR.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: shaft generator
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If we learn from our mistakes I'm getting a great education!
RE: shaft generator
this means to say, that the installation is matched enough.
RE: shaft generator
Swap the AVR's and see whether the problem goes with the AVR or stays with the generator.
RE: shaft generator
Bill
--------------------
"Why not the best?"
Jimmy Carter