MEP-006 stator fried at 480 - what would cause???

[bimota]

First military generator I've sold to get returned - customer tells me he moved voltage board to run a 480 pump and the stator and voltage regulator burned up. Wants his money back....unfortunately I've already restocked my inventory, so I really want to find out how and why this happened. I sold a dozen refurbished machines last year without even a tickle of a problem other than guiding a customer thru a wiring issue.

So this is a mystery - unit was load tested to 50kw at 208 wye for several hours prior to deployment. So it left the yard working solid at 208 - 50kw. It's coming back in this afternoon so I'll finally get a look at it.

So if you are knowledgeable in generator theory - what could cause a stator and regulator to burn up? Why did the unit not self protect? My guess is that the unit was overloaded by running low voltage (416 instead of 480) and possibly low frequency causing the stator to slowly heat up without releasing the breaker. Since these are manual machines this setup is easily done but would that cause the stator to heat without protecting? Experienced thoughts?

 

[R Racing]

did he wire it correctly when he switched it to 480? normally 480 is delta. and 208 is wye.

 

[Keith_J]

Insulation breakdown due to higher voltage? Causing arcing to ground? Since this is before circuit breakers, current jump would cause the VR to go to rail, burning that out too.

 

[bimota]

Ok, customer brought the unit in today - showed me the stator inspection cover and the "copper" showing on the winding. I said that that looked ok and that a burnt stator would show smoke and smudge. So I won't announce yet the generator repair guy who charged these customer $600 to tell them the stator and regulator was burnt annd that the unit had thousands and thousands of hours on it when the hour meter read 98.

Later the same day I decided ok, let's fire it up and see. It fired up and immediately went to 480 volts on the front meter. I took out my digital meter, closed the breaker and measure precisely 277 on L1, 273 on L2 and 265 on L3. To me and those like me that is 480 Wye - anyone want to argue?

Point is a "trained" electrician installed the unit, a "trained" and expensive generator repair man charged $600 to tell the customer that the unit was burned up and the whole fricking issues was they did not hold the start switch long enough for the excitor to work.

How do I beat these people - WTF? Huge trouble and loss by "trained" professionals.

 

[R Racing]

Sounds like a very incompetent electrician to me . If it did burn up the smell would be unbearable. On the old windings they would lacquer the windings in a brownish clear coat. Makes me wonder if the guy had ever seen a older gen before.

 

[Keith_J]

480 burning the windings will also let a lot of magic smoke out. These are epoxy dipped which locks the windings in place as they are subject to serious mechanical stress in operation.

Want to to bet that tech was on commission for any new sales leads?

 

[bimota]

So how would you play this? I'm pissed off, wasted a lot of time doing analysis, determining and writing up options for the customer, I even started working on a replacement generator. So first off I can punish the customer for hiring incompetents by telling them they will need to pay but I also want to consider hammering the incompetents. Writing up a receipt showing catastrophic generator failure when no such failure existed could be a sort of fraud; though we don't know if it was incompetence or intentional.

So both parties working on the generator at the site are licensed contractors - there is a complaint process where you can file against someones license. What do you think - take it that far? Suggestions, I now have a perfectly working MEP-006 in my yard that I don't have space for and another one being prepped up. These are great machines but they don't sell every week!

 

[R Racing]

I myself would show the customer that his electrician wrong! Id also show him that it works like its suppose to and that due to the lack of his electricians knowledge that it has both cost him and you money. Give him confidence in the gen you are selling him. And tell him how his guy made a fool out of him. Let him handle it from there . No 1 likes to be made a fool !! And I'm sure he will take it from there.