Diesel Generator Problem

[woody]

I have a 60hz 208v generator powered by a 371 cummins diesel. When I got it the DC power wire from the solenoid to the control box was badly burned. I replaced the DC breaker and rewired the bad wire. It was built in 1969 by Condec Corporation. It runs great but I cant control the voltage. I can govern it down and control the hz and the voltage adjusts comparably. The only problem is that I cant get 60 hz and 208v at the same time. The voltage adjust reostat has no affect. It checks out with an ohms meter. Could this be a voltage regulator problem? Any help would be great thanks.....Troy

 

[mattc]

What other info do you have<br>
ie: Engine controls?<br>
AC/DC boards?<br>
Are the 12 leads acurately flagged?<br>

 

[khalid]

First of all I wowuld like to mention that the frequency is controlled by engine speed and not the voltage.The problem you explained shows that there is something wrong with generator A.V.R . Which is not regulating the voltage.If you can supply the type of A.V.R and its connection details.I hope I can tell you the method of testing.<br><br>Regards<br><br>Khalid Khan

 

[eblacker]

The frequency is controlled by engine RPM.<br>The voltage is controlled by field current.<br>You didn't mention whether the output voltage was too low or too high.<br>If it is too high then the field current is too high and if the voltage is too low the field current is too low.<br>The voltage regulator controls the field current.<br>The problem is likely to be a damaged VR.

 

[woody]

Khalid and Eblacker.... thank you for your responses.&nbsp;&nbsp;&nbsp;I still have the problem with voltage.&nbsp;&nbsp;It is too high. I have temporarily controlled the voltage with resistors but I do believe that the problem is in the voltage regulator .&nbsp;&nbsp;I will take a look when i have time to look at it again and send the connection details and type of VR.&nbsp;&nbsp;We use the generator around the shop so but I would like to be able to rent it so any help is appreciated.&nbsp;&nbsp;Thanks again ..Troy

 

[bfuchs]

Are you measuring the voltage on load ? or off load ?<br>I assume you want to ensure 208V on load, right ?<br>In this case, it is not unusual to have an off load voltage slightly higher (there is ususlly a 5% difference on transformers for instance...).<br><br>

 

[DaveK]

first off,isn't a 3-71 a GM-Detroit engine? anyway,sounds like you need a new AVR(voltage regulator)make sure your insulation is ok on the gen,get an AVR with 3phase sensing,it allows tighter voltage regulation;you probably have an old silverstat AVR,just replace it with a new modern AVR(3hot leads,1 neutral,2field leads)you'll be in business..email us for details

http://www.kuhnbros.com

 

[enginebob]

I have a question. I was told by a guy today, that a 12 wire alternator that is 3 phase, can be simply wired to single phase. Is that correct? Are most of them wired Star or Delta? And if so how would you convert to single phase? Thanks ahead of time.

 

[jbartos]

1. Most of alternators are Star-connected since the power distribution systems are supposed to have a system ground, which is better implemented over the Star-connection.
2. Assuming that you need an approximately full rated kW of the alternator, one way to implement it is over the Alternating Current (3-phase) to Direct Current to Alternating Current (1-phase) energy conversion. Another way to do it is over the connections of windings. This may need the alternator rewiring from 3-phase to 1-phase. An assessment of both approaches is needed to select the better one.
1. Reliability works in favor of 2nd
2. Cost is to be analyzed
3. Power quality works in favor of 2nd
4. If you happen to need the 3-phase power for some reason, the 1st option leaves some room for it
5. Etc.