Motor protection cooling time constants?

[rmendozaing]

In GE Multilin motor protection relays is possible to set values for cooling time constants (running and stopped).
Anyone knows typical values for these constants for different HP motors?
It is clear that these values are affected if the motor haves external forced cooling (big motors).
I did search internet, but I didn't find any reference or recommendation.
Thanks in advance.

 

[Skogsgurra]

The time constant varies a lot. A "standard" value used is often 15 minutes. But there are large totally enclosed self-cooled motors that have time constants between 1 and 2 hours and there are motors with forced ventilation that have time constant down to a few minutes.

Most motor manufacturers have these data listed in their motor data sheets. Search Rockwell/AB, Siemens and ABB sites.

Gunnar Englund

http://www.gke.org