Blown capacitor replacement

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Old 06-30-15, 05:26 PM
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Blown capacitor replacement

So I was working in my shop and had the dust collector running for about a half hour or so and began to smell something burning. After shuting a few things down and doing some investigating I found it was coming from the dust collector which is in a small building outside my shop.

You can see the damage from the pics below. My question is what other damage besides the blown capacitor could there be? Is this ABS 100MFD 100uF 250V AC Motor Starting Capacitor: Amazon.com: Industrial & Scientific the right replacement? I assume the replacement procedure is pretty stright forward?

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Old 06-30-15, 07:05 PM
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It's hard to say if any damage was caused. Not usually. The cap gets dried out and goes leaky. It could allow the start winding to stay energized when it shouldn't be. You won't know for sure until you restart the motor.

It looks like that motor has two caps. Probably wouldn't hurt to replace them both. Your linked to part looks to be ok.
 
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Old 06-30-15, 07:24 PM
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The cap in the pic is the good one, I can't find any writing on the blown one, but I assume it would be the same type? I was wondering if it might be a run capacitor. I don't know alot about these types of motors, would they have two start capacitors?

The motor did start up and run with the blown cap. I turned it on to see if I could see what the problem was and that's when I heard/seen a pop under the cover for that one.
 
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Old 06-30-15, 09:04 PM
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More than likely the bad cap is a run cap. It won't be the same ratings.

A start cap is usually rated close to operating voltage.... like 250vac and when I compute the value for your start cap I get 90mfd which means the 100mfd is your start cap.

The run cap, which is always connected, should be a 370v cap and a low mfd value. What value I'm not sure I can figure out. A run cap basically shifts the frequency of one of the windings so the motor runs smoother.

The run cap for a 3hp motor should be around 20mfd. The exact value is set by the motor mfg.
 
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Old 07-01-15, 04:43 AM
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Here is the info for the burnt out cap. It was on the bottom of it.

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One more question. What should this motor be fused at? . I was told by an electrican 20 amps due to the start up draw. Is that right?
 
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Old 07-01-15, 05:46 AM
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What data is on the data plate on the motor?
 
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Old 07-01-15, 08:40 AM
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Just what is shown in the pic in the first post.
 
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Old 07-02-15, 02:54 PM
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So I am ordering this capacitor to replace the blown one, can someone please confirm that it is the right one?

Run Capacitor
http://www.amazon.ca/CBB60-Polypropy...bb60+450v+35uf
 
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Old 07-02-15, 05:05 PM
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The data is 7.8A at 240vac. A 15A may hold. If not then you would need a 20A breaker.

Looks good on the cap. Higher voltage spec is good.
 
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