winding resistance test for 3 phased AC Dahlander motor

[Buhl]

Hi

Im not an electrical engineer but have somehow got involved in tests of ac motors.
Could someone tell me if there is a standard for the below measurements to compare motors e.g. from different suppliers.
And also what the purpose is - what can these measurements tell about the motor and how can it be used to compare motors.

Winding resistance is measured on the "cold" motor and the surface temperature is measured.
The motor is then run (in this case driving an impellor) for 1-2 hours until temperature is stabil.
The surface temperature is noted.
Then power is cut and stopwatch is started.
You wait for 10-20 seconds until the shaft has stopped moving completely.
The winding resistance is measured and the time of the measurement is noted
This is repeated with 5-10 sec. between measurements until you have 5-10 measurements.

The output of the tests is:
Delta temperature
Resistance at time 0 (the excat time of power cut)
Winding mean temperature

Best Regards
Buhl

 

[electricpete]

And also what the purpose is - what can these measurements tell about the motor and how can it be used to compare motors.

These measurements are used to estimate what the winding tempearture was just before you shut down the machine.

Also if you look for difference in high-precision resistance measurement among phases (just requires one set of 3 measurements, not the elaborate group of tests you mentioned), you might possibly find a motor problem.


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(2B)+(2B)' ?

 

[Buhl]

Thank you - but if i order the motor with a PT100 sensor build inside then i dont need these tests ?

 

[electricpete]

I would not bother with any resistance measurements other than single set of three precision readings. Everything else is to determine temperature, which you already know.

=====================================
(2B)+(2B)' ?

 

[Buhl]

I know the temperature only if i order the motors with bould in temp. sensor.
Otherwise i have to measure outside on the motor surface with a laser thermometer or maybe use thermal imaging.
You suggest to measure the 3 windings with high precision instrument and the values should be the same with some tolerance?