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raghun (Electrical) (OP)
19 Jan 08 22:36
I have Heat run test results for a motor. Can I  calculate Heating and Cooling Time constants from this data!
Thanks.
Helpful Member!  7anoter4 (Electrical)
24 Jan 08 4:52
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
raghun (Electrical) (OP)
24 Jan 08 5:05
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.
slavag (Electrical)
24 Jan 08 11:08
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
raghun (Electrical) (OP)
25 Jan 08 3:55
I do have SPAM Calculation tool (EXCEL) by ABB also. I will check REM manual. Thanks slavag.

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