In the practical application of frequency converter, some unexpected problems will appear from time to time, mostly because motor users don’t know much about the matching relationship between frequency converter and motor, especially in some relatively special motor applications, similar problems are more concentrated.
(1) When the inverter is used to control the pole-changing motor, special attention must be paid to the capacity compliance of the inverter, so as to ensure that the rated current of the motor under different pole numbers is not higher than the rated output current allowed by the inverter, that is, the rated current of the inverter cannot be lower than the rated motor of the maximum gear of the motor; In addition, the pole number conversion of the motor should be carried out when the motor stops working, so as to prevent the misoperation of overvoltage or overcurrent protection.
(2) The frequency converter used to control high-speed motors, because the torque of high-speed motors is relatively small, and the higher harmonics will increase the current value. Therefore, when selecting a frequency converter, the capacity of the frequency converter should be larger than that of a common motor.
(3) When the explosion-proof motor matches the frequency converter, it should match the explosion-proof frequency converter according to the actual demand, otherwise it should be placed in a non-dangerous place.
(4) When the frequency converter is used for the control of wound rotor motor, it is similar to the control of high-speed motor. Because the winding impedance of this kind of motor is relatively small, it should also match the frequency converter with relatively large capacity; Moreover, due to the particularity of the wound rotor, the speed after frequency conversion must match the mechanical tolerance of the motor rotor.
(5) When the inverter is used to control the submersible pump motor, the rated current of this kind of motor is larger than that of the ordinary motor. Therefore, when selecting the inverter, it is necessary to ensure that the rated current allowed by the inverter is larger than that of the motor, and it is impossible to simply select the type according to the ordinary motor.
(6) For motor operating conditions with variable loads, such as compressors and vibrators, such motors generally have service factor requirements, that is, the load and motor current are greater than the peak value of standard power. When selecting a frequency converter, the matching relationship between its rated output current and peak current should be fully considered to prevent the misoperation of protection actions during operation.
(7) When the inverter controls the synchronous motor, because the power of the synchronous motor is adjustable, the capacity of the synchronous motor can be smaller than that of the control power frequency motor, which is generally reduced by 10% to 20%.
In addition to the above contents, there may be motors with other uses and characteristics. When selecting a frequency converter, we must fully consider the motor characteristics and operating conditions, and determine the frequency conversion parameters and applicability after comprehensive evaluation.
Post time: Dec-22-2022