120VAC 15A motor won't spin up to speed

[Michael Kennedy]

I have a 120VAC 15A electric motor that is on an aircompressor that I found.
I plugged it in and the motor starts to spin slowly but never gets going
fast then trips the circuit breaker.

It spins eaisly by hand and the bearings seem to be okay. Does it probably
just need new capacitors? It has 2 120v 330uf caps on it.


- Mike

 

[Michael Kennedy]

I forgot to mention that it trips the breaker in 15 seconds or less.

 

[Michael Kennedy]

There is no belt, the shaft goes right into the compressor. I can turn it
quite eaisly with my hand.

- Mike

 

[Michael Kennedy]

I'm thinking starter cap and possibly the run cap since they don't look very
pretty. I just have no idea what sympoms a motor suffers from when it has a
bad start cap..

I guess I'll check the caps with my esr meter.

- Mike

 

[Homer J Simpson]

I have a 120VAC 15A electric motor that is on an aircompressor that I
found. I plugged it in and the motor starts to spin slowly but never gets
going fast then trips the circuit breaker.

It spins eaisly by hand and the bearings seem to be okay. Does it probably
just need new capacitors? It has 2 120v 330uf caps on it.

If those are the correct ratings, possibly. But I'd check the windings with
a meter first.

 

[Homer J Simpson]

I'm thinking starter cap and possibly the run cap since they don't look
very pretty. I just have no idea what sympoms a motor suffers from when it
has a bad start cap..

Won't run. Buzzes. Starts up very slowly. Halts and catches fire.


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| | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__|
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|_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_|
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___ | |_ | |_) | ___ _ __ __ _
/ _ \| _| | _ < / _ \| '__/ _` |
| (_) | | | |_) | (_) | | | (_| |_
\___/|_| |____/ \___/|_| \__, (_)
__/ |
|___/

 

[Michael Kennedy]

Won't run. Buzzes. Starts up very slowly. Halts and catches fire.

hmm.. sounds about right.. Off to go buy some caps tomorrow.

Thanks

- Mike

 

[Michael Kennedy]

How do you determine what value cap you need by checking the windings with a
meter?

Upon closer inspection there is one 330mfd and one rusty cap that I can't
read.

 

[Jamie]

I have a 120VAC 15A electric motor that is on an aircompressor that I found.
I plugged it in and the motor starts to spin slowly but never gets going
fast then trips the circuit breaker.

It spins eaisly by hand and the bearings seem to be okay. Does it probably
just need new capacitors? It has 2 120v 330uf caps on it.


- Mike

starting winding bad, centrifugal switch bad? starting cap
(if you have one) bad ?
who knows?

 

[Jamie]

I forgot to mention that it trips the breaker in 15 seconds or less.

pull the belt off and see if it comes up to speed.

 

[Homer J Simpson]

How do you determine what value cap you need by checking the windings with
a meter?

Upon closer inspection there is one 330mfd and one rusty cap that I can't
read.

You don't, but if a winding is burned out new caps won't help. BTW, you
might have a motor with a start and a run cap. Local distributor may be able
to guess at the value - many electrician's meters now will measure the value
too.


--
_____ _ _
|_ _| | | | |
| | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __
| | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__|
_| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ |
|_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_|
__ ____
/ _| | _ \
___ | |_ | |_) | ___ _ __ __ _
/ _ \| _| | _ < / _ \| '__/ _` |
| (_) | | | |_) | (_) | | | (_| |_
\___/|_| |____/ \___/|_| \__, (_)
__/ |
|___/

 

[Sam Goldwasser]

How do you determine what value cap you need by checking the windings with a
meter?

Upon closer inspection there is one 330mfd and one rusty cap that I can't
read.

Remove all load from the motor shaft.

Disconnect everything but the run winding. Spin the rotor by hand and
power up the motor. It should come up to speed instantly and run cool.

If this works, the rotor and windings are probably OK.

If it cannot be spun up, buzzes, still catches fire , one of the windings
may be shorted. Another alternative is that the bearings are so shot
that it's binding on the stator.

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[Ken Weitzel]

Remove all load from the motor shaft.

Disconnect everything but the run winding. Spin the rotor by hand and
power up the motor. It should come up to speed instantly and run cool.

If this works, the rotor and windings are probably OK.

If it cannot be spun up, buzzes, still catches fire , one of the windings
may be shorted. Another alternative is that the bearings are so shot
that it's binding on the stator.

Hi...

You guys are creating flashbacks for me... back to
around the time sunshine was invented

Anyone else here long enough in the tooth to
remember the "growler"?

Take care.

Ken

 

[Homer J Simpson]

You guys are creating flashbacks for me... back to
around the time sunshine was invented

Anyone else here long enough in the tooth to
remember the "growler"?

Sure - and the vibrating hacksaw blade.



--
_____ _ _
|_ _| | | | |
| | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __
| | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__|
_| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ |
|_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_|
__ ____
/ _| | _ \
___ | |_ | |_) | ___ _ __ __ _
/ _ \| _| | _ < / _ \| '__/ _` |
| (_) | | | |_) | (_) | | | (_| |_
\___/|_| |____/ \___/|_| \__, (_)
__/ |
|___/

 

[Michael Kennedy]

Hmm.. Well I don't know what you guys are talking about but anyhow a new cap
fixed the motor! Thanks evrybody.

Now I found out that the piston ring on the air compressor is bad and it
also needs a new piston sleeve. Can you get piston rings and sleves for
these things? I dindn't find much on google.

- Mike