The requirements and influence of the inverter on the motor Applied to standard motors

When the frequency converter drives a standard motor, compared with the industrial frequency power supply, the loss will increase, the low-speed cooling effect will be worse, and the motor temperature rise will increase, so the load of the motor should be reduced at low speed. The allowable load characteristic of ordinary motors is that they can run continuously at 100% load at rated speed. In the case of continuous operation at low speeds with 100% load, consider using variable frequency motors.

Impact of impulse voltage: The impulse voltage caused by the LC resonance of the wiring will be added to the stator winding of the motor. When the impulse voltage is large, the insulation of the motor may be damaged. When the single-phase inverter is driven, the DC voltage is about 311V, and the high value of the impulse voltage on the motor terminal is twice the DC voltage, and there is no problem in the insulation strength. However, when the three-phase inverter is driven, the DC voltage is about 537V. As the length of the wiring increases, the impulse voltage will increase. It is possible that the insulation may be damaged due to insufficient insulation voltage of the motor. At this time, consider the output of the inverter. An output reactor is installed on the side.

High-speed operation: The electromotive force balance and bearing characteristics of ordinary motors will change during high-dead operation above 50Hz. Please use it with caution. At the same time, if the rated frequency of the motor is exceeded, the torque of the motor will decrease. At this time, the motor is in the state of constant power regulation. If in doubt, please consult the technical department.

Torque characteristics: When the inverter is driven, the torque characteristics are different from those of the industrial frequency power supply. The torque characteristics of the mechanical load must be confirmed.

Mechanical vibration: The whole series adopts high carrier wave PWM control, the motor vibration is small, basically the same as the industrial frequency power supply. But there will be a certain increase in the following occasions:

A. Resonance with the natural vibration frequency of the machine: Especially when the original constant-speed machine is changed to speed-regulated operation, resonance may occur. The installation of anti-vibration rubber or jump frequency control at the motor end can effectively solve this problem.

B. The residual imbalance of the rotating body itself: pay special attention to the high speed above 50.00Hz.

Noise: It is basically the same as when driven by a power frequency power supply. Electromagnetic noise can be heard during low carrier operation, which is a normal phenomenon; but when the speed is higher than the rated speed of the motor, the mechanical noise and the noise of the motor fan are more obvious.

Applied to special motors

Underwater motor: Generally, the rated current of the underwater motor is larger than that of the standard motor. Pay attention to the rated current of the motor when selecting the inverter capacity. In addition, when the wiring distance between the motor and the inverter is long, the inverter may cause a fault alarm due to excessive leakage current. At this time, consider installing an inverter output reactor; when the wiring distance is long, it will also cause motor torque. For descending, a thick enough cable must be equipped.

Explosion-proof motor: When driving an explosion-proof motor, the explosion-proof inspection after the motor and the inverter are matched is necessary. The general-purpose inverter itself is a non-explosion-proof structure. If the same general-purpose inverter is used, the inverter needs to be placed in a non-explosion-proof place. Motor with reducer: Due to different lubrication methods and manufacturers, the continuous use speed range is also different. Especially in the case of oil lubrication, there is a risk of burnout due to insufficient oil lubrication during continuous operation in the low speed range. In addition, when the high speed exceeds 50Hz, please consult the motor and reducer manufacturers.

Synchronous motor: The starting current and rated current are larger than standard motors. Please pay attention to the selection of the inverter capacity when using the inverter. It is recommended to enlarge the first-level selection. When multiple units are controlled, asynchronous phenomenon occurs when several synchronous motors are gradually put into use. It is not recommended to carry multiple units with one unit.

Single-phase motors: Single-phase motors are generally not suitable for inverter speed control. In the capacitor starting mode, the capacitor is impacted by high-frequency current, which may be damaged, and the starting capacitor is likely to cause over-current faults when the inverter starts; in the split-phase start mode and reverse connection start mode, the internal centrifugal switch will not operate, If the starting coil is burnt, please try to use a three-phase motor. If in doubt, please consult the technical department.

Vibrating machine: The vibrating machine is a motor with an unbalanced block installed on the shaft end of a general-purpose motor. The motor current will fluctuate during operation. When selecting the capacity of the inverter, the current must be within the rated current of the inverter.