Hi,

I am a hardware design engineer and designed a BLDC motor controller (sensorless) using IPM. During testing, I faced an issue such that when conducting Locked Rotor Test, the method is as follows:
1. First the motor will rotate at no load
2. I have to fix the blades while the motor is running
So, here, while fixing the blades, the motor faces lock rotor condition. Then after 30 sec, the motor should operate normally.
During test conduction, we observed voltage spike during lock condition as the motor tries to rotate in the input side and output phase side. Why it is happening? Can anyone suggest a solution for reducing this spike?

 

You are trying to lock the rotor using the program or manually holding the motor, how can you fix blades while motor is running? It may most probably the back emf generated by the motor when you suddenly stop supplying current to the motor.

 

Can you please explain your "fixing the blade" scenario. From your text it seems that the fan blades are physically locked and the motor drive circuit is trying to drive current into the phases. Is this the case? Please give us more information.