Motor clicks under load

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Mrehder
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Posts: 8
Joined: Sun Sep 13, 2020 8:17 am

Re: Motor clicks under load

Post by Mrehder »

My apologies for the pause here (life intervened).
I had decided that the problem was bent motor sheave tines.
I purchased what I thought was a dead-motor markV in order to get the sheeves.
It turns out this had a 240v motor and the problem was a broken tab on the lower shaft eccentric adjustment.
I extracted the working motor and put it into my markV.
I still had the same problem - after “U” the headstock cycles with a click.
I then went back to the “dead” system and replaced the headstock chassis to get a working headstock. I then reinstalled the original 240v motor in this system.
The same cycling problem occurred at speed “U”.
So the problem seems to be endemic to these 240v motors.
Mrehder
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Joined: Sun Sep 13, 2020 8:17 am

Re: Motor clicks under load

Post by Mrehder »

And further…
I connected a belt sander, putting the motor under load, and it labors, clicking in and out.

I think I understand now that the clicking is the startup winding being triggered on and off.
The motor seems to be deciding to drop back to startup.
Is this triggered by load (current draw) or speed?
Could the problem be my building wiring in some way?
DLB
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Location: Joshua Texas

Re: Motor clicks under load

Post by DLB »

Mrehder wrote: Tue Jul 12, 2022 9:34 am And further…
I connected a belt sander, putting the motor under load, and it labors, clicking in and out.

I think I understand now that the clicking is the startup winding being triggered on and off.
The motor seems to be deciding to drop back to startup.
Is this triggered by load (current draw) or speed?
Could the problem be my building wiring in some way?
I'm guessing none of us U.S. members have your exact motor because it is labeled 50 Hz. That said, every Mark 5/V conventional motor I've seen used a centrifugal start switch, so 100% based on motor speed. But there are other start circuits that work in other ways, for example the 60's version Mark VII does not use a centrifugal start switch. I strongly suspect yours works on motor speed, cannot confirm.

Your building wiring - Yes, it is possible. But it seems unlikely to me because power demands of the motor are greatest when it is starting. But 120V is standard in Canada, right? Are you connected to a 230V / 240V circuit? IIUC some circuits in Canada are 208V, that may complicate things because of phasing as well as the lower voltage. Can you confirm? (208V uses two phases of a three phase power source.)

- David
Mrehder
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Re: Motor clicks under load

Post by Mrehder »

The power supply is the same as in the USA. 240v, 60hz.
DLB
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Posts: 1984
Joined: Fri Nov 08, 2019 11:24 am
Location: Joshua Texas

Re: Motor clicks under load

Post by DLB »

Note that in an earlier post RFGuy listed several on-line resources. Here is one that may relate to your symptoms:

"When a 50Hz single phase motor is brought to 60Hz the start function can be upset because the motor reaches the centrifugal switch speed 20% earlier than normal. When it does, the starting torque of the motor is suddenly reduced. It could fail to speed up further and never reach normal running speed." https://www.engineering.com/story/chang ... 0-and-60hz

I was a bit skeptical of that, but at the same time it seems to relate to your symptoms. If the motor never reaches normal operating speed it will never produce normal operating power. If you have access to a tachometer you can check and monitor motor speed. If the clicking you hear is caused by a centrifugal start switch cycling between on and off then you are likely way below normal operating speed.

- David
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JPG
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Re: Motor clicks under load

Post by JPG »

Since the start switch trip point is speed related how is the timing relevant unless some delay factor is involved?
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DLB
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Joined: Fri Nov 08, 2019 11:24 am
Location: Joshua Texas

Re: Motor clicks under load

Post by DLB »

JPG wrote: Sun Jul 31, 2022 1:27 pm Since the start switch trip point is speed related how is the timing relevant unless some delay factor is involved?
I remain skeptical too. But the OP indicated that he believes the clicking under load emanates from 'the start winding being triggered on and off.' Suggesting, if true, that the motor is running at very low RPM. Somewhere near the off/on thresholds of the centrifugal switch.(?) And probably, I'm guessing, never reaching cruising RPM even when not clicking. In turn, caused by the motor not generating enough startup torque to reach normal operating range.(?) Thus, my thinking that a tachometer would be enlightening if readily available.

It got me thinking that the author's "...20% earlier than normal..." meant in RPM. If his 80% of running RPM is reasonable, then this motor's startup would switch out at ~2280 RPM because it is a 50 Hz motor. But that is only ~66% of the running RPM when running the motor on 60 Hz. Thus switching the start windings out at a point in startup when the main windings are still producing less torque (than a 60 Hz motor on 60 Hz would be producing at 2760 RPM). And not enough to overcome the load.(?)

More questions than answers, but a tach would answer most of them. (Claims the guy without a tach.)

- David
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