Electric motor question

[Cougar]

Have a 1/2hp motor.
Starts and runs fine under no load.
But the slightest load, it's starts but runs at lower RPM then trips.
My thought is the start capacitor.
What do you all think.

Thanks

 

[930dreamer]

Run capacitor?

 

[Cougar]

They put a bigger pulley on the motor, say it runs fine now.
That doesn't make any sense.

 

[mark-NJ]

It could make sense....

It's a 1/2hp motor. If it was being asked to do more work than that, the result would be what you observed: slow down, draw too much current, trip the breaker.

Change the pulley sizes to a different ratio and the motor is asked to work less.

 

[Cougar]

Wouldn't the bigger pulley make it work harder.

 

[mark-NJ]

bigger on the motor + same (or smaller) on the driven shaft = less work.

Think of it like riding a 10-speed bike. Starting off with a big pedal sprocket + small wheel sprocket = easy. By contrast, small pedal sprocket + big wheel sprocket = hard

 

[AP514]

Good example Mark-NJ....+1

 

[Dagny]

wired for 240 running on120

 

[Cougar]

bigger on the motor + same (or smaller) on the driven shaft = less work.

Think of it like riding a 10-speed bike. Starting off with a big pedal sprocket + small wheel sprocket = easy. By contrast, small pedal sprocket + big wheel sprocket = hard

You have it backwards.
Try starting out in 10th on a ten speed bike.

wired for 240 running on120

Thought about that, but haven't had a chance to check.

 

[DeeKay]

Yeah that analogy is totally backwards, a smaller drive pulley would allow the motor to not work as hard and in turn slow down the load. Maybe they meant they installed a larger driven pulley and left the drive the same? That would make more sense.

+1 for 240 running on 120
Is this a dual cap motor? Or just the start capacitor?

 

[larry_g]

I ran into that problem on a table saw and it turned out to be dry bushings on the motor shaft. A bit of oil and it runs like it should.

lg
no neat sig line

 

[nadogail]

Over Load or Lack of Lubrcation

 

[Cougar]

Yeah that analogy is totally backwards, a smaller drive pulley would allow the motor to not work as hard and in turn slow down the load. Maybe they meant they installed a larger driven pulley and left the drive the same? That would make more sense.

+1 for 240 running on 120
Is this a dual cap motor? Or just the start capacitor?

They said bigger pully on the motor.
I will check it when I'm there Friday.

 

[Cougar]

Thanks for the replies.

 

[Cougar]

Yeah that analogy is totally backwards, a smaller drive pulley would allow the motor to not work as hard and in turn slow down the load. Maybe they meant they installed a larger driven pulley and left the drive the same? That would make more sense.

+1 for 240 running on 120
Is this a dual cap motor? Or just the start capacitor?

It's a dual cap.

 

[DeeKay]

It's a dual cap.

Sounds like a bad or dying run cap. OR could have been a bad connection somewhere and when they changed the pulley maybe bumped the bad connection which allowed it to run fine after the pulley change. Grasping at straws here trying to make sense of the pulley swap

 

[dls]

Bigger pulley makes motor run slower, increasing charge time for run capacitor on PSC motor. Capacitors charge over time and discharge almost immediately.

 

[Innovate1]

Bigger pulley makes motor run slower, increasing charge time for run capacitor on PSC motor. Capacitors charge over time and discharge almost immediately.

um... no. The caps are going to charge and discharge ever half cycle of the power line no matter how fast the shaft turns.

I would check the caps. Probably one or both sections low value or open. May not be it but it's the first thing I would check. Failures are common.

Pulley swap doesn't make sense. Wondering if they swapped the load pulley instead or that description got mixed up in some way...