Energy saving device supplier reminds you: how to choose different frequency converter for load? If there is special frequency converter for load, select special frequency converter; if not, you can only choose general frequency converter.
So what are the three different load modes of frequency converter? People often divide the load in practice into constant torque load, constant power load and fan and pump load.
Constant torque load:
The torque TL is not related to the speed n, and TL remains basically constant at any speed. For example, friction load such as conveyor belt and mixer, potential energy load such as hoist and crane belong to constant torque load.
When the frequency converter drives the constant torque load, it needs to run at low speed and steady speed, so that the torque can be large enough and the overload capacity can be sufficient. Finally, the heat dissipation of standard asynchronous motor should be considered to prevent the motor from heating too high.
Constant power load:
The torque of paper machine, uncoiler and other specifications is inversely proportional to the speed n, which is the constant power load.
The constant power property of the load varies within a certain speed. When flux weakening speed regulation, 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 minimum capacity of motor and frequency converter is when the range of constant power and constant torque of motor is the same as that of load.
Fan and pump load:
With the decrease of rotating speed, the torque of fan and water pump decreases according to the square of rotational speed, and the power is proportional to the third power of speed. When saving electricity, we need to use frequency converter to adjust air volume and flow. Because the power required at high speed increases rapidly with the speed, the fan and pump load should not be allowed to operate beyond the power frequency.
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