Setting up Electronic Thermal Motor Protection (ETH) on a VFD

Setting up Electronic Thermal Motor Protection (ETH) on a VFD

Electronic Thermal Motor Protection (ETH) is a protective function which protects the motor based on the programmed cooling characteristics of the motor. The VFD can be set to trip at a programmed level to protect the motor. This is primarily based on motor speed, motor current, and the cooling type of the motor.

Programming

The below settings are required for ETH. 
Note that setup on a VFD with an LCD keypad you simply be in the "PRT" parameters group instead of "Pr"


Self Cooled motors are ones which have the cooling fan attached to the shaft.

Forced Cooled are those which have a separately powered cooling fan. 


Operation

Referring to the below table, you can see that changing Pr.41 effects the speed at which the motor is allowed to slow down to before potentially tripping on ETH. This is because standard self cooled motors cannot adequately cool themselves when operating at lower RPM.