Single Phase Motor Repair-Controller issue?

Thread Starter

Ppaper Clip

Joined Apr 18, 2019
6
Hello Everyone,
This is my first post here and so don't know if I am asking in the right place.

I am also new to EE/circuits/motor repair and have elementary understanding at best. (however I take safety very seriously)

Below are pictures of a single phase motor with two capacitors that was removed from a Taylor soft serve yogurt machine.
These motors breakdown every two years or so and are costly to repair. The shop manager let me take the motor home so that I could learn from and possibly fix.

From my previous research I know that I am having a controller issue. There were also two free floating metallic pieces that were broken/burned (did they connect to the controller and act as resistors?)

If anyone could help me with repairing this motor, that would be awesome. Or at least point me in the right direction. I am eager to learn and thanks for reading my post.

Alan
 

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MaxHeadRoom

Joined Jul 18, 2013
23,912
Appears the centrifugal switch failed.
Also maybe a flash over at failure burnt/melted the aluminum pieces.
One thing I have done in the past to preserve a centrifugal switch is to use the switch for a Triac gate, and use the Triac to switch the start winding on/off.
The Triac can be mounted externally if necessary.
The other option is do away with the internal Centrifugal SW altogether and fit an external current relay version.
Max.
 

Thread Starter

Ppaper Clip

Joined Apr 18, 2019
6
Thank you sir for your reply. I am not sure i am capable of using a Triac as I dont know what that is. I can however replace the centrifugal switch. Could I use any centrifugal switch?

I am not sure what those aluminum pieces were used for. Do you have any idea what those could be? I dont have a reference motor to work with.

Thank You!
 

MaxHeadRoom

Joined Jul 18, 2013
23,912
Not quite sure what the aluminum pieces do? you would need to see them on a good motor to get a better idea.
If only interested in rebuilding them, you would need to get the replacement centrifugal switch, I am guess the motor is Chinese in origin?
The other thing to check when replacing a motor is to see if the replacement has Chinese origin start & run capacitors, if so, it may pay to replace them with N.A. quality CDE etc. this also could act as preventative maintenance.
Chinese motors are famous for early cap failure.
Do you have a new motor you can inspect?
Max.
 

Thread Starter

Ppaper Clip

Joined Apr 18, 2019
6
1.) I wish i had a new motor to inspect but the good motor is in the yogurt machine doing its thing. I don't know if it is Chinese-origin but printed on the side are Mexico labels. However it's most likely Chinese and assembled in Mexico.

2.) I am just interested in replacing the Centrifugal Switch and hopefully this will complete the repair.

3.) I included a picture of the diagram on the motor label. Will this help me choose the right switch i need?

4.) I will disassemble the capacitor and post picture to see if it is Chinese capacitor when I get the chance.

5.) What is NA quality CDE acronym stand for (North America and CDE???)
 

MaxHeadRoom

Joined Jul 18, 2013
23,912
I may be wrong, they may be Wisconsin source parts and assembled in Mexico, I see the bearings are Chinese, however.
N.A. = North America. CDE is the manufacturer.
Unfortunately you most likely need the same switch as they are usually individual to the motor design, maybe shoot a email to Marathon and inquire about a replacement switch source.
Max.
 

LesJones

Joined Jan 8, 2017
3,570
I suspect that the aluminium pieces are bob weights on the centrifugal switch. I think they would be mounted on the rotating part and held together by springs. When the motor reached a certain speed the centrifugal force would be enough to overcome the strength of the springs so the weights would move and via some kind of linkage operate the switch contacts. I have seen two other methods of disconnecting the start winding. One is a relay whose coil is in series with the run winding. When the motor is up to speed the run winding will drop to a value that will not hold the relay contacts closed. The other method is a positive temperature coefficient thermistor in series with the start winding. The thermistor method would not work if the motor was not stopped for long enough for the thermistor to cool down between starts.

Les.
 

shortbus

Joined Sep 30, 2009
8,957

MaxHeadRoom

Joined Jul 18, 2013
23,912
The current relay that I also mentioned in #2 often has to be selected for individual start winding's as they are not always one-size-fits-all, unfortunately.
Max.
 

Thread Starter

Ppaper Clip

Joined Apr 18, 2019
6
I am reaching out to service reps but no answer yet. Cant seem to find the replacement parts. But I think LesJones is right about the mechanism, especially since I have another broken motor of the same type with the same problem.
 

LesJones

Joined Jan 8, 2017
3,570
Hi SB,
Yes, that is the method I was suggesting. I have seen it used on fridge compressors. But as Max says the relay must be designed to match the starting and run currents of the motor.

Les.
 

MaxHeadRoom

Joined Jul 18, 2013
23,912
Yes I agree it looks like part of the centrifugal switch, doesn't appear to be a good/simple design compared to the run of the mill type.
It might certainly be worth looking into why the premature failure, if it looks like it could be due to contact failure, the Triac idea should certainly extend the life.
The contacts just switch the minute gate current only.
Max.
 
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