motor start capacitor

[Dan Lenski]

Hi all,
I'm home for the holidays and I was trying to quiet a noisy garage door
opener by greasing the pivots and mechanical parts of the motor. Well,
unfortunately, it looks like I got a bit of grease on the motor as
well. When I turned it on after greasing it, there was a quick puff of
black smoke... after which everything worked just fine for an hour or
two. Then it stopped working and I found that a big huge capacitor had
blown open and leaked a bunch of oily goo.

This is a big "AeroM PSU6430" 64 microF 330VAC capacitor with
spade-type terminals.

I believe nothing else is wrong with the door opener, since the light
comes on and I hear a relay click when I push the button, and the hum
of a transformer, but the motor simply doesn't start.

Does anyone have an idea where I can buy a replacement for such a
capacitor? I couldn't find a clearly compatible part at Digikey, and
local electronics and hardware places have been no help.

Thanks for any help!

Dan Lenski

 

[Roddy Meatstick..............]

Hi all,
I'm home for the holidays and I was trying to quiet a noisy garage door
opener by greasing the pivots and mechanical parts of the motor. Well,
unfortunately, it looks like I got a bit of grease on the motor as
well. When I turned it on after greasing it, there was a quick puff of
black smoke... after which everything worked just fine for an hour or
two. Then it stopped working and I found that a big huge capacitor had
blown open and leaked a bunch of oily goo.

This is a big "AeroM PSU6430" 64 microF 330VAC capacitor with
spade-type terminals.

I believe nothing else is wrong with the door opener, since the light
comes on and I hear a relay click when I push the button, and the hum
of a transformer, but the motor simply doesn't start.

Does anyone have an idea where I can buy a replacement for such a
capacitor? I couldn't find a clearly compatible part at Digikey, and
local electronics and hardware places have been no help.

Thanks for any help!

Dan Lenski

Just look in the yellow pages for 'electric motors' or 'electrical
wholesaler'. They are quite common.
http://www.cpcares.com/capacitors/index.html

 

[Ken Layton]

You should have a local W.W. Grainger Company branch office. If not it
can be ordered online at www.grainger.com and here is the info:

Stock # 4CU62 Motor Start capacitor, 64 UF @ 330VAC $8.32

An electric motor shop may also be able to sell you a replacement cap.
Just bring the old one with you.

 

[Dan Lenski]

You should have a local W.W. Grainger Company branch office. If not it
can be ordered online at www.grainger.com and here is the info:

Stock # 4CU62 Motor Start capacitor, 64 UF @ 330VAC $8.32

An electric motor shop may also be able to sell you a replacement cap.
Just bring the old one with you.

Excellent!!! We do have Grainger here, in fact they sponsor our local
Minor League Baseball team. Thanks a ton, Ken.

Dan

 

[Dan Lenski]

So I've verified that the Lansing, MI grainger carries this capacitor
and I can buy one on Tuesday. Woohoo!

In the mean time I've found that the motor will actually run fine
provided I give it a nudge to get it started. I guess the whole
purpose of the capacitor is to start the electric motor? How does that
work? I don't actually understand how a single-phase AC current can
turn a motor at all... since there's no rotating magnetic field.

Anybody know of a good reference on how an AC motor works?

Dan

 

[Baron]

So I've verified that the Lansing, MI grainger carries this
capacitor
and I can buy one on Tuesday. Woohoo!

In the mean time I've found that the motor will actually run fine
provided I give it a nudge to get it started. I guess the whole
purpose of the capacitor is to start the electric motor? How does
that
work? I don't actually understand how a single-phase AC current can
turn a motor at all... since there's no rotating magnetic field.

Anybody know of a good reference on how an AC motor works?

Dan

The motor has two windings, one of them has the capacitor in series
with it to give a phase shift with respect to the other ! Note if
you want to reverse the motor apply power across the other side of
the cap.

