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# Motor heating and cooling time constants - Heat run test

## Motor heating and cooling time constants - Heat run test

(OP)
I have Heat run test results for a motor. Can I  calculate Heating and Cooling Time constants from this data!
Thanks.

### RE: Motor heating and cooling time constants - Heat run test

Hi Raghun,
According to Rudolf Richter Electrical Machine vol I
[Erster Band-zweite verbesserte Auflage Basel 1951]
The electric motor heating equation is as follows:
?=Theta
Theta=ThetaMax*(1-exp^(-t/T))+Thetao*(exp^(-t/T))
where Theta is the actual temperature ThetaMax is the maximum temperature reached by a machine
and Thetao is initial temperature.
T is the heating constant and t is the heating time.
So T=t/Ln(ThetaMax-Thetao)/(ThetaMax-Theta)
R.Richter took the same constant as cooling constant.
Theta=Thetai*(exp^(-t/Tcooling))
Where Thetai is the initial cooling temperature
According to Siemens Handbook for Electrical Engineer chpt.7.5.3 Tcooling=(1.4 -2) *Theating
Best regards

### RE: Motor heating and cooling time constants - Heat run test

(OP)
Thanks 7anoter4 for the info.
The cooling constant can be 3-6 times the heating constant as per the literature of ABB make SPAM motor protection relay. This is also seen in the data sheets of HV motors many times.

### RE: Motor heating and cooling time constants - Heat run test

Hi Raghun.
I rcommend to you check ABB make REM610, more information then SPAM150.
Are you have for SPAM application example too, or only manual?
Regards.
Slava

### RE: Motor heating and cooling time constants - Heat run test

(OP)
I do have SPAM Calculation tool (EXCEL) by ABB also. I will check REM manual. Thanks slavag.

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