Repulsion induction motor question

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Discussion Overview

The discussion revolves around troubleshooting a repulsion induction motor in a Hobart A200 mixer, specifically addressing issues related to the motor running at an unexpectedly high speed. Participants explore potential wiring errors, mechanical problems, and the configuration of the motor's components.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant suggests that the motor may be incorrectly connected as a 2 pole stator instead of a 4 pole stator.
  • Another participant considers the possibility of the wires being paired incorrectly at the switch after a replacement.
  • A question is raised about the presence and positioning of movable brushes, which could affect the motor's speed control.
  • One participant notes that the motor starts at about 60 rpm but reaches 120 rpm at running speed, indicating a potential issue with the pole configuration.
  • Another participant mentions that the motor's performance decreases under load, suggesting a loss of torque at higher speeds.
  • There is a mention of a method to change between two and four phases by adjusting the brush connections, indicating a possible area for further investigation.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the cause of the high speed, with no consensus on whether the issue lies in wiring, mechanical configuration, or the motor's design.

Contextual Notes

Participants have not fully resolved the implications of the wiring configuration or the mechanical setup of the motor, leaving open questions about the specific connections and their effects on performance.

SIDNEYP
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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,
 

Attachments

  • Hobart A200.jpeg
    Hobart A200.jpeg
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Engineering news on Phys.org
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?
 
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.
 
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?
 
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.
 
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.
 
SIDNEYP said:
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.
 
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?
 

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