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First, the pump usage overview

    The load of production equipment of industrial enterprises is mostly AC asynchronous motor, and the power consumption accounts for about 65% of the total power consumption of the enterprise. In particular, the efficiency of the pump load is relatively low. After China joined the WTO in 2002, enterprises must reduce costs. To improve economic efficiency. In order to enhance competitiveness, in reducing production costs, saving electricity is an important economic link. For example, for a water supply station, the water supply system is adjusted according to the demand of water consumption. The pump is used to adjust the flow rate of the valve, which requires special personnel to be on duty. In different situations, the valve is opened and closed. The labor intensity is large. At the same time, due to the forced throttling of the valve, the pump forms a vortex impact, which generates strong vibration and noise, which increases the unfavorable loss of the service life and maintenance of the pump. Then, because the torque of the motor is basically constant, the water supply pressure formed by this adjustment mode is high, causing serious throttling power loss, and the efficiency of the pump is lowered, resulting in waste of power.

Second, the water pump frequency conversion energy-saving transformation of the speed regulation performance

    According to the similar principle of the water pump, when the speed changes, the flow rate is proportional to the speed. The head is proportional to the square of the speed. The shaft power is proportional to the cube of the speed. It is concluded that the main performance of the pump when the speed of the same pump changes. The parameters will change according to the above proportional law, and the efficiency can be kept basically unchanged during the change process. If the pump unit speed is adjustable, we can change the speed of a certain pump to adapt to the change of water demand at that time, so as to avoid The motor unit is overloaded by the pump unit in the low-efficiency area, and on the other hand, the waste caused by the high water supply pressure can be avoided. At the same time, as the speed of the water pump slows down, the shaft power is greatly reduced, and the input power of the motor is also reduced. This is the energy-saving effect of the speed-regulating water pump in the water supply system.

Third, the pump frequency conversion energy-saving transformation deceleration of the pump principle

    According to the speed relationship in the working principle of the AC motor, n=60f(1-s)/p, it is concluded from the formula that the synchronous frequency of the motor can be smoothly changed by uniformly changing the power frequency of the stator winding of the motor. As the motor speed becomes slower, the shaft power is reduced accordingly, and the motor input power is also reduced. This is the energy-saving effect of the pump speed regulation.

    The AC motor speed property is a slightly downward curve. As shown in Figure A, the characteristic of the speed regulation is still a slightly downward curve, which is a set of curves equal to each other at different frequencies, as shown in Figure B:

    It can be seen from Figure A and Figure B that the speed regulation characteristics of the inverter basically maintain the inherent speed characteristics of the motor, which is a characteristic curve parallel to each other at a different frequency.

Frequency control has the following advantages:

1.The slip rate is small, the slip loss is small, and the efficiency can be as high as 90~95%.

2. Smooth and stepless speed regulation, high precision, wide speed range (0~100%), wide frequency range (0~50Hz).

3. The starting torque is large (up to 1.1 times the rated value), and the soft start reduces the impact of the starting current.

4. Improve the grid side power factor.

5. Inverter can use high-speed 16-bit CPU to cooperate with special large-scale integrated circuit, realize V/5 automatic adjustment by software, and have the function of online control with computer programmable controller, which is easy to realize automatic control of production process.

6. easy to install, easy to debug, easy to operate.

7. It is not only suitable for energy-saving speed regulation of pumps and fans, but also suitable for the transformation of old equipment. It has obvious effects on improving process conditions and improving product quality.

Fourth, the pump frequency conversion energy-saving transformation case analysis

In the above case, the motor power is 45KW, one inverter is installed, and the operation is three months, and the power saving effect is obvious.

The life pump water frequency deceleration energy saving test data is shown in Table A and Table B:

  Table A Test data before installing the inverter (f=50Hz)

  Table B Test data before installing the inverter (f=50Hz)

    The peak and