We all know that the principle and type of the vfd,the speed of the three-phase asynchronous motor is N2=N1(1-S)(r/min),
Since N1=60f/Q, there is N2=60f(1-S)Q(r/min),
N1——same frequency speed,
HzQ——motor electrode logarithm,
S - the slip rate.
It can be seen that when the frequency converter is used for speed control, changing the frequency f can change the motor speed N2. The frequency converter used by our company is the more advanced AVF580 series vfd.
The principle is as follows: the three-phase power is converted into a DC voltage by a rectifier, and then the inverter is controlled by the CPU to convert the DC voltage into an AC output whose voltage amplitude and frequency are adjustable, wherein the frequency, voltage, and load current of the output AC are After the detection unit detects and sends it to the CPU, it realizes the automatic control inside the inverter to accurately and reliably adjust the voltage amplitude and frequency of the output power supply. In addition, the signal distribution circuit outputs an alarm signal to achieve high quality and safe operation of the controlled system.
Application of Frequency Control Technology in Circulating Water Pump
There are 3 hot water pumps in the circulating pump house, the actual lifting height is 24m, and it is equipped with 160kW asynchronous motor. In the course of operation, due to the large fluctuation of the water department load, the water supply quantity is large and small, and the change of the water quantity by frequently adjusting the outlet butterfly valve of the pump will inevitably cause a great waste of energy. To this end, we installed the AVF580 vfd(160KW, 380V) on these three pumps. During the production operation, the water pump controlled by the vfd is normally open, and all the outlet butterfly valves of the running pump are kept in the fully open position. The water quantity change is controlled by the frequency conversion speed regulation, and the rotation speed of the water pump changes with the change of the water supply amount. At the same time, the current of the motor also varies with the speed. In order to obtain specific power-saving data, we made a comparison of the power-saving effect. With 10 days as a cycle, the same pump uses the vfd and without the vfd to record the power consumption. Through repeated test comparisons, the power saving data of the pump is measured. In the case of using the vfd, the power consumption of the pump is reduced by 21000 kWh every 10 days. When the vfd is not used, the power consumption of the pump is 33000 kWh every 10 days. In this way, the power saving rate can reach 63.6, and each pump can save 693,000 kWh per year, and the power saving effect is remarkable.