Energy saving device suppliers remind you: How to choose different frequency converters for loads? If the load has a dedicated frequency converter, choose a dedicated frequency converter. If not, only a universal frequency converter can be selected.
So what are the three different load modes of the frequency converter? People often divide the loads in practice into constant torque loads, constant power loads, and fan and pump loads.
Constant torque load:
The torque TL is not related to the speed n, and TL remains relatively constant at any speed. For example, friction loads such as conveyor belts and mixers, as well as potential loads such as elevators and cranes, all belong to constant torque loads.
When the frequency converter drives a constant torque load, it needs to operate at a low speed and steady speed in order to have sufficient torque and overload capacity. Finally, it is necessary to consider the heat dissipation of standard asynchronous motors to prevent excessive temperature rise.
Constant power load:
The torque of paper machines, uncoiler machines, and other specifications is often inversely proportional to the speed n, which is known as constant power load.
The constant power property of the load varies within a certain speed. When using weak magnetic speed regulation, the maximum allowable output torque is inversely proportional to the speed, which is known as 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 minimum capacity of the electric motor and the frequency converter is when the range of constant power and constant torque of the motor is the same as the range of constant power and constant torque of the load.
Fan and pump loads:
As the speed of equipment such as fans and pumps decreases, the torque decreases by the square of the speed, and the power is proportional to the third power of the speed. When saving electricity, it is necessary to use a frequency converter to adjust the air volume and flow rate through speed regulation. Because the required power increases rapidly with the speed at high speeds, fans and pumps should not be allowed to operate beyond the power frequency.