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delta72924
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Join Date: Dec 2010
Posts: 11

Generator Voltage Drop

12/07/2010 5:37 AM

Anyone can help me on how much is the allowable voltage drop of small generator rated 230 kw, 50 hz, 400 v.

During the load test using water resistance bank @ 25 %, 50%, 75%, 100%.

at 25 % load the gen votage is 400v / 49.5 hz, @ 50% is 398v / 48.9 hz, @ 75% is 395v / 48.5 hz, @ 100% is 393 v / 48 hz. run time for each load is about 30 mins.

We ran gen for more than 1 hr @ 100 % load and the voltage drop to 385v.

The voltage drop is too high i guess. I'm clueless what went wrong. is this something to do with droop adjustment of the AVR. I dont have any idea on how to adjust this stuff. AVR has potentiometer adj for Volt, Stab, Droop.

Our generator uses mechanical governor, generatr type is 1FC2 synchronous gen , self excited, self regulating brusless machine, under licence from Siemens.

any help? thanks in advance,
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PWSlack
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#1

Re: Generator Voltage Drop

12/07/2010 10:06 AM

The reason Siemens cannot be contacted directly is what, please?

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Anonymous Poster
#2

Re: Generator Voltage Drop

12/07/2010 2:03 PM

Get the license from ABB, Cutler Hammer, Cummins.
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LAA_Lucke
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#3

Re: Generator Voltage Drop

12/08/2010 3:46 AM

1) If the generator is running single (not parallelled), then the droop adjustment should be set at Zero. The droop setting is used to match load sharing when parallelled with another generator.

2) A voltage drop of maximum 3% is quiet good: for a 400V at no load, this means a drop to 388V at full load. Therefore, 385V is still acceptable and good for a small generator with a normal precision AVR.

3) A frequency drop is more critical to watch: a drop of 1Hz means 2% and a drop of 1.5Hz is 3% of 50Hz. Your maximum drop should not be less than 48.5Hz at 100% load, if set at 50Hz - No load. This is a mechanical setting and is related to the Mechanical Governor type and precision/response ... There might be a droop setting screw on the governor. If you have such a governor, then the droop setting should be reduced to zero (if not already). This is set out of zero only if you need to parallel the genset. Check that and correct. you might improve on the frequency drop. IF NOT, then your governor is near standard and if a better frequency error is required, you need a different governor, more expensive for a tighter frequency response.
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Brave Sir Robin
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#4
In reply to #3

Re: Generator Voltage Drop

12/08/2010 9:22 AM

I agree with LAA_Lucke. Those numbers look fine.
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delta72924
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Join Date: Dec 2010
Posts: 11
#5
In reply to #3

Re: Generator Voltage Drop

03/06/2011 8:25 PM

hi, appreciate your valuable help. how can i set the correct droop setting. i have two gen in parallel with a big diffirence in current but the kw is quietly close. any thoughts about it? is this something to do with the incorrect adjutment of avr? droop? or governor? thanks again.
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kwcharlie
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#6
In reply to #5

Re: Generator Voltage Drop

03/07/2011 6:14 PM

It's the AVR, adjusting it will change the shared amps without affection the KW's much.

You need to get to the 2 threads you have started delta72924 and let us know what's going on, sounds like the same problem. Everyone would like to know if you're making good, got some GA, maybe but we don't know if you don't get back to us.

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delta72924
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Join Date: Dec 2010
Posts: 11
#7
In reply to #6

Re: Generator Voltage Drop

03/09/2011 5:45 AM

thanks for that kwcharlie, will follow ur points. appreacited much.
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delta72924
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#8

Re: Generator Voltage Drop

03/09/2011 5:52 AM

thanks for those who respond, am out of the picture for so long, sorry for the late reply. avr droop adjustment made the voltage quietly improved. it shows 3 % less
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Anonymous Poster (1); Brave Sir Robin (1); delta72924 (3); kwcharlie (1); LAA_Lucke (1); PWSlack (1)

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