Most important power electronics in powering PM motor
PM (Permanent Magnet) motor, which has a flux that cannot be turned off. So, you should make sure your power electronics can handle the max back EMF corresponding to max speed of the motor. If you require flux weakening at top speed to reduce the Vemf, you should make sure you can handle that full Vemf if you lose that direct axis current.
The second item is to have a "per unit inductance machine", meaning that the flux linkage and inductance are designed such that if the machine shorted to DC neg reference, the current would not exceed rating of your transistors.
(Isc=V/Z~Vemf/w*L=(w*Lambda)/(w*L)=Lambda/L)---> Isc = Lambda/L
Last, with a PM machine, if you are above base speed (flux weakening), and have a fault (say resolver fault), so you put the transistors all open, you will regenerate current onto your bus (since Vemf > Vbus) until speed falls below base speed (there will be a braking torque during this time to help slow, but depending on inertia of system, still could be a long time.) If your bus cannot dissipate this current, Vbus rises and things get bad.
The second item is to have a "per unit inductance machine", meaning that the flux linkage and inductance are designed such that if the machine shorted to DC neg reference, the current would not exceed rating of your transistors.
(Isc=V/Z~Vemf/w*L=(w*Lambda)/(w*L)=Lambda/L)---> Isc = Lambda/L
Last, with a PM machine, if you are above base speed (flux weakening), and have a fault (say resolver fault), so you put the transistors all open, you will regenerate current onto your bus (since Vemf > Vbus) until speed falls below base speed (there will be a braking torque during this time to help slow, but depending on inertia of system, still could be a long time.) If your bus cannot dissipate this current, Vbus rises and things get bad.
<- - Make a Comment - ->
Servo Motor & Drives
buy@servomotor.co
