EddyWirbelstrom
Electrical
- Feb 17, 2002
- 214
What is the max permissible temperature ( trip temp ) an F motor insulation can withstand for a short time before motor trip ?
I've read in Sprecher & Schuh documentation that motor F insulation can withstand a short-time temperature of approximately 250°C before motor trip.
F insulation continuous operating temp = 155°C - 10°C hot spot allowance = 145°C.
The settings for the ABB REF542plus motor protection relays includes the motor heating time-constant which can be determined by :-
Heating Time-Constant ( Tor ) = Motor Permissible Locked Rotor time from Cold / ( nat log ( motor LRC^2 / ( motor LRC^2 - k^2 ))).
Where LRC = motor Locked Rotor Current ( starting Current )
Where k = overload factor = (( Trip Temp - Amb Temp ) / ( ( Rated Temp - Amb Temp ) )^0.5
I've read in Sprecher & Schuh documentation that motor F insulation can withstand a short-time temperature of approximately 250°C before motor trip.
F insulation continuous operating temp = 155°C - 10°C hot spot allowance = 145°C.
The settings for the ABB REF542plus motor protection relays includes the motor heating time-constant which can be determined by :-
Heating Time-Constant ( Tor ) = Motor Permissible Locked Rotor time from Cold / ( nat log ( motor LRC^2 / ( motor LRC^2 - k^2 ))).
Where LRC = motor Locked Rotor Current ( starting Current )
Where k = overload factor = (( Trip Temp - Amb Temp ) / ( ( Rated Temp - Amb Temp ) )^0.5
