It is wrong to use the inverter to save power.
The inverter gives the impression that power can be saved by using the inverter.
In fact, the reason why the inverter can save electricity is because it can regulate the motor. If the inverter is a power-saving control product, then all the speed control equipment can also be said to be a power-saving control product. The inverter is only slightly higher in efficiency and power factor than other speed control devices.
Whether the inverter can achieve power saving is determined by the speed regulation characteristics of its load. For loads such as centrifugal fans and centrifugal pumps, the torque is proportional to the square of the speed, and the power is proportional to the cube of the speed. As long as the valve is used to control the flow, and it is not working at full load, it can be saved to speed control. When the speed drops to 80% of the original, the power is only 51.2% of the original. It can be seen that the application of the frequency converter in such loads has the most obvious power saving effect. For loads such as Roots blowers, the torque is independent of the magnitude of the speed, ie the constant torque load. If the air volume is adjusted by using the venting valve to remove the excess air volume, and the speed control operation is changed, the power saving can also be realized. When the speed drops to 80% of the original, the power is 80% of the original. It is much less efficient than the application in centrifugal fans and centrifugal pumps. For constant power loads, the power is independent of the magnitude of the speed. Constant power load of cement plant, such as batching belt scale, under the condition of set flow rate, when the material layer is thick, the belt speed is slowed down; when the material layer is thin, the belt speed is accelerated. The application of the inverter in this type of load cannot save electricity.
Compared with the DC speed control system, the DC motor is more efficient than the AC motor and has a high power factor. The digital DC governor is as efficient as the inverter. Even the digital DC governor is slightly more efficient than the inverter. Therefore, it is claimed that the use of AC asynchronous motors and frequency converters is more energy efficient than the use of DC motors and DC converters. Theory and practice have proved that this is not true.
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