Motor losing power?

Cobra

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I have a Grizzly G0750G lathe and lately the motor is losing power.
Any idea what could be the cause?
 

macardoso

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Looks to me like a 2 HP, 220V, single-phase, 8.5 Amps, 60 Hz, 1725 RPM motor.

First check your connections are tight and utility power is in spec. I've been in a house where the voltage was 30% low for 2 months before they fixed the transformer on the tower.

Next check all the shafts, bearings, etc. to see if anything is binding up and robbing you of tool power.

Finally it could be a failing motor or motor capacitor, but that is unlikely.


How did you come to the conclusion you are losing power? Tool cutting poorly? Could this be a dull tool or mystery metal issue?
 

Cobra

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Losing power because even unloaded, it will no longer spin up at the high rpm settings.
i have had problems with the starting cap. Could this be the running cap?
 

dpb

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Check your belts. Motor might be fine, but belts are slipping.
 

Cobra

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Belts are OK. At moderate rpm (360) you can hear the motor slow with anything over about .010" depth of cut.
 

Tinker2

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Losing power because even unloaded, it will no longer spin up at the high rpm settings.
i have had problems with the starting cap. Could this be the running cap?
Yes. It could be either or both capacitors [run/start caps [if installed]]. Easy to test w/capacitance tester. Inexpensive to replace. If you pull them, make sure to discharge them before touching the posts. They store very high current. Lots of info on the web about handling/testing capacitors.
 

Luc Duchesne

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......Bonjour avez-vous l`information du moteur SVP , je peux vous aider !
 

Cobra

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......Bonjour avez-vous l`information du moteur SVP , je peux vous aider !
Thanks Luc.
It is a 2HP capacitor inductive motor.
It has a starting capacitor and run capacitor.
There is a centrifugal switch to take the starting capacitor out of the circuit.

The motor starts without issue but will not operate the lathe at 1400 rpm but will run the lower speeds.
Even at some lower speeds the motor will slow down with anything over a very light cut.

This afternoon I took it out of the lathe and had a look.
The run capacitor appears to be OK and the start cap looks bad.
The centrifugal switch looks clean and functional.

Jim
 

mksj

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I have replaced the capacitors for others on a number of grizzly motors, also a number of individuals with PM-1236 motors. In addition to those that show obvious swelling or blown up, you cannot tell the function of the capacitor by looking at it, you need to remove it and test it with a LCR meter to look at things like capacitance, ESR and leakage. The specs are also different based on the type/construction of capacitors. I have a Sencore LC103 which tests the capacitors at their rated voltages, it is surprising how many new capacitors sold on eBay test poorly from sitting on the shelf for many years.

The start capacitors are electrolytic and can quickly overheat with frequent start/stops, and also go with age. Often with bulging. leaking or catastrophic failure. The manual specs the start capacitor as 150uF 250VAC. The run capacitors are usually film type and are more durable, the spec. on this lathe is 20uF 450VAC. You might consider replacing both.
 

Tozguy

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I second mkjs' suggestion to replace both capacitors. A weak cap can cause problems with power way beyond what they cost to replace. Caps are consumables, not worth tolerating a suspect one.
 
Last edited:

WalterC

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3rd on replacing both. Since they are cheap- buy a spare.
 

Tim9

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Replace both capacitors and make sure you can hear the starting circuit switching to the run circuit. I have a big old snap on pedestal grinder. The start switch was stuck and it wouldn’t kick out to run. Those windings then quickly overheat and it too would then slow down. I’m amazed it never burned up on me because I was using it like that for a while.
FWIW...I think they make electronic starting switches now which are supposed to be the bees knees. Never used them. Just remember reading about them when fixing my grinder. I was able to repair my switch on my grinder.
 
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