I--@@@@--- L2
I I
L1---I Cap
I I
I--@@@@--- L3

 

[Homer J Simpson]

I'm home for the holidays and I was trying to quiet a noisy garage door
opener by greasing the pivots and mechanical parts of the motor. Well,
unfortunately, it looks like I got a bit of grease on the motor as
well. When I turned it on after greasing it, there was a quick puff of
black smoke... after which everything worked just fine for an hour or
two. Then it stopped working and I found that a big huge capacitor had
blown open and leaked a bunch of oily goo.

Coincidence. It wasn't the grease.

 

[Homer J Simpson]

So I've verified that the Lansing, MI grainger carries this capacitor
and I can buy one on Tuesday. Woohoo!

In the mean time I've found that the motor will actually run fine
provided I give it a nudge to get it started. I guess the whole
purpose of the capacitor is to start the electric motor? How does that
work? I don't actually understand how a single-phase AC current can
turn a motor at all... since there's no rotating magnetic field.

Anybody know of a good reference on how an AC motor works?

Google for (permanent split phase capacitor motor).

 

[Charles Schuler]

Hi all,
I'm home for the holidays and I was trying to quiet a noisy garage door
opener by greasing the pivots and mechanical parts of the motor. Well,
unfortunately, it looks like I got a bit of grease on the motor as
well. When I turned it on after greasing it, there was a quick puff of
black smoke... after which everything worked just fine for an hour or
two. Then it stopped working and I found that a big huge capacitor had
blown open and leaked a bunch of oily goo.

This is a big "AeroM PSU6430" 64 microF 330VAC capacitor with
spade-type terminals.

I believe nothing else is wrong with the door opener, since the light
comes on and I hear a relay click when I push the button, and the hum
of a transformer, but the motor simply doesn't start.

Does anyone have an idea where I can buy a replacement for such a
capacitor? I couldn't find a clearly compatible part at Digikey, and
local electronics and hardware places have been no help.

Was that graphite grease? How much did you get on the motor/electrical
contacts? Seems a bit strange!

 

[Dan Lenski]

Coincidence. It wasn't the grease.

Thanks for relieving my guilty conscience I was beginning to
suspect the same... though it's darned uncanny that it blew immediately
after I greased the mechanical parts.

Once I disassembled the door opener, I realized the capacitor was
hardly in a position to have gotten any grease on it. I looked up the
service life of the capacitor and it's about 16k cycles... meaning it
would last about 12 years if cycled 4 times a day (mom leaves in
morning, dad leaves in morning, mom comes back, dad comes back). And
it's definitely at least 20 years old.

Dan

 

[Dan Lenski]

Was that graphite grease? How much did you get on the motor/electrical
contacts? Seems a bit strange!

It was white lithium grease. Not conductive. I use it on bearings in
bicycles and lab equipment all the time, so I figured it would work
fine on the garage door pivots and the bearings in the motor.

When I sprayed it inside the motor housing, I tried to carefully aim it
only at the mechanical bearings, and NOT at the electrical contacts.

I agree that it's very strange, but the coincidence seems very
unlikely. Although the capacitor was evidently nearing the end of its
service life in any case (16k cycles).

Dan

 

[Sam Goldwasser]

It was white lithium grease. Not conductive. I use it on bearings in
bicycles and lab equipment all the time, so I figured it would work
fine on the garage door pivots and the bearings in the motor.

When I sprayed it inside the motor housing, I tried to carefully aim it
only at the mechanical bearings, and NOT at the electrical contacts.

I agree that it's very strange, but the coincidence seems very
unlikely. Although the capacitor was evidently nearing the end of its
service life in any case (16k cycles).

I'm not convinced that it's a coincidence. If you really sprayed grease
inside the motor, you may have gotten it on the contacts of the centrifugal
switch that is supposed to interrupt the circuit to the start cap once the
motor gets up to speed. If the start cap remains energized for more than
the time needed to start, it will do exactly what you describe quite quickly.

