Repulsion induction motor question

[SIDNEYP]

TL;DR

Motor spinning too fast?

Hello everyone,

I have an old Hobart A200 mixer that I've rebuilt and the problem is the agitator shaft is spinning twice the rated speed when the motor comes up to speed. It has a repulsive induction motor. Speed 1 starts at about the rated 60 rpm but spins at about 120 when at running speed. Forget 3d third speed. Way too dangerous. There are 4 black unmarked wires. It's wired for 120v (See attached). Is there any possible way I may have wired it incorrectly and is there a way to identify which wire is which? Or is it a mechanical problem? Thanks,

 

[Baluncore]

Welcome to PF.
Maybe you have found a way to connect the stator as a 2 pole stator rather than the 4 pole stator as it was before.
Did you rewind the motor, or just rearrange the connections?

 

[SIDNEYP]

It's still connected as 4 pole and the motor is not rewound. I replaced the original switch as it was shorting out and throwing sparks. I'm thinking maybe the wires are paired wrong at the switch.

 

[Baluncore]

Does the motor have movable brushes that can be positioned to control the speed?
How many brushes are there?
Could they have been reinstalled in the wrong position?

 

[SIDNEYP]

Yes, it has movable brushes and is set cc rotation (per manual). At the lowest rpm on speed 1, it starts at about 60 rpm. As I rotate clockwise slowly, the run rpm engages at 120 rpm. The further I turn it, the run rpm starts quicker but at the same 120 rpm.

 

[SIDNEYP]

My guess is that the motor is running on 2 poles only which may account for the higher speed. Also, when testing the mixer with bread dough, 2nd speed looses torque and is reduced to 1st speed rpm.

 

[Baluncore]

My guess is that the motor is running on 2 poles only which may account for the higher speed.

The problem is working out how to connect the 4 field wires, and how that could change the number of poles.

 

[Baluncore]

There is an interesting way of changing between two and four phase by connecting the brushes.
See the diagram. https://en.wikipedia.org/wiki/Repulsion_motor#Deri

Also; How is your field winding constructed? Is it wound on a slot stator, or does it have 2, or 4 pole pieces?