Characteristics of three different loads of frequency converter

How to choose different frequency converters for loads? If there is a dedicated frequency converter for the load, you can give priority to the dedicated frequency converter. If not, choose a general frequency converter.

Three different load characteristics of frequency converters: constant torque load, constant power load, fan and water pump load.

Constant torque load:

Torque TL has no connection with speed n, and TL remains basically constant at any speed. For example, friction loads such as conveyor belts and mixers, and potential loads such as hoists and cranes are all constant torque loads.

When the frequency converter drives a constant torque load, it needs to run at a low and steady speed so that the torque can be large enough to have sufficient overload capacity. In addition, the heat dissipation of the standard asynchronous motor must be considered to prevent the motor from overheating.

Constant power load:

The load whose torque TL is inversely proportional to the speed n is a constant power load. Such as papermaking machines, unwinding machines and other loads.

The constant power nature of the load changes within a certain speed. When weak magnetic speed regulation is used, the maximum allowable output torque is inversely proportional to the speed, which is constant power speed regulation.

When the speed is very low, due to the limitation of mechanical strength, the load torque TL has a maximum value, so it will become a constant torque property.

The capacity of the motor and the capacity of the inverter are the smallest when the range of the motor's constant power and constant torque is the same as the range of the load's constant power and constant torque.

Fan and pump loads:

For equipment such as fans and water pumps, as the speed decreases, the torque decreases according to the square of the speed, and the power is proportional to the cube of the speed. When saving electricity, it is necessary to use the inverter to adjust the air volume and flow rate by speed regulation. Because the power required at high speed increases rapidly with the speed, fans and pumps should not be allowed to operate at over-powered frequency.