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Subject Author Date
Electric Motor Problem <mikosh6 01-26-2007
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Posted by on January 26, 2007, 9:44 pm


I noticed that our central vac didn't sound right today. I took the plastic
housing off the top of the motor so the commutator and brushes were visible
and started it up. After a few seconds of operation I start to see the blue
spark between the brushes and commutator start to extend almost 1/2" in the
direction of rotation around the commutator. As this happens the speed of
the motor slowly begins to drop. The motor was overhauled last April; new
bearings and brushes.The vacuum is 22 yrs old so the commutator on the motor
has seen a lot of wear but it looks in reasonable shape. Anybody have an
idea what might be happening here?
Thanks,
Mike
--
mikosh6@-NOSPAM-yahoo.com
Remove -NOSPAM- to email please.



Posted by Eric on January 26, 2007, 9:59 pm


mikosh6@-NOSPAM-yahoo.com wrote:

> I noticed that our central vac didn't sound right today. I took the
> plastic housing off the top of the motor so the commutator and brushes
> were visible and started it up. After a few seconds of operation I start
> to see the blue spark between the brushes and commutator start to extend
> almost 1/2" in the direction of rotation around the commutator. As this
> happens the speed of the motor slowly begins to drop. The motor was
> overhauled last April; new bearings and brushes.The vacuum is 22 yrs old
> so the commutator on the motor has seen a lot of wear but it looks in
> reasonable shape. Anybody have an idea what might be happening here?
> Thanks,
> Mike

You might need to clean out the slots on the commutator
Also, make sure the brushes are the correct ones and have proper tension.
Eric

Posted by mm on January 26, 2007, 11:45 pm



>mikosh6@-NOSPAM-yahoo.com wrote:
>
>> I noticed that our central vac didn't sound right today. I took the
>> plastic housing off the top of the motor so the commutator and brushes
>> were visible and started it up. After a few seconds of operation I start
>> to see the blue spark between the brushes and commutator start to extend
>> almost 1/2" in the direction of rotation around the commutator. As this
>> happens the speed of the motor slowly begins to drop. The motor was
>> overhauled last April; new bearings and brushes.The vacuum is 22 yrs old
>> so the commutator on the motor has seen a lot of wear but it looks in
>> reasonable shape. Anybody have an idea what might be happening here?
>> Thanks,
>> Mike
>
>You might need to clean out the slots on the commutator

They used to say to "undercut the mica". Does that still apply? Did
the overhauler do that last April? The mica is the stuff between the
copper segments. When the copper wears down, the mica has to be cut
down, I guess.

>Also, make sure the brushes are the correct ones and have proper tension.
>Eric


Posted by Joe on January 26, 2007, 10:20 pm


> I noticed that our central vac didn't sound right today. I took the plastic
> housing off the top of the motor so the commutator and brushes were visible
> and started it up. After a few seconds of operation I start to see the blue
> spark between the brushes and commutator start to extend almost 1/2" in the
> direction of rotation around the commutator. As this happens the speed of
> the motor slowly begins to drop. The motor was overhauled last April; new
> bearings and brushes.The vacuum is 22 yrs old so the commutator on the motor
> has seen a lot of wear but it looks in reasonable shape. Anybody have an
> idea what might be happening here?

Adding to Eric's commen\ts, the overhaul should also have included
truing and smoothing the commutator. My bet is on wrong brush type for
the unit. Central vacs are robust machines that can draw considerable
current and require a high conductivity brush and maximum commutator
contact. The proper brush may even need considerable copper content
like those in auto starter motors. A set of OEM brushes might help the
problem. HTH

Joe


Posted by Steve Barker on January 26, 2007, 10:53 pm


Sounds like the brush springs are weak.

--
Steve Barker


>I noticed that our central vac didn't sound right today. I took the plastic
>housing off the top of the motor so the commutator and brushes were visible
>and started it up. After a few seconds of operation I start to see the blue
>spark between the brushes and commutator start to extend almost 1/2" in the
>direction of rotation around the commutator. As this happens the speed of
>the motor slowly begins to drop. The motor was overhauled last April; new
>bearings and brushes.The vacuum is 22 yrs old so the commutator on the
>motor has seen a lot of wear but it looks in reasonable shape. Anybody have
>an idea what might be happening here?
> Thanks,
> Mike
> --
> mikosh6@-NOSPAM-yahoo.com
> Remove -NOSPAM- to email please.
>



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