Constant power load
The torque requested by machine tool spindles and winding machines, uncoilers, etc. in rolling mills, paper mills, plastic film consumption lines, etc., is roughly inversely proportional to the speed and belongs to constant power loads. The constant power nature of the load should be in terms of a certain range of speed changes. When the speed is very low, it will change to a constant torque load at low speed due to the limitation of mechanical strength. When the motor adjusts the speed in constant magnetic flux, it is a constant torque speed regulation; In the case of weak magnetic speed regulation, it is a constant power speed regulation.
Fan and pump loads
Fans, water pumps, oil pumps and other equipment rotate with the impeller. As the speed decreases, the torque decreases by the square of the speed, and the power required by the load is proportional to the third square of the speed. When the required air volume and flow rate are reduced, VFD can adjust the air volume and flow rate by adjusting the speed, which can greatly save electricity. Since the power required for high speed increases too quickly with speed, fan and pump loads should not be operated at an overrun frequency.
Constant torque load
Always constant or fundamentally constant at any speed. When the VFD drags the load of constant torque performance, the torque at low speeds should be large enough and have sufficient overload capacity. If stable operation at low speed is required, the heat dissipation performance of the motor should be considered to prevent the motor from burning due to excessive temperature rise.