In the application process of inverter power supply to motor, what problems often encounter?
Frequency converter is a device that converts the power frequency power supply into other frequency power supply. Our country's power frequency is 50 Hz, in the field of motor, in order to change the motor speed, or other performance changes, many motors use inverter power supply.
The frequency converter is a kind of conversion device used with the frequency conversion motor. From the configuration of the circuit, the frequency converter is between the motor and the power supply. The motor with different load characteristics should match the frequency converter with different performance.
Relationship between voltage and frequency of frequency converter
Taking the asynchronous motor as an example, the torque of the motor is the result of the joint action of the motor flux and the rotor current. Taking the rated frequency as the boundary, when the frequency of the power supply is reduced, if the input voltage of the motor is kept unchanged, the magnetic flux of the motor will be saturated, and in serious cases, the motor winding will be burned. Therefore, when the power frequency is reduced, the input voltage of the motor should be reduced at the same time. The principle is to control the magnetic flux of the motor unchanged. This control method is generally used in the loads of fans and pumps.
For the power frequency motor, if the voltage is lower than the rated voltage, if the same power is to be output, the current of the motor will increase a lot, especially for the motor running on the temporary line, which leads to many winding burning problems. Then, for the motor powered by frequency converter, when it is running at low speed, if it is required to output the same power, that is, the constant power running state, there is also the problem of current increase. However, if it is running at constant torque, the current of the motor will not change much.
The control key of 60 Hz motor using 50 Hz power supply test
For the newly built test institutions, most of them are equipped with variable frequency power supply, which can be tested according to the actual frequency of the motor. However, for some old test equipment or some repair units, they do not necessarily have the conditions for variable frequency test. How to test a 60Hz motor?
According to the theoretical inference in this paper, when the power frequency 50 Hz power supply test is adopted, the voltage should be reduced, and the voltage test should be applied according to the calculated value of motor rated voltage divided by 1.2.