When the induction motor is in a stopped state for motor maintenance, from an electromagnetic perspective, it is like a transformer. The stator winding connected to the power supply is equivalent to the primary coil of the transformer, and the closed rotor winding is equivalent to the secondary coil of the transformer that has been short circuited; There is no electrical connection between the stator winding and the rotor winding, only a magnetic connection, and the magnetic flux forms a closed circuit through the stator, air gap, and rotor core. At the moment of closing, the rotor has not yet turned due to inertia, and the rotating magnetic field cuts the rotor winding at the maximum cutting speed - synchronous speed, causing the rotor winding to induce the highest possible potential. Therefore, a large current flows through the rotor conductor, generating magnetic energy that counteracts the stator magnetic field, just like the secondary magnetic flux of a transformer needs to counteract the effect of the primary magnetic flux. In order to maintain the original magnetic flux that is suitable for the current supply voltage, the stator automatically increases the current. Because the current of the rotor is high at this time, the stator current also increases significantly, even reaching 4-7 times the rated current, which is the reason for the high starting current. Why is it small after startup: As the speed of the motor increases, the speed of the stator magnetic field cutting the rotor conductor decreases, the induced electromotive force in the rotor conductor decreases, and the current in the rotor conductor also decreases. Therefore, the part of the stator current used to offset the influence of the magnetic flux generated by the rotor current also decreases, so the stator current increases from high to low until normal.

In order to effectively eliminate inefficient motors and accelerate the promotion of high-efficiency motors, the new version of the national standard "Energy Efficiency Limits and Energy Efficiency Grades for Small and Medium sized Three Phase Asynchronous Motors" issued by the National Standardization Administration Committee was implemented in September 2012, which has had a significant impact on the small and medium-sized motor industry. At present, the large-scale production of Y, Y2, and Y3 series three-phase asynchronous motors in China will be prohibited, and the YX3 series high-efficiency three-phase asynchronous motors that enjoy the national benefit project may no longer receive policy subsidies. The research and development and promotion of high-efficiency motors are like arrows in a string, with unprecedented attention in the industry.

In the electrical equipment of electric motors, insulation materials are the weakest link. Insulating materials are particularly susceptible to the influence of high temperatures, which can accelerate aging and damage them. Different insulation materials have different heat resistance properties, and electrical equipment using different insulation materials have different abilities to withstand high temperatures. Therefore, general electrical equipment specifies the maximum temperature at which it operates.