High Excitation Voltage - marine generator

[sharkboat]

Howdy -

I am having a problem with my generator Stamford/Newage in a marine application (73 ft shark research vessel)- I do everything by a shoestring and could really use some insight.

Ginny was running fine and suddenly lost power. I assumed AVR and replaced.

Come to find out the Voltage is collapsing after initial start up, lighting led on avr, with the fault being followed back to high excitation voltage (ufro and motor speed are within parameters).

I am getting 140 vdc instead of 70 vdc thru stator leads and nearly double normal voltage across terminal lugs. 3 phase - 110 - is intended output for normal operations.

Nothing I can find in any manuals is directing me on how to fix that specific problem. Anyone have some insight here? Your help would be greatly appreciated.

Thanks

Capt Chris Wade
R/V Sea Watch

 

[waross]

Check the specs on the AVR. You may have a 240 Volt AVR instead of a 120 Volt AVR.
It is always a good idea to inspect the rotating diodes and surge suppressor when changing a failed AVR.
If in doubt replace the surge suppressor.
Check also the voltage to the power terminals and sense terminals o the AVR. These terminals may be common on economy AVRs.
How is your speed/frequency?
What size set?
PMG option?
Brushless exciter?
Star or delta?
Note; Three phase 110 Volts is an unusual voltage. The last and only time I have seen it was back in '83 on an old military surplus set. 110 Volt delta at about 1 or 2 KW.
Do you actually have 120/208 Volts? That is the closest standard, but not the only one.

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

 

[sharkboat]

Thanks Bill.

AVR is a standard - Stamford MX341- replacement is exactly the same with the bridges in the correct spot. I did note that a shorting bridge was connected across terminals 1 & 2 was suggest unless a hand trimmer is used but the old avr had wires going to the leads so- I reinstalled them as was before and pulled that shorting bridge.

Sorry sir. You are correct. It is 208/120 3 P - 110 volt was me thinking ahead while typing. Not so great at the typing stuff some days.

Engine speed is correct at specific 1800 rpm.

I measured ohm between the stator leads and that was in line with specs - I want to say 19 ohms.

Yes sir - PMG genertor I believe that is is a brushless exciter - Newage WUXI is make and model.

When I was troubleshooting by flashing the battery to stator leads I could not get my htz meter reading properly. So I can not confirm htz reading right now but I am getting ready to head into engine room later today :/

Really appreciate the help and insight.

Capt Chris

 

[waross]

I hope you disconnected the AVR when flashing. I first swap the leads and the set will often come up without needing to flash. I have successfully flashed with a 1.5 Volt D cell.
A pmg is a permanent magnet generator option. It is typically added on the outboard end of the generator shaft. It supplies about 220 Volt three phase power to the AVR.
Just stepped out to do some research. Yes the MX341 is a PMG AVR.
Here is the manual for the AVR that you probably have already.

https://www.cumminsgeneratortechnologies.com/

http://www/en/common/pdfs/avr/TD_MX 341.GB_05.03_02.pdf

I would disconnect the remote voltage trim leads and put the link back. That may be the trouble.
Some Hz meters don't work unless the supply voltage is close to normal.

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