Measurement Technique for Magnetic Flux in a Motor Core Under Operating Conditions

Accurate evaluation of magnetic properties of a motor core under actual operating conditions is necessary for the design of efficient motors. To elucidate phenomena that occur in a motor core with high accuracy, we specifically examined visualization of the magnetic flux flow in the laminated core. Evaluations are usually conducted with a specimen of the electrical steel sheet, which is used for the motor core under a flux flow condition similar to that in an actual motor core. However, such simplistic methods cannot predict the actual magnetic phenomena occurring in the motor core under operating conditions. Therefore, we developed a measurement method using a magnetic flux sensor that is thinner than an electrical steel sheet. It can measure the 3-D magnetic flux flow in the motor core under operating conditions. This sensor can be placed in the narrow space of laminated electrical steel sheets and can be designed so that it does not disturb the magnetic flux flow in the motor core. Furthermore, the sensor has high electric noise tolerance in an operating motor. As described herein, we explain the development of an evaluation method for measuring the magnetic flux density inside the motor core in a rotation condition. Moreover, we compared results obtained from measurements and simulation. Results show that the proposed measurement method is useful for magnetic flux density measurements in a motor core under operating conditions.