Inverter brand manufacturers say there are two main aspects of the use of inverters.

1. Use the frequency converter as a speed adjustment function to meet the control requirements. It is mainly used for speed control under constant torque and constant power load conditions. In this case, the choice of frequency converter first considers the design selection of the equipment, because this is to achieve the control strategy. Therefore, the frequency converter brand manufacturer believes that the selection type and the motor have a higher degree of coordination, and there are feasible examples and previous experience as a reference.

2. The use of frequency converters for energy saving has become increasingly popular in recent years, and its application in industries such as liquid chemical industry has become more and more extensive. In addition to the motor control of newly built equipment, old production equipment in use is also being transformed one after another. The purpose is to save energy consumption by reusing motors. China's liquid chemical industry has a large base, and most of the equipment used is general control of low-voltage motors with low efficiency.

The purpose of using frequency converters for low-voltage motors in liquid chemical industry is not to control speed, but to save energy. Liquid chemical motors are mainly used to control booster pumps and blowers. Frequency converter brand manufacturers believe that the use of booster pumps in liquid chemical industry accounts for more than 90% of low-voltage motors, which is a large part of the electricity used in liquid chemical industry.

The pumps used in liquid chemistry have no special requirements for speed control. In terms of industrial production, the running speed of the on-site water pump has nothing to do with production control. The frequency converter is used to adjust the speed of the motor. So what is the relationship between speed and energy saving? This is a control method applied to the frequency converter, that is, the proportional control of U/F=constant. From the perspective of energy, the voltage of the motor decreases as the frequency decreases, so that the power of the motor becomes smaller and energy saving is achieved.

The classic mode of liquid chemical production control is that the motor guides the pressure pump to control the fluid, and the liquid passes through the regulating valve of the pipeline to achieve flow and pressure control, reaching the next production equipment, and realizing safe and stable automatic production.

From the perspective of fluid mechanics, the liquid flows through the pipeline, and the valve overcomes the resistance to consume the mechanical energy of the fluid, especially the mechanical energy consumed by the regulating valve accounts for a large proportion. The energy consumed by the motor is wasted in the process of liquid transportation. From the perspective of energy saving, there is room for transformation in this regard.

The function of the frequency converter U/F=constant just meets this condition, so the frequency converter is suitable for saving liquid chemical energy consumption, so the frequency converter is widely used in the energy-saving transformation of old equipment.

However, in actual use, the frequency converter brand manufacturers have found a big problem.

According to the speed regulation principle of the motor, the frequency is proportional to the speed, and the axial power is proportional to the cube of the speed. According to the principle of fluid mechanics: the liquid flow is proportional to the speed, and the pressure is proportional to the square of the speed.

The inverter brand manufacturer summarizes: After using the inverter motor to replace the regulating valve, the signal returned by the liquid flow in the pipeline is linearly consistent with the frequency output by the inverter, but the pressure of the liquid corresponds to the square of the frequency output by the inverter. In other words, if the inverter output frequency becomes smaller, it is just suitable for liquid flow control, but the width of the liquid pressure reduction is much larger than the flow.