Can a VFD be used on any motor?

Time:2022-11-8 Category:Technical Knowledge

1. VFD application

1.1 Petroleum:

oil transfer pump, electric submersible pump, injection pump, oil pumping unit, etc.

1.2 Chemical industry:

extruders, film conveyors, mixers, compressors, blowers, sprayers, pumps, etc.

1.3 Steel:

rolling mill, roller table, fan, pump, crane, ladle car, converter tilting, etc.

1.4 Metallurgical industry:

rolling mill, roller table, blast furnace fan, pump, hoisting machinery, blast furnace feeding, steel mill polishing, etc.

1.5 Electricity:

Blowers for boiler drums, feed pumps, centrifugal mixers, conveyor belts, pumping power stations, flywheels, etc.

1.6 Mining:

mud pumps, conveyor belts, hoists, cutting machines, excavators, cranes, blowers, pumps, compressors, etc.

1.7 Cement:

rotary kiln, hoisting machinery, blower, pump, main drive motor, conveyor belt, shaft kiln fan, etc.

1.8 Paper industry:

paper machines, pumps, pulverizers, fans, mixers, blowers, etc.

2. Can you use a VFD on a DC motor?

No, the inverter converts alternating current into direct current, and then switches the direct current with electronic components to convert it into alternating current.

The inverter adjusts the voltage and frequency of the output power supply by switching on and off the internal IGBT, and provides the required power supply voltage according to the actual needs of the motor, thereby achieving the purpose of energy saving and speed regulation. In addition, the inverter also has many protection functions. , such as overcurrent, overvoltage, overload protection, etc.

3. Which types of motors that can be used with a VFD?

3.1 AC Asynchronous Wound Rotor Motor

3.2 AC Asynchronous Squirrel Cage Motors

3.3 AC Synchronous Permanent Magnet Motors

3.4 AC Synchronous Brushed or Brushless Motors

4. Can VFD be used on different pole number motors?

Most common motors are 4 pole type. The more poles, the slower the speed, and the larger the volume. Pump or similar working theory motors may require higher speed, while ball mill, or some similar working principle motors might need lower speed. Pole numbers might affect rated current of motor.

VFD can be used on different pole number motors. One notice: when we choose a VFD for motor, rated current shall be considered.

5. How to choose a suitable VFD for a motor?

5.1 Voltage

First, select the appropriate voltage, there are single-phase 220V, three-phase 220V, three-phase 380V (to 480V).

5.2 Current

Choose according to the rated current of the motor. The rated output current of the inverter cannot be lower than the rated current of the motor. Select the same for light load, and increase one power for heavy load.

5.3 Working Conditions

If the inverter needs to run with a long cable, we should suppress the influence of the long cable on the coupling capacitance to avoid insufficient output of the inverter. Therefore, in this case, the capacity of the inverter should be increased by one power or put an output reactor at the output end of the inverter.

If interference exists in the working environment, filters will be considered.

6. VFD effect on motor

6.1 Advantage

6.1.1 Control the starting current of the motor to achieve soft start.

6.1.2 The running speed is adjustable to improve product quality.

6.1.3 Adjustable torque limit for equipment protection.

6.1.4 Reduce energy consumption and achieve energy saving operation.

6.1.5 The running direction of the equipment is reversible, and it is easy to realize forward and reverse operation.

6.2 Disadvantage

6.2.1 When the output frequency of the inverter is very low, the ordinary asynchronous motor will heat up seriously. Therefore, ordinary motors cannot run for a long time when the frequency is relatively low.

6.2.2 The magnetic circuit of the motor is easy to saturate in the mode of inverter voltage frequency (U/F) control. This result is also manifested in the fact that the operating temperature of the motor rises too high, which will cause the motor to heat up rapidly in the voltage-frequency control mode, which will reduce the service life of the motor windings over time.

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