Possible errors in measurement of air-gap torque pulsations of induction motors

Measurements based on the accurately obtained air gap flux data using either the search-coil or the Hall-effect approach are not error proof. This is because even the unbalanced leakage effects can be reduced to a minimal value by measuring the air-gap flux at the tip of the slots. The magnetic paths of different axes may not be balanced at any instant. This generates a computed measured torque value that includes an uncancellable error. Pulsating torque measurements using only the motor terminal data without the requirement of additional search coils or Hall-effect sensors are a convenient approach to obtain the air gap torque value. This method is further studied for the purpose of understanding the source of its possible errors