Repulsion induction motor question

In summary, the Hobart A200 mixer has a repulsive induction motor that is spinning twice the rated speed. The problem is that the agitator shaft is spinning at a high speed and it is dangerous to operate the mixer at this speed. There are 4 black unmarked wires that are connected to the mixer, but it is unclear how they are connected. The mixer has 2 and 4 pole pieces that are designed to change between two and four phase. The problem is that the field winding is not properly constructed and it is not clear how the wires are connected.
  • #1
SIDNEYP
4
0
TL;DR Summary
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,
 

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  • #2
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?
 
  • #3
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.
 
  • #4
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?
 
  • #5
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.
 
  • #6
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.
 
  • #7
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.
 
  • #8
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?
 

1. What is a repulsion induction motor?

A repulsion induction motor is a type of electric motor that uses both repulsion and induction principles to operate. It is typically used in applications where high starting torque and variable speed control are required.

2. How does a repulsion induction motor work?

A repulsion induction motor has a stator and rotor, similar to other types of motors. The stator has a set of stationary windings, while the rotor has a set of rotating windings. When electricity is supplied to the motor, the stationary windings create a magnetic field that interacts with the rotating windings, causing the rotor to turn.

3. What are the advantages of a repulsion induction motor?

Repulsion induction motors have high starting torque, making them suitable for applications that require heavy loads to be started. They also have variable speed control, allowing for more precise control over the motor's speed. Additionally, they are relatively simple in design and therefore, cost-effective.

4. What are the disadvantages of a repulsion induction motor?

One of the main disadvantages of a repulsion induction motor is its high maintenance requirements. The brushes and commutator in the rotor need to be regularly inspected and replaced, which can be time-consuming and costly. They also have lower efficiency compared to other types of motors.

5. Where are repulsion induction motors commonly used?

Repulsion induction motors are commonly used in industrial applications, such as cranes, hoists, and elevators, where high starting torque and variable speed control are necessary. They are also used in household appliances like washing machines and vacuum cleaners.

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