The nameplate of the motor product specifies several important parameters such as the rated power, rated voltage, rated current and rated frequency of the motor. Among the several rated parameters, the rated power is the basic parameter with the rated power as the basic framework. For industrial frequency motors, when the rated voltage, rated current and rated frequency of the motor meet the requirements, the motor can operate normally. Under the corresponding rated state, the motor can output the rated torque, which is specifically reflected in the motor's ability to drag the load size. For variable frequency motors, due to the changing characteristics of the input power frequency, the overall operation mode of the motor is controlled for the operating conditions of constant torque and constant frequency to ensure the safety of the motor operation.

Simply summarizing these rated parameters of the motor, they can basically be classified into two parts: mechanical safety and electrical safety.

The mechanical safety of the motor is characterized by the rated torque. The size of the motor torque directly affects the state of the bearing system and the shaft. For example, a heavy-loaded motor must be matched with a bearing that can carry a larger load. When the motor torque is large, it will have an adverse effect on the operating quality of the bearing. At the same time, in addition to the operating quality of the bearing system, a larger torque may cause the shaft to bend or even break, especially for welded shafts, the degree of adverse effects will be greater.

The electrical safety of the motor is characterized by the rated voltage and rated current. When the rated voltage is high, the inter-turn voltage of the winding increases, which directly leads to the unreliability of the inter-turn insulation; when the motor current is too high, the winding will directly affect the current density due to the large current factor. The large current density will cause the conductor to heat up seriously, and the final consequence is the temperature rise, which further threatens the electrical reliability of the motor.

Therefore, whether it is an industrial frequency motor or a variable frequency motor, the safety of its operation revolves around mechanical safety and electrical safety. Any deviation from the rated conditions will have an adverse effect on the motor.