Generator Problems

[wozz]

Picked up a cheap 110v genny the other day the engine is worth far more than I paid for the whole thing so no loss. But now it's having problems.

After running it With a load smoke started coming from the alternator. took it apart, smoke coming from the top of the capacitor (solder melted) and yellow goo rising out of the transformer core. Anyone know the cause of this and any possible fixes?

Cheers

 

[bryanh]

First off replace the capacitor well thats what I would do

 

[OnOff]

Assuming you didn't overload it then ensure it's running smooth for a start i.e. not lumpy with wide speed variations. Make sure you replace with a decent new capacitor, higher working voltage if possible and make sure it's MOTOR rated. Also that the crimped 1/4" spades are on nice and tight i.e. good connection to the cap.

 

[wozz]

Deffo not overloaded, and engine running lovely. Would a defective cap cause the transformer to go into melt down?

Will start trawling for a new cap!

Thanks for the input lads

 

[Marvo]

If the goo coming from the transformer is the shellac varnish from the windings then it was almost certainly overload. It might have been an internal problem that caused the overload not necessarily something you had plugged in. Ylu could just try replacing the cap, if you're really lucky the rest of the damage that's evident may be superficial but I wouldn't hold out too much hope.

 

[wozz]

So the cap goes into melt down shorts causes a overload warming the core and melting the varnish.

This may sound silly but what exactly would the cap be doing? It looks like its connected before the core so out of the alternator? Would it be there to smooth the output? (I'm sure the electronic minded people that are reading this are cringing!)

I will try to upload some pictures.

 

[Marvo]

The cap might be part of a smoothing or filter circuit. Can you attach a couple of pictures of the damage, it might give us more of a clue?

 

[wozz]

Will do tonight as on the phone at the moment and don't think I can upload from it.

 

[wozz]

had problems up loading wouldnt accept any of them so created a photobucket thing. Hope this works!

 

[wozz]

phew! so looks like I need one of these:

where is best to get one?

 

[Marvo]

Maybe one more photo from a slightly greater distance so we can see the whole layout in one shot.

There's a few nasty looking crimp connections on some of those lugs/terminals. Also is that DIN rail digging into the top of the transformer windings or does it just look that way because of the angle of the photo?

 

[wozz]

not sure if the DIN rail is touching does look close. I will get a few more photos for you tomorrow layout not easy to make out most wiring dives through the bottom into the alternator. A few of the terminals are a bit ropey.

 

[wozz]

is this what i need? http://cpc.farnell.com/1/1/27683-capacitor-50uf-450vac-tab-4-16-10-30-64-ducati.html

 

[Marvo]

http://uk.farnell.com/genteq/97f5211/capacitor-pp-film-50uf-440v-6-qc/dp/1338198 Might be a better option, it should have better heat dissipation. I would shop around though, 27 pounds sounds expensive for a 50uF capacitor.

 

[wozz]

Your input is very much appreciated Marvo.

Thats very good of you Canoe, I will get a PM to you, its push on terminals.

Looking to learn a bit more, so caps can fail OC or SC, if they fail OC will this stop the genny working? or would this depend on the layout of the particular alternator?

 

[Marvo]

Yep caps can go short circuit but if nothing trips they usually overheat very shortly afterward and go bang which generally leaves then open circuit. I'm still not sure what that cap is for, at first I thought it might be for excitation but that's less likely if it's only got 2 terminals. Does the generator have carbon brushes on the rotor?

The cap could also be part of the voltage regulation system (AVR) without more info it's just a guess.

*Edit* I would also strongly suggest you investigate that DIN rail resting on the top of the transformer. Remove it and check if the copper windings are damaged.

 

[wozz]

She is back up and running! Only had it going at short time but ran a hilti drill no problem engine doesnt stumble or even change note. No where near a big load though its rated for 4Kw and has a 13HP engine.

Thanks to canoe boy send the paperwork over mate.

I will re do the crimps that look a bit dodgy. I think the din rail is just short of the windings certainly no damage there.

Had a quick play around with no capacitor not connected the output was 14V. Havnt been right inside it yet so no idea about the brushes.