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Under normal circumstances, the cage rotor motor will be designed according to the frequency conversion design, and driven by the frequency converter, and the frequency converter with different performance will be selected for different load characteristics. Now we ask a question: will inverter be used in variable speed motor, wound motor, explosion-proof motor and single-phase motor? What are the requirements for inverters?

Ordinary variable frequency speed regulating motor is based on one pole number, while there are two or more basic speeds of variable pole multi speed motor, such as 2 / 4, 4 / 6, 4 / 6 / 12 and so on. If the inverter is used to supply the pole changing motor, there are some key control contents in both the control point of view and the pole changing process.

When the number of poles of the motor is switched, it should be carried out in the stop state of the motor, otherwise the protection action of excessive current will occur due to the change of current.

The power of variable pole multi speed motor varies greatly under different number of poles, so the selection of frequency converter should follow the principle of high power, and the capacity of frequency converter should be able to meet the operation requirements under the condition of high power.

For the motor body, the speed of the motor will change greatly due to the change of the power frequency when it is driven by the frequency converter. From the perspective of ventilation and heat dissipation of the motor body, the compliance of the temperature rise of the winding in the low-frequency state and the compliance of the mechanical strength of the rotating parts in the high-speed state should be considered.

For the frequency converter used in explosion-proof occasions, the frequency converter should be integrated with the motor body for explosion-proof combination, and can only be used after necessary verification.

If the winding motor is driven by the frequency converter, the rotor part can be short circuited, that is, the rotor series resistance mode is not used, but the current increase brought by the frequency conversion driving process must be balanced by reducing the capacity. At the same time, compared with the cage motor, the winding motor has smaller impedance, which is prone to trip due to harmonic current; The setting of acceleration time is longer than that of cage motor, so it is not recommended to drive winding motor with frequency converter.

For the common single-phase motor, the starting winding must be coordinated, so it is not suitable to use frequency conversion starting, and the operation control can be completed by a special frequency converter.