Motor Thermal time constant
Motor Thermal time constant
(OP)
Dear all. On site we have one 6.3 kV motr, 1090kW. This motor is vertical mounted, drivinf one main cooling water pump of our power station. The pump had a very big failure on the bearings and the motor was left running for 20 minutes with currents higher than nominal. the motor has SIPROTEC protection relay 7SJ63. The thrmal time constant is set 80 minutes but this is not the value of the motor manufacturer. I think to decrease it to 40 min at least. Is that a good idea?





RE: Motor Thermal time constant
If you think the relay should have tripped on overload, you need to first verify the Full Load Amp setting and the minimum pickup setting of the relay (which I'm not really familiar with)
Motor stator RTDs might be a better indicator of *long-term* overloading of the motor than the thermal model, although they will be too slow to help with short term locked-rotor type heating.
RE: Motor Thermal time constant
RE: Motor Thermal time constant
RE: Motor Thermal time constant
If you want to tweak the time constant or overload setting based on your experience, that's your perogative. Just consider possible possible scenario's that create temporary where you don't want to trip and make sure you set high enough/long enough to avoid tripping. For example if a sister pump trips, does this pump run at overload until the sister is recovered?
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor Thermal time constant
If you want to tweak the time constant or overload setting based on your experience, that's your perogative. Just consider possible scenario's that create temporary overload where you don't want to trip and make sure you set high enough/long enough to avoid tripping. For example if a sister pump trips, does this pump run at overload until the sister is recovered?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor Thermal time constant
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor Thermal time constant