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Sizing a Bench Grinder Capacitor

L

leoJ

Jan 1, 1970
0
Have a bench grinder that was given to me and runs fine if you spin it
up by hand - the capacitor is missing. Is there a way to determine what
size/part no. capacitor will work with a 115V 60Hz Single Phase motor?

Thanks in advance.
 
H

Homer J Simpson

Jan 1, 1970
0
Have a bench grinder that was given to me and runs fine if you spin it
up by hand - the capacitor is missing. Is there a way to determine what
size/part no. capacitor will work with a 115V 60Hz Single Phase motor?

HP?
 
S

Sam Goldwasser

Jan 1, 1970
0
w9gb said:
Likely a motor start capacitor.
http://www.cde.com/new/catalog/motorstart/

CDE motor start capacitor catalog page (download this - right mouse click -
Adobe Acrobat)
http://www.cde.com/catalogs/PSU.pdf

I am looking at a NOS Mallory motor start capacitor on my bench --
it is rated at: 108-130 mfd at 250 VAC

Application Guide
http://www.cde.com/catalogs/AEappGUIDE.pdf

If it's used only for starting.

Easiest test would be to spin it up by hand and then use a multimeter
to check for voltage across the wires where the cap would go. If you
see full line voltage, it's a run 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.
 
M

me

Jan 1, 1970
0
If it's used only for starting.

Easiest test would be to spin it up by hand and then use a multimeter
to check for voltage across the wires where the cap would go. If you
see full line voltage, it's a run cap.

snip waste text
Most bench grinders I've seen use a motor run capacitor.
 
J

James Sweet

Jan 1, 1970
0
me said:
Most bench grinders I've seen use a motor run capacitor.


But if he has to spin it to start it, that would imply it's just a
starting capacitor. Can you hear an audible click as it picks up speed
and again just as it slows to a stop?
 
W

w9gb

Jan 1, 1970
0
leoJ said:
Have a bench grinder that was given to me and runs fine if you spin it
up by hand - the capacitor is missing. Is there a way to determine what
size/part no. capacitor will work with a 115V 60Hz Single Phase motor?

Thanks in advance.

Do you have a mfg. or model number for this bench grinder?

gb
 
S

Sam Goldwasser

Jan 1, 1970
0
James Sweet said:
But if he has to spin it to start it, that would imply it's just a
starting capacitor. Can you hear an audible click as it picks up speed
and again just as it slows to a stop?

No, a split phase induction motor with an open or missing cap will not
start regardless of whether it is a start or run cap. Spinning by hand
will get it going (assuming minimal load).

An induction motor designed to have a run cap will still run without one
if started manually but won't have rated torque.

An induction motor designed to have a start cap will still run without
one if started manually and will have rated torque.

The main functional difference is that the start cap is not rated for
continuous operation and is removed from the circuit once the motor
reaches about 75 percent of operating speed.

--- 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.
 
N

nowan

Jan 1, 1970
0
Central Machinery Industrial #36127 is what it says on the label.
 
N

nowan

Jan 1, 1970
0
Hope this doesn't end up getting posted 3 times - having trouble
sending....

Central Machinery Industrial #36127
 
M

Michael A. Terrell

Jan 1, 1970
0
nowan said:
Hope this doesn't end up getting posted 3 times - having trouble
sending....

Central Machinery Industrial #36127


Central Machinery is sold by Harbor Freight Tools, Inc. They may
still have the manual on file.

http://www.harborfreight.com/


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
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