The energy-saving of low voltage inverter is mainly reflected in the application of fans and pumps. In order to ensure the reliability of production, various production machinery leave a certain amount of margin when designing power drives. When the motor cannot run at full load, in addition to meeting the power drive requirements, the surplus torque increases the consumption of active power, causing waste of electrical energy. The traditional speed regulation methods for equipment such as fans and pumps are to adjust the inlet or outlet damper, valve opening to adjust the air volume and water supply. Their input power is large, and a large amount of energy is consumed in the flow-cutting process of the damper and valve. When using frequency conversion speed regulation, if the flow rate requirement decreases, it can be satisfied by reducing the speed of the pump or fan.
It is known from fluid mechanics that P (power) = Q (flow rate) × H (pressure), the flow rate Q is proportional to the first power of the speed N, the pressure H is proportional to the square of the speed N, and the power P is proportional to the cube of the speed N. If the efficiency of the water pump is constant, when the flow rate requirement is reduced, the speed N can decrease in proportion, and at this time, the shaft output power P decreases in proportion to the cube of the speed. That is, the power consumption of the water pump motor is approximately proportional to the cube of the speed. Therefore, when the required flow rate Q decreases, the output frequency of the low voltage inverter can be adjusted to make the motor speed n decrease in proportion. At this time, the power P of the motor will decrease significantly in cubic relationship, which is 40% to 50% more energy-saving than adjusting the damper and valve, thus achieving the purpose of energy-saving.
For example: The power of a centrifugal pump motor is 55 kW. When the speed decreases to 4/5 of the original speed, its power consumption is 28.16 kW, saving 48.8% of electricity. When the speed decreases to 1/2 of the original speed, its power consumption is 6.875 kW, saving 87.5% of electricity.
Reactive power not only increases line loss and equipment heating, but more importantly, the reduction of power factor leads to the reduction of active power in the grid. A large amount of reactive power consumption is in the line, which makes the utilization efficiency of the equipment low