Mep803a trips breaker at 6000w

[Korgoth1]

I recently got an 803a that looks to be in good shape, I would guess around 2000 hrs based on the paint. It runs good but trips the main breaker and lights the overload lamp after 10 minutes at 6000w. Have any of you guys ran into this problem or know where I could start? I have looked at the schematics trying to find an adjustment with no luck...

With the set loaded to 6000w, around 25amp per leg, I am getting 8vac off current transformer 3, the other two nothing. Am I correct to assume only CT3 is used during 120/240 single phase?

 

[kloppk]

I noticed on my 802 that the %Load meter was reading oddly high for a given load.
Turns out the contacts in the load reconnection switch that had to do with connecting the "burden" resistors to the current transformers weren't making good contact. Due to the added resistance from the poor contact the voltage that the current transformers put out was abnormally high making the generator "think" it had a greater load on it than it actually had. I just had to exercise the A/V selector switch a few time and it cleared up the problem. Moving it thru the different positions scuffed up the switch's contacts enough so that they made good contact and now it's reading the current %Load. Only do this with the generator OFF.
Might be what's making your contactor to trip out.

During my investigation I calculated on my 802 the voltage across CT3 with a 133% 240 VAC load would be 7.5 volts.
Not sure what it would be for the 803. Depends on the 803 current transformer used, the number of loops thru the current transformer and the burden resistance across the current transformer.

 

[Korgoth1]

My load reconnection switch(am/vm) might be spotty because I cycled it a couple turns and my volt meter quit working, so that switch is used in the breaker trip circuit? The burden resistors are used aswell? Because two of my burden resistors measure 1 ohm instead of 7.5...

 

[Korgoth1]

According to the TM, if I read it correctly, you Do Not have to desolder the burden resistors to test them.

 

[kloppk]

Sounds like you AM/VM switch is spotty.
The burden resistors and current transformers have no effect on the voltmeters operation. Part of the AM/VM switch switch's the burden resistors and %Load meter. A separate part of the switch controls the Voltmeter.

 

[Korgoth1]

I took some time today and tested the current transformers, had continuity on each, so they are good. I then desoldered and tested the burden resistors and they all had 7.5-7.8 ohms, so theyre good.

I looked up the S6 circuit schedule in the TM, so I could ohm test the AM/VM, and just my luck the knob broke off while trying to switch!

Right now I don't need the three phase capability, I wonder if I could use the circuit schedule and wiring diagram, and a terminal board from lowes to "hardwire" the unit in single phase 120/240? All the switch does is connect the odd numbers to evens, and has a few internal and 2 external jumpers. According to the circuit schedule, the switch, in 1 Phase L1-L3, connects:

1-2 15-16 31-32
7-8 17-18 27-28
9-10

This would mean:

(1-2) 170B, 167G, 167E, 167F

(7-8 ) 176A, 176B, 169B

(9-10) 168B, 167E, 162G, 167F

(15-16) 172A, 003M

(17-18 ) 177A, 001E

(27-28 ) 163A, 167F

(31-32) 175A, 171A

Which may get me going until I can find a switch.

 

[Korgoth1]

Well, I managed to get the switch in the correct position with the nub that was left and tested the AM/VM. It is reading correct, so I'm going to try and reinstall it, hopefully it will pull full load now...

 

[kloppk]

Hopefully it'll work for you now. Keep us posted on how you make out.
The master switch and the AM/VM switch's are notorious for having the plastic shafts break on them.
My 802 came with a broken master switch. Replaced it with a steel shaft version.

 

[Korgoth1]

Does gmg sell the metal shaft version, or where can I find one?

 

[Korgoth1]

Well, it still trips the breaker and lights the overload lamp. I flipped the battle short and ran it a few hours with 11kw on it, ran great and started running cleaner. I guess I need to test the overload/short circuit relay now...

 

[Korgoth1]

Just to confirm, I'm suppose to have 4 turns around the Current transformers correct?

 

[kloppk]

TM-9-6115-642-24 PDF page 277 indicates that each wire passed thru the CT's 4 time. There should be two wires looping 4 times thru each CT opening.

 

[Korgoth1]

Does anyone know the part number off the 802a and 803a's Current Transformer? I dug through TM-9-6115-642-24P, but could not find it, it was pictured, but not listed, only it's screws...

 

[kloppk]

The 802 uses P/N 88-21132 Cage Code 60177
The 803 uses the same current transformer as the 802
It's listed on in the TM on PDF page 51 item 36
I believe it's made by Technology Research. Their P/N is 19460