Split phase Motor

[fireryan]

I have a old split phase motor with an old drum switch where all the wiring diagrams are gone. It’s a 5hp Baldor single phase motor. The motor is taking 220 volts directly off a 2 pole breaker that I assume is going to the main windings. Then there is a wire off 1 of the phases of the 2 pole breaker that goes to a drum switch which I assume is switching leads 5 and 8 on the motor and then 3 other wire that come off the drum switch that go to the motor as well. Anybody have an idea where I can find a wiring diagram for this? I’ve been striking out everywhere I look

 

[ptonsparky]

I have a old split phase motor with an old drum switch where all the wiring diagrams are gone. It’s a 5hp Baldor single phase motor. The motor is taking 220 volts directly off a 2 pole breaker that I assume is going to the main windings. Then there is a wire off 1 of the phases of the 2 pole breaker that goes to a drum switch which I assume is switching leads 5 and 8 on the motor and then 3 other wire that come off the drum switch that go to the motor as well. Anybody have an idea where I can find a wiring diagram for this? I’ve been striking out everywhere I look

An old AB or CH catalog for manual motor controls.

 

[Russs57]

Depends on the motor, how many leads, and what you want the switch to do.

Typical forward/reverse switching would be:
A phase to T1 and B phase to T4 (those always stay like that)
A phase to T8 and B phase to T5 for forward
A phase to T5 and B phase to T8 for reverse.

 

[garbo]

Depends on the motor, how many leads, and what you want the switch to do.

Typical forward/reverse switching would be:
A phase to T1 and B phase to T4 (those always stay like that)
A phase to T8 and B phase to T5 for forward
A phase to T5 and B phase to T8 for reverse.

Have not touched a drum switch in about 40 years but seems right. We would wire in the one set of contacts that never reversed to the stop circuit. Had too many operators moving drum switch fast from say forward speed to reverse causing blown fusses. Asked them how often while driving 60 MPH do they throw their car transmission into reverse. We used to mount drum switch on cover if large Hoffman enclosures

 

[gar]

220209-0654 EST

See

Split-Phase Induction Motor – Operation and Characteristics

Split Phase Induction Motor Operation and Characteristics - A split-phase induction motor is a type of single-phase induction motor in which the stator is provided with a starting or auxiliary winding (S) and a main or running winding (M). The starting winding is displaced by 90° from the main...

www.tutorialspoint.com

for a discussion of how a split phase motor works.

A true pure single phase induction motor has an oscillating magnetic field in only one direction in space. This goes from zero to a maximum positive value, then reverses, and goes back to zero, and reverses to a maximum in the opposite direction ( negative ), and then back to zero. This kind of magnetic field oscillation will not start a motor rotating. You could put a pulley on the motor and wrap a rope around the pulley and use this to manually start a pure single phase motor.

However, that is not a practical method. Thus, if instead you can create a magnetic field that rotates in space, then you can have an auto start means. There are various ways to do this.

The so called "split phase motor" is one way.

By adding a second winding to the motor, positioning it 90 degrees from the main winding, and feeding a current shifted in phase from the main winding you can create a somewhat rotating magnetic field that will start the motor. This start winding is dropped out when the motor reaches a sufficient speed.

Once you have a true single phase motor up to near full speed, then the single phase pulsating input can keep the motor running near synchronous speed. This is because off the inertia of the system. It operates much like a swing where you pulse energy into th swing in sync with the swing motion.

One bad characteristic of a single phase motor is that puts torque pulses into the load.

Not mentioned in the referenced discussion is that direction of rotation is determined by the relative phasing of the start and run windings.

.

 

[kwired]

I have a old split phase motor with an old drum switch where all the wiring diagrams are gone. It’s a 5hp Baldor single phase motor. The motor is taking 220 volts directly off a 2 pole breaker that I assume is going to the main windings. Then there is a wire off 1 of the phases of the 2 pole breaker that goes to a drum switch which I assume is switching leads 5 and 8 on the motor and then 3 other wire that come off the drum switch that go to the motor as well. Anybody have an idea where I can find a wiring diagram for this? I’ve been striking out everywhere I look

You described what happens pretty well. You just need to determine which two poles of drum switch are being reversed. One pole switches straight through for either direction the other two poles reverse polarity when you switch direction. You must break one of the main winding leads (1 or 4) when in off position or main winding will continue to draw current The other two poles reverse polarity of aux winding (5 and 8) depending on which way the switch is operated.

On a split phase motor you must wait for load to come to stop or near stop before reversing. If it hasn't slowed enough to close the centrifugal start winding switch before switching other direction it will continue to run same direction it was before.