Research On Measurement Of Stator Core Magnetic Characteristics And Iron Loss Of An Induction Motor At Each Manufacturing Process

Electrical steel sheets that are widely used in the manufacture of electrical equipment, such as motor, transformer and so on. The magnetic properties of electrical steel sheets are usually measured by such as the Epstein frame tester or the single sheet tester based on the IEC standard or the National standard. These methods can only measure the magnetic properties of electrical steel sheet under uniform distribution of magnetic flux density.However, during the manufacturing process of the actual electrical machine, mechanical stress and the thermal stress caused by cutting process and the welding process can degrade or even ruin the magnetic performance of the sheet then increase iron loss. Therefore, the magnetic properties of electrical steel sheet under this condition and the pure sheet are quite different, thus it cannot be replaced by the pure sheet during the analysis. In order to study the effect of the magnetic characteristics of the electrical machine during the different manufacturing process, the B-H characteristics and iron loss of the actual electrical machine should be measured.Actually, due to the complex shape of the actual stator core, the conventional magnetic properties measurement method cannot be applied directly. Based on this reason, this paper proposed a new iron loss measurement system which based on the auxiliary core. Through the optimal design of the auxiliary core, the distribution of magnetic flux density become uniform along the magnetic flux path, thus meet the requirements of the measurement.In the system, the magnetic flux density B is calculated based on the induced voltage of the B coil which wound on the auxiliary core and the magnetic field strength H is calculated by exciting current. The iron loss obtained by the Poynting theorem formula. The configuration of the stator core loss measurement system includes PC, DAQ board, Low-pass Filter, Power Amplifier, Isolation Amplifier, stator core, B-coil and shunt resistor. Based on the hardware platform, the measurement interface used NI company’s Labview software for completing the following functions: applying exciting voltage signal for the stator, waveform control of exciting voltage, signal picking-up of the B coil and shunt resistor, calculating the loss of stator and data storage.The magnetic characteristic and the iron loss of the actual stator core can be measured by the measurement system at each manufacturing process including original electrical steel sheet,laminated core, unwound core wound core and housing-inserted core. Finally, the iron loss and the B-H characteristics are compared by each manufacturing stage. And the influence of different stages on the motor are discussed.