reversing rotation on electric motors.

Mike(NEOhio) · Sep 15, 2020

I scrapped the motor from my cummins-mack drill press, mice nested in it and chewed the field windings. Put the motor from the C-M bandsaw on but it's the opposite
rotation. 3/4 Hp four pole capacitor. Can the direction be reversed?

dr sportster · Sep 15, 2020

It depends if the motor lets you have long enough leads to make the switch. Some are not reversable.

dr sportster · Sep 15, 2020

Reverse polarity on the start windings . If you can get the leads

Russ from MN · Sep 15, 2020

Most electric motors can be easily revered, many have instructions inside the terminal cover. The one exception is water pump motors, if they were to start in the CC direction it might unscrew the impeller, as many just screw on. But, if your determined enough, it can be done. I pulled a 1 hp pump motor out of the dumpster at work once, but it ran the wrong direction for my air compressor. I had an electrician look at it, he said "no, it can't be reversed" I mentioned that to a fellow millwright who was an exceptional thinker, and he said, "why don't you turn the stator around"! So, I did that, and it's been running my air compressor for 25 years!

4520BW · Sep 15, 2020

Most single phase you just switch the wires that go to #5 and #8 wire.

Dusty MI · Sep 15, 2020

Look at the inside of the terminal cover, usually theres a wiring diagram there.

Red Dave · Sep 15, 2020

"Look at the inside of the terminal cover, usually theres a wiring diagram there."

Correct.

I've also made my drill press reversible and there was no wiring diagram under the cover.

I googled the connections diagram for the make and model of the motor. It showed the connections for either rotation. A DPDT switch later and now my drill press is reversible. Just don't throw that switch while the motor is running, it's really hard on the motor.

Mike(NEOhio) · Sep 15, 2020

OK, this is one of those cheap chinese motors. I'll look into it tomorrow.

wore out · Sep 15, 2020

(quoted from post at 10:47:53 09/15/20) "Look at the inside of the terminal cover, usually theres a wiring diagram there."

Correct.

I've also made my drill press reversible and there was no wiring diagram under the cover.

I googled the connections diagram for the make and model of the motor. It showed the connections for either rotation. A DPDT switch later and now my drill press is reversible. Just don't throw that switch while the motor is running, it's really hard on the motor.

"Just don't throw that switch while the motor is running, it's really hard on the motor."

Who told you that?

Reality is that if you quickly flip the reversing switch and the motor stays above the speed the centrifugal start switch kicks in NOTHING will happen, no reverse, no motor destruction, NOTHING, it will not reverse.

If the reversing switch has a "center off", and you dally a little 'til the motor speed has coasted down enough to kick in the start windings it will simply reverse without any major destruction.

If the motor is on a lathe reversing just before a stop MAY loosen or completely spin off the chuck, still no motor destruction, though!

Stephen Newell · Sep 16, 2020

Not all motors are reversible. There should be information on the motor on a plate which tells how to reverse the motor if it's the kind.

John T · Sep 16, 2020

A typical single phase split phase motor uses a separate "start" winding which gets it spinning in a certain direction and at X RPM a centrifugal switch opens (is closed initially) and the "run" winding alone continues to operate. To reverse direction the leads on that "start" winding get reversed. One problem is the centrifugal switch contacts get burned pitted carboned and resistive or maybe they stick closed.

John T

Red Dave · Sep 16, 2020

Well then please, by all means, reverse your spinning motors any time you want to.

Let mine alone, thank you.

wore out · Sep 16, 2020

(quoted from post at 06:23:35 09/16/20) Well then please, by all means, reverse your spinning motors any time you want to.

Let mine alone, thank you.

You missed my point completely.

A common motor with a centrifugal start switch and a simple reversing switch WILL NOT reverse if the switch is flipped when the motor is "at speed".

So "reverse your spinning motors any time you want to" does not apply, as it's impossible.

On the other hand, there are specialty motors available that are called "instant reversing" and WILL reverse instantly, "at speed" and survive such treatment day in and day out.

miangus · Sep 16, 2020

The motor on my drill press, a line shaft conversion can be reversed by loosening a bolt and adjusting the brush position. The Patent date is 1921. Many of my friends have laughed at the old flat belt driven antique. The laughing usually stopped when they needed a 3/4' hole drilled in 3/4 inch plate.

John T · Sep 16, 2020

That brush type Repulsion motor IS NOT the same as an Induction motor so reversing is a different process. Brush repulsion motors have good starting torque. Years back I saw some Repulsion Start Induction Run and wow those would start a ferris wheel lol

John T

reversing rotation on electric motors.

Mike(NEOhio)

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dr sportster

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dr sportster

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Russ from MN

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4520BW

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Dusty MI

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Red Dave

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Mike(NEOhio)

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wore out

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Stephen Newell

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John T

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