⁸What causes under voltage error in MEP-805B? Sometimes it runs fine, but ultimately will show this errer and stop generating. Seems to heal itsel

[DieselAddict]

I have a Fluke 87 meter that I bought back in the 80s when I was an electrician. It still works and I've verified its accurate with the Fluke 787. I've had to put 2 displays in it because they wash out over time but it is still kicking!

 

[SteveTheGreen]

I would refrain from paralleling until you get this fixed. Can you describe what your 3 phase load is? Load shouldn’t be all between one phase and neutral.

NDT is asking you what your load is, and not what the voltage is. What are you using for a load? Is it a three phase load? what have you hooked up, and HOW is it hooked up?

Three phase load. A is 208, B is 105, C is 105. It varies. Sometimes B and C are 195ish. And sometimes when I start it, they are all 208. It's random.

 

[SteveTheGreen]

What experience do you have with power systems? I'm concerned that your response to my question suggests you are just getting started. Poking around in live circuits is certainly hazardous. You may want to reach out to someone experienced in the hands on stuff that can help you get started in the troubleshooting.

One thing to remember when doing troubleshooting is to not assume the gauges on the machine are reading correctly. Everything needs to be verified with known good measurement tools.

I have mechanical experience, but limited electrical.

 

[SteveTheGreen]

The B phase is 16 volts under the A phase. And down to 201 volts which is too low for a 208 circuit. Is your entire 20 kW load hanging on the B phase?

Not sure what you mean. It's 30kw and when I get the undervoltage error, the generator runs, but does not produce electricity. Like someone opened the circuit.

 

[nextalcupfan]

Not sure what you mean. It's 30kw and when I get the undervoltage error, the generator runs, but does not produce electricity. Like someone opened the circuit.

What they are asking is what exactly you are powering. House, Ranch, Grocery store, etc.

And what they want to know is what your amp draw is on each leg of the generator.

On a 3 phase generator you want that to be as even as possible. If one phase is demanding ALOT more amps than the other legs it could cause the voltage to drop until the undervoltage safety kicks in.

"when I get the undervoltage error, the generator runs, but does not produce electricity. Like someone opened the circuit."
That's because that's exactly what happens.
When any error occurs the set opens the main AC contactor, cutting all power generated by the set.
(Actually now that I think about it I'm not 100% sure that's actually what happens, might need someone else to pitch in here)

 

[SteveTheGreen]

What they are asking is what exactly you are powering. House, Ranch, Grocery store, etc.

And what they want to know is what your amp draw is on each leg of the generator.

On a 3 phase generator you want that to be as even as possible. If one phase is demanding ALOT more amps than the other legs it could cause the voltage to drop until the undervoltage safety kicks in.

"when I get the undervoltage error, the generator runs, but does not produce electricity. Like someone opened the circuit."
That's because that's exactly what happens.
When any error occurs the set opens the main AC contactor, cutting all power generated by the set.
(Actually now that I think about it I'm not 100% sure that's actually what happens, might need someone else to pitch in here)

I'm powering my shop which draws between 18kw and 30kw.
I have three generators. One is running fine. This one is the only that has the low voltage error. The three are in parallel and connected with the army cables. We have looked at the power draw and they were similar last we checked. But I have not put a meter on it.

 

[nextalcupfan]

No problem "goes away". You need to read the TM if you do not know where and how to check voltage on the three phases. Go back to post #5 and start there.

I was just looking through the TM section of the forum and in your post "All the TM's you need to work on the MEP-805B Generator set"
"TM 9-6115-671-14 - Copy (1).pdf" Is blank.
Just thought I would let you know.

 

[Guyfang]

Three phase load. A is 208, B is 105, C is 105. It varies. Sometimes B and C are 195ish. And sometimes when I start it, they are all 208. It's random.

You are taking these readings off the CIM? You need to take them from the load terminals, to be sure.

 

[NDT]

Silly question, why are you paralleling generators when you have a 30 kW generator with 18-30 kW load?
What AMPS are on each phase at 18 and 30 kW?

 

[SCSG-G4]

AMPS is the question, you have been giving us VOLTS. A 30 KW generator is only going to put out 300 AMPS total and to be balanced that needs to be about 100 amps on each circuit (plus or minus 10-15 amps). If they are not balanced, the generator controls shut down the whole thing to protect the machine. That sounds like what is happening. If you don't understand the concept of volts, amps and watts, get someone local that does and know how to get readings, please!

 

[Guyfang]

I was just looking through the TM section of the forum and in your post "All the TM's you need to work on the MEP-805B Generator set"
"TM 9-6115-671-14 - Copy (1).pdf" Is blank.
Just thought I would let you know.

Thats because the Milatary has not coded this TM for public release.

 

[SteveTheGreen]

Silly question, why are you paralleling generators when you have a 30 kW generator with 18-30 kW load?
What AMPS are on each phase at 18 and 30 kW?

During the summer, with everything on, we exceed 30kw. So, we occasionally need two. This being the case, the third one is our spare/backup.

 

[SteveTheGreen]

AMPS is the question, you have been giving us VOLTS. A 30 KW generator is only going to put out 300 AMPS total and to be balanced that needs to be about 100 amps on each circuit (plus or minus 10-15 amps). If they are not balanced, the generator controls shut down the whole thing to protect the machine.

I'll get someone to measure at the CIMs, but.... We've had them balanced and we have not added anything that would change this dramatically. Plus the other machines run fine - as well as rentals we've used recently. So, I don't think it's unbalanced. But I'll check.

I did change out the alternator and 50A circuit breaker to the alternator. Battery charge went up to normal level...27. But still have the under voltage issue. Last remaining issue on this machine!

 

[SteveTheGreen]

Swapped out the voltage regulator fixed the issue. Tightened every wire as well. Its back up and running.