The Requirements And Influence Of The Inverter On The Motor

When the inverter drives a standard motor, compared with the power frequency power supply, the loss will increase, the low-speed cooling effect will become 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 with 100% load at rated speed, and the use of variable frequency motors should be considered in the case of 100% load continuous operation at low speed.

Impact of surge voltage

The impulse voltage caused by the LC resonance of the wiring will be applied to the stator winding of the motor, and the insulation of the motor may be damaged when the impulse voltage is large. If the insulation withstand voltage of the motor is insufficient and the insulation is damaged, it should be considered to install an output reactor on the output side of the inverter.

high speed operation

The electromotive force balance and bearing characteristics of ordinary motors will change when running at high speeds above 50Hz. At the same time, the motor torque will drop when the motor's rated frequency is exceeded, and the motor is in a constant power regulation state at this time.

moment characteristics

When driven by an inverter, the torque characteristics are different from those when driven by a commercial power supply, and the torque characteristics of the mechanical load must be confirmed.

mechanical vibration

Motor vibration will increase to a certain extent in the following situations:

A. Resonance of the natural vibration frequency of the machine: When the constant speed operation is changed to the speed regulation operation, resonance may occur, and the vibration-proof rubber or jump frequency control at the motor end can effectively solve this problem.

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

noise

Basically the same as when the power frequency power supply is driven, electromagnetic sound can be heard during low carrier operation, which is a normal phenomenon. However, 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.

Pole-changing motor:

Because the rated current of the motor is different from that of the standard motor, the inverter should be selected after confirming the maximum current of the motor. The number of poles must be switched after the inverter stops outputting. Switching the number of poles during operation will cause protection actions such as overvoltage and overcurrent, and the inverter will stop due to failure.

Underwater motor:

Generally, the rated current of the underwater motor is larger than that of the standard motor. When the wiring distance between the motor and the inverter is long, it may cause the inverter fault alarm due to leakage. At this time, it is necessary to consider installing the inverter output reactor; If it is longer, it will also cause the motor torque to drop, so a thick enough cable should be used.

Explosion-proof motors:

When driving an explosion-proof motor, the explosion-proof inspection after the motor and the inverter are matched is necessary. Xilin general-purpose inverter itself is of 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 the different lubrication methods and manufacturers, the speed range for continuous use 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.

Synchronous motor:

The starting current and rated current are larger than those of standard motors. Please pay attention to the selection of the inverter capacity when using the inverter. It is recommended to enlarge one-level selection. When several synchronous motors are controlled, asynchronous phenomenon occurs when several synchronous motors are gradually put into operation.

Single-phase motors:

Single-phase motors are generally not suitable for frequency converter speed regulation. In the capacitor startup mode, the capacitor is impacted by high-frequency current and may be damaged, and the startup capacitor is likely to cause an overcurrent fault when the inverter starts. In the split-phase start mode and the reverse connection start mode, the internal centrifugal switch will not operate, and the start coil will be burned. Please try to use a three-phase motor instead.

Vibrator:

The vibrating machine is a motor with an unbalanced weight added to the shaft end of the general motor. The motor current will fluctuate during operation. When selecting the inverter capacity, the maximum current should be guaranteed to be within the rated current of the inverter.

Winding motor:

The wound motor is adjusted or started by inserting a resistor in series in the rotor. When using variable frequency speed regulation, short-circuit the rotor winding and use it as a common asynchronous motor.