System and method for estimating motor temperature of a pitch system of a wind turbine

A pitch system for a wind turbine, the pitch system cornprising:

• a pitch drive motor comprising an armature and a shunt field winding;
• at least one sensor configured for monitoring an actual temperature of the shunt field winding during a normal operating period of the wind turbine;
• a converter communicatively coupled to the pitch dive motor so as to drive the armature;
• and,
• a pitch controller communicatively coupled to the at least one sensor, the pitch controller comprising at least one processor configured to perform the following operations:
• storing and updating the monitored temperatures and the monitored additional operating conditions of the shunt filed winding of the motor for the normal operating period;
• storing updated monitored parameters of an additional operatin condition of the motor during the normal operating period;
• determining a relationship between the monitored temperatures and the monitored parameters of the additional operating conditions of the motor for the normal operating period;
• and,
• upon failure of the sensor to operate, determining an estimated temperature of the motor based on the relationship determined during the normal operating period based on the updated monitored temperatures and updated monitored parameters preceding the failure.