What makes ,motor capicitors explode(literally!)

[Pindecked]

I've been around the 70's since 1975 & had never had this happen 'before'...

I've had this happen twice within the last year..the first time,I had the wireway cover off,& was right there when it went! Right in the face ! paper all over the place.What a taste in my mouth !!! YUK !

Last night, a machine stopped (no cycle start),as I ran down back,we heard a loud whistle, then a bang (like a skyrocket).SMOKE all around the machine ...kinda cute really,as I didn't get this one in the face.

Both times it was the sweep cap.

What gives???
Thanks

[8270king]

Re: What makes ,motor capicitors explode(literally!)

Electronics is not my strong suit but it might have something to do with the screws backing out or being loose. I recall a blown one with a loose screw.

king

[GPS]

Re: What makes ,motor capicitors explode(literally!)

Hey Pindecked, I have had the same problem a few times. If you use a cheap set of sweep relay contactor points (I think we all know the brand) sometimes the uppers will become dislodged and turn sideways making contact. Your bottom contacts are also making contact. So lets see...the uppers make the motor run, the bottom contacts make the motor stop and both are making contact. Check it out and let us know. Good luck.

[JJP]

Re: What makes ,motor capicitors explode(literally!)

When capacitors are installed the white vent cap should be at 12:00.If not this could cause them to explode.

[Coors]

Re: What makes ,motor capicitors explode(literally!)

i agree with GPS. The only one ive seen explode was caused by contacts in the chassis

[Jimmy Jam]

Re: What makes ,motor capicitors explode(literally!)

Usually its caused by the centrifugal switch points not opening. They can ark shut if you have a bad resistor, contact points, wires or terminal connections ( motor draws more juice) or they can stay closed if the cent. mech. was not installed down far enough.
Unless you use VANTAGE UPPERS!

I don't know why they explode but if you've ever taken one apart you probably noticed how small the wire is. Kind of like a light bulb filament. Have you ever exploded a 12v lamp by accidentally running 110v to it? I think that's what kind of happens to the cap..
Knot sure though.

Jonas

[Ed Fox]

Re: What makes ,motor capicitors explode(literally!)

If the centrifugal switch fails to open after moter start the capacitors will blow! One other thing that was mentioned on here was the vent holes, I have talked to alot of people that dont know they exist. With the 70's make shure the vent hole is on top(12:00) when the place the caps in the retainer. With the 30's you want to make shure when you install the caps in the covers that the vent holes are against the head. This dosnt cause them to explode but will cause excssive heat build up and premature failure.
Ed

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[Dutch]

Re: What makes ,motor capicitors explode(literally!)

I agree with GPS & Coors. That’s definitely the most common cause. We use electronic start switches on our motors, so I don’t have much experience with centrificals.
While we’re on the subject of contacts, does ANYONE still sell the good contacts? We’ve ordered from a couple of different places & all we keep getting are the crappy (You know who) ones.
Dutch

[felix]

Re: What makes ,motor capicitors explode(literally!)

forget those contacts and put in a siemens relay,you wont regret it.

[Ed Fox]

Re: What makes ,motor capicitors explode(literally!)

Forget the mech. contactors and check out the S/S contactors from BowlTronics, very reliable!
Ed

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[Jimmy Jam]

Re: What makes ,motor capicitors explode(literally!)

Forget the S/S BowlTronics and switch to FUGI's bipolar transistor module used in robotic manufacturing.

[felix]

Re: What makes ,motor capicitors explode(literally!)

where do i get one of those fugi's jonas?

[Ed Fox]

Re: What makes ,motor capicitors explode(literally!)

Yes, please where and how much?
Ed

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[Dutch]

Re: What makes ,motor capicitors explode(literally!)

Jonas,
You're teasing us. How 'bout more info?
Are you using them & for how long?
Dutch

[Jimmy Jam]

Re: What makes ,motor capicitors explode(literally!)

Sorry guys,
I was just going with the flow of the posts. I had to find something better then the Bowltronics to post so I chose the FUGI. I have an article about it in a 1995 IEEE magazine. It looks fairly small and is rated at 1200v 400A, used for robot control in automotive manufacturing. No price given, its probably cost an arm and a leg.

If I had money to burn I would buy those mercury contactors listed in the Grainger book. It sounds like they last forever.

Back to reality.....I've been testing the BowlTronics in two chassis for a couple of years now and haven't had a problem with them. So far so good.

Theres about 100 different web pages about exploding capacitors by the way.

Good call Dutch!

Jonas