The supplier of frequency converter supporting equipment reminds you that when driving a standard motor with a frequency converter, compared with the power supply, the loss will increase, the low-speed cooling effect will deteriorate, and the motor temperature rise will increase. Therefore, the load on the motor should be reduced at low speeds. The allowable load characteristic of a regular motor is that it can operate continuously at 100% load at rated speed, and variable frequency motors should be considered for low-speed 100% load continuous operation.
The impact of impulse voltage:
The surge voltage caused by LC resonance in the wiring will be applied to the stator winding of the motor, and when the surge voltage is high, it may damage the motor insulation. When driven by a single-phase frequency converter, the DC voltage is about 311V, and the highest value of the impulse voltage at the motor terminals is twice the DC voltage. There is no problem with the insulation strength. However, in the case of three-phase frequency converter drive, the DC voltage is about 537V. As the wiring length increases, the impulse voltage will increase, which may cause insulation damage due to insufficient motor insulation withstand voltage. At this time, it should be considered to install an output reactor on the output side of the frequency converter.
High speed operation:
The balance of electromotive force and bearing characteristics may change during high dead running of ordinary motors above 50Hz. Please use with caution. At the same time, if the motor operates beyond its rated frequency, the motor torque will decrease, and the motor will be in a constant power regulation state.
Torque characteristics:
When driven by a frequency converter, the torque characteristics are different from those driven by a power frequency source, and the torque characteristics of mechanical loads must be confirmed.
Mechanical vibration:
A、 Resonance with the natural vibration frequency of machinery: Especially when machinery that originally operated at constant speed is changed to speed regulation, resonance may occur. Installing shock-absorbing 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 when operating at high speeds above 50.00Hz.
Noise:
Basically the same as when driven by a power supply at the same frequency, electromagnetic sound 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, mechanical noise and motor fan noise are more obvious.
Applied to special motors
Variable pole motor:
Due to the difference between the rated current of the motor and the standard motor, it is necessary to confirm the maximum current of the motor before selecting a frequency converter. The switching of the number of poles must be carried out after the frequency converter stops outputting. Switching the number of poles during operation may result in protective actions such as overvoltage and overcurrent, causing the frequency converter to malfunction and shut down.
Underwater motor:
Generally, the rated current of underwater motors is higher than that of standard motors. When selecting the capacity of the frequency converter, attention should be paid to the rated current of the motor. In addition, when the wiring distance between the motor and the frequency converter is long, it may cause a frequency converter fault alarm due to excessive leakage current. At this time, it should be considered to install a frequency converter output reactor; When the wiring distance is long, it can also cause a decrease in motor torque, and a sufficiently thick cable should be used.
Explosion proof motor:
When driving explosion-proof motors, it is necessary to conduct explosion-proof inspections after the motor and frequency converter are matched. If using the same universal frequency converter, it is necessary to place the frequency converter in a non explosion proof location.
Motor with reducer:
Due to differences in lubrication methods and manufacturers, the speed range for continuous use also varies. Especially during oil lubrication, there is a risk of burning out due to insufficient oil lubrication during continuous operation in the low-speed range. When the speed exceeds 50Hz, please consult the motor and gearbox manufacturers.
Synchronous motor:
The starting current and rated current are higher than standard motors. When using a frequency converter, please pay attention to the selection of the frequency converter capacity. Suggest enlarging the first level selection. When multiple synchronous motors are gradually put into operation, asynchronous phenomena may occur. It is not recommended to have one motor with multiple motors.
Single phase motor:
Single phase motors are generally not suitable for frequency converter speed regulation. When using the capacitor starting method, the capacitor may be damaged due to high-frequency current impact, and the starting capacitor can easily cause overcurrent faults during the start-up of the frequency converter; When starting in phase separation and reverse connection, the internal centrifugal switch will not operate and may burn the starting coil. Please try to use a three-phase motor instead.
Vibration machine:
Vibration machine is a motor that is equipped with an unbalanced block at the shaft end of a universal motor. During operation, the motor current will fluctuate and change. When selecting the capacity of the frequency converter, the maximum current should be ensured to be within the rated current of the frequency converter.
Winding motor:
A wound motor is controlled or started by inserting a resistor in series into the rotor. When using variable frequency speed regulation, short-circuit the rotor winding and use it as a regular asynchronous motor.