So, at the very least, you should check the AC voltage on the start cap
using a meter that reads only AC (not the DC omponent). It should go to
0 VAC once the motor is turning at normal speed. If not, you'll have to
disassemble the motor and determine what's going on. And have your safety
goggles on while doing it!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Homer J Simpson]

Thanks for relieving my guilty conscience I was beginning to
suspect the same... though it's darned uncanny that it blew immediately
after I greased the mechanical parts.

Don't you hate when that happens?

 

[Homer J Simpson]

I'm not convinced that it's a coincidence. If you really sprayed grease
inside the motor, you may have gotten it on the contacts of the
centrifugal
switch that is supposed to interrupt the circuit to the start cap once the
motor gets up to speed.

Unlikely they use such a motor - more likely a PSC motor with no such
switch. Easy to reverse at speed and there is no great starting load.

 

[Dan Lenski]

I'm not convinced that it's a coincidence. If you really sprayed grease
inside the motor, you may have gotten it on the contacts of the centrifugal
switch that is supposed to interrupt the circuit to the start cap once the
motor gets up to speed. If the start cap remains energized for more than
the time needed to start, it will do exactly what you describe quite quickly.

So, at the very least, you should check the AC voltage on the start cap
using a meter that reads only AC (not the DC omponent). It should go to
0 VAC once the motor is turning at normal speed. If not, you'll have to
disassemble the motor and determine what's going on. And have your safety
goggles on while doing it!

That's a really good point, Sam. I have no idea if this motor has that
type of switch or not. It's a Westinghouse 1/2 hp motor. Is the
switch internal to the motor, or might it be external? If it's
internal, then I really doubt I could have gotten any grease on it...
but if external then I suppose there's a possibility.

In any case I'll buy 2 new caps since they're only $8.

Dan

 

[Sam Goldwasser]

That's a really good point, Sam. I have no idea if this motor has that
type of switch or not. It's a Westinghouse 1/2 hp motor. Is the
switch internal to the motor, or might it be external? If it's
internal, then I really doubt I could have gotten any grease on it...
but if external then I suppose there's a possibility.

In any case I'll buy 2 new caps since they're only $8.

It would be inside the motor, probably at the opposite end from the output
shaft.

Someone else pointed out that he didn't think this was likely in a motor
used for this application but rather a PSC motor. However, then you would
have a motor run cap, not a motor start cap. I don't recall what the
specs were for your cap.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Jamie]

That's a really good point, Sam. I have no idea if this motor has that
type of switch or not. It's a Westinghouse 1/2 hp motor. Is the
switch internal to the motor, or might it be external? If it's
internal, then I really doubt I could have gotten any grease on it...
but if external then I suppose there's a possibility.

In any case I'll buy 2 new caps since they're only $8.

Dan

I've seen a variety of those types of switches.
Air pump driven, Magnetic Drag driven, bearing slip driven etc.
all usually have a return spring or something to force the switch
back into it's starting point again. Most common one's i've seen are
magnetic and get pulled from the shaft when it's spinning. you might
want to pull the back cover off the motor to make sure the mags still
are there or have some life in them. Heat over time can kill them and
thus not switch off the cap also, also a fused set of contacts don't
help;

 

[Baron]

Don't you hate when that happens?

Yea ! Like when you do a clean re-install on a computer, set it up
just right........... then the hard drive fails !*@$"£@

 

[Ken Weitzel]

I've seen a variety of those types of switches.
Air pump driven, Magnetic Drag driven, bearing slip driven etc.
all usually have a return spring or something to force the switch
back into it's starting point again. Most common one's i've seen are
magnetic and get pulled from the shaft when it's spinning. you might
want to pull the back cover off the motor to make sure the mags still
are there or have some life in them. Heat over time can kill them and
thus not switch off the cap also, also a fused set of contacts don't
help;

Hi...

Might even be a simple centrifugal switch, in which case grease might
be enough to bind it up.

Take care.

Ken

PS - REAL programmers use copy con.

 

[Jamie]

Hi...

Might even be a simple centrifugal switch, in which case grease might
be enough to bind it up.

Take care.

Ken

PS - REAL programmers use copy con.

i thought they used a numerical HEX entry key board!