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Electric motor running backwards Answered

I have an electric motor on a large Hobart vertical mixer 80 quart.

I had the brushes replaced and put it back together

It now runs in reverse

It is a single phase motor with four brushes that have no power to them there is no capacitor either

It is an old style motor

Any help would be greatly appreciated even what type of motor this is

Thanks David

9 Replies

user
rickharris (author)2018-02-14

This sounds like a split phase motor with 2 windings:
From Wikipedia https://en.wikipedia.org/wiki/AC_motor#Split-phase_motor

"Another common single-phase AC motor is the split-phase induction motor,[18] commonly used in major appliances such as air conditioners and clothes dryers. Compared to the shaded pole motor, these motors provide much greater starting torque.

A split-phase motor has a secondary startup winding that is 90 electrical degrees to the main winding, always centered directly between the poles of the main winding, and connected to the main winding by a set of electrical contacts. The coils of this winding are wound with fewer turns of smaller wire than the main winding, so it has a lower inductance and higher resistance. The position of the winding creates a small phase shift between the flux of the main winding and the flux of the starting winding, causing the rotor to rotate. When the speed of the motor is sufficient to overcome the inertia of the load, the contacts are opened automatically by a centrifugal switch or electric relay. The direction of rotation is determined by the connection between the main winding and the start circuit. In applications where the motor requires a fixed rotation, one end of the start circuit is permanently connected to the main winding, with the contacts making the connection at the other end."

Hoe to reverse
https://woodgears.ca/motors/reversing.html
http://forums.mikeholt.com/showthread.php?t=141847

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user
-max- (author)2018-02-13

4 brushes? And I suppose that they are connected in pairs too? I think what you have is known as a *repulsion* motor. Took me ages to figure this out when I was working on getting an old metal lathe running. The one on mine disengages the brushes when it reaches synchronous speed since it's a repulsion-start induction-run motor.

I think to reverse the speed you simply rotate the bit that holds the brushes 90 degrees, but it's been awhile so don't take my word for it. Google is your friend! :)

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user
steveastrouk (author)2018-02-12

Very strange ! There are instructions online of how to change the direction of a UNIVERSAL motor. - easier to find than for me to explain.

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user

The motor has a plate with four brushes mounted on it which goes over the motor shaft it is not attached to any electricity
I took it off and had the brushes replaced and then put back together
It now runs in reverse
it is a single phase motor no capacitator
the only thing I can see different is that one of the brushes had one wire on it instead of two these brush wires are just attached to the brushes and just screw into the plate that goes over the motor shaft
any suggestions would be appreciated

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user
-max- (author)David Ferguson2018-02-13

4 brushes? And I suppose that they are connected in pairs too? I think what you have is known as a *repulsion* motor. Took me ages to figure this out when I was working on getting an old metal lathe running. The one on mine disengages the brushes when it reaches synchronous speed since it's a repulsion-start induction-run motor.

I think to reverse the speed you simply rotate the bit that holds the brushes 90 degrees, but it's been awhile so don't take my word for it. Google is your friend! :)

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user
rickharris (author)2018-02-13

The motor can be reversed, You have probable swapped 2 connections when changing the brushes.

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user
Josehf Murchison (author)2018-02-13

The brushes were switched.

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user
iceng (author)2018-02-12

if it has field windings exchange the wires of every coil..

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user
David Ferguson (author)iceng2018-02-12

The motor has a plate with four brushes mounted on it which goes over the motor shaft it is not attached to any electricity
I took it off and had the brushes replaced and then put back together
It now runs in reverse
it is a single phase motor no capacitator
the only thing I can see different is that one of the brushes had one wire on it instead of two these brush wires are just attached to the brushes and just screw into the plate that goes over the motor shaft
any suggestions would be appreciated

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