Can this motor be repaired?

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
Hi,
The attached pictures shown Single Phase Induction Motor taken from a Lathe machine, the reason is lost power.
The motor can turn in empty, no power; the capacitor measured the reading decrease to 0 and then increase by a digital multimeter.
Can it be repaired?
Thanks
Adam
motor2.jpgmotor3.jpg
 

Delta Prime

Joined Nov 15, 2019
1,022
hello there! :) Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. If the motor is less than 1/8 HP, it is almost always replaced.
Begin to check the bearings of the motor.
Perform a check of the bearings.
Next, push and pull the shaft in and out of the frame
Check the windings for short circuiting to the frame.
Use an ohmmeter to check resistance value.
Check that the windings are not open or blown.
Check the start or run capacitor used for starting or running some motors, if equipped.
Check the rear bell housing of the motor.
Check the fan
could you take another picture of the specification plate, so I can show you how to calculate the horsepower
 
Last edited:

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
hello there! :) Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. If the motor is less than 1/8 HP, it is almost always replaced.
Begin to check the bearings of the motor.
Perform a check of the bearings.
Next, push and pull the shaft in and out of the frame
Check the windings for short circuiting to the frame.
Use an ohmmeter to check resistance value.
Check that the windings are not open or blown.
Check the start or run capacitor used for starting or running some motors, if equipped.
Check the rear bell housing of the motor.
Check the fan
Thank you.

1. More pictures here.
2. Did't see any thing strange of centrifugal switch in second picture, how to check it?
3. Is the third picture a thermal switch? how to check it?
4. The coil is not short to body.
5. Measured the two red terminals of the coil by an ohmmeter and read 1.3 ohm see picture 4th.
6. I plan to shift another capacitor to test the motor when I got the number.
Best.

Nameplate.jpgcentrifugal switch.jpgthermal switch.jpgconnector.jpg
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
23,123
A single phase motor with no power (low current flow) indicates an open rotor, but I have not seen this in decades when copper bars were common.
Otherwise it is very much like a short across the line with no rotation.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
A single phase motor with no power (low current flow) indicates an open rotor, but I have not seen this in decades when copper bars were common.
Otherwise it is very much like a short across the line with no rotation.
Thanks.
The motor is a 0.75kw, and used a capacitor:
300uf-125v? is this number too large?
may I use a 30uf 450V instead of?
And how to test the motor's Torque without put back to machine?
Best.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
23,123
That appears to be a start capacitor which is generally a large value, was this the original?
Normally if the start winding/cap is faulty, a spin of the shaft at the same time as applying power would start the motor.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
That appears to be a start capacitor which is generally a large value, was this the original?
Normally if the start winding/cap is faulty, a spin of the shaft at the same time as applying power would start the motor.
Thanks.
It is a original one, measured seems OK, but no reason else found.
The centrifugal switch is fine at my checking.
 

MaxHeadRoom

Joined Jul 18, 2013
23,123
You describe the symptoms as "loss of power", have you measured the current?
If the motor is not rotating or low RPM with zero torque & low current with full voltage, it is not the capacitor or start switch
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
You describe the symptoms as "loss of power", have you measured the current?
If the motor is not rotating or low RPM with zero torque & low current with full voltage, it is not the capacitor or start switch
Thanks.
I didn't measure the current yet, I'll do it.
BTW. how to measure the large current? I just have a multimeter that can read max. 10A.
 
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Thread Starter

LAOADAM

Joined Nov 21, 2018
563
There is 4 wires block as picture shown, how to wiring it to 110v for test?
The two red is main coil, and the blue goes to capacitor.
Thanks
connector.jpg
 

MaxHeadRoom

Joined Jul 18, 2013
23,123
You connect it up ion the normal way.
I would guess that each coloured pairs are start and run winding, the one with the lowest resistance is the run, the higher, the (blue) start winding
Have you ever had the rotor out to see if in fact it has copper bars?
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
You connect it up ion the normal way.
I would guess that each coloured pairs are start and run winding, the one with the lowest resistance is the run, the higher, the (blue) start winding
Have you ever had the rotor out to see if in fact it has copper bars?
Thanks.
I'll test it.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
hello there! :) Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. If the motor is less than 1/8 HP, it is almost always replaced.
Begin to check the bearings of the motor.
Perform a check of the bearings.
Next, push and pull the shaft in and out of the frame
Check the windings for short circuiting to the frame.
Use an ohmmeter to check resistance value.
Check that the windings are not open or blown.
Check the start or run capacitor used for starting or running some motors, if equipped.
Check the rear bell housing of the motor.
Check the fan
could you take another picture of the specification plate, so I can show you how to calculate the horsepower
Thanks.
Here is the report by my test:
1. the both bearing are fine;
2. the windings no short to the body;
3. there is no traces of wear or broken any where inside;
4. the coil read 1.3 ohm by a digit multimeter;
5. Checked the windings as #4 seems no open or blown;
6. Checked the starting capacitor used to start another one motor OK;
7. Checked the rear bell housing of the motor and the fan all OK;
8. Used a 25uf 450V capacitor try to start the motor failed but noise buzzing.
attached some more pictures may be coil burnt?

fan end2.jpgshaft end.jpg
 

anniel747

Joined Oct 18, 2020
1,122
Thanks.
Here is the report by my test:
1. the both bearing are fine;
2. the windings no short to the body;
3. there is no traces of wear or broken any where inside;
4. the coil read 1.3 ohm by a digit multimeter;
5. Checked the windings as #4 seems no open or blown;
6. Checked the starting capacitor used to start another one motor OK;
7. Checked the rear bell housing of the motor and the fan all OK;
8. Used a 25uf 450V capacitor try to start the motor failed but noise buzzing.
attached some more pictures may be coil burnt?

View attachment 240651View attachment 240652
Looks like you have a burnt switch and winding.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
Time to see your local transformer/motor specialist.
Thanks.
Do you mean 'the centrifugal switch' ? I don't know the suitable method to check it, the weights, the springs of the centrifugal switch all function well by manually moving, the switch reed same.
Any way to check the coil burnt or not?
Thanks
 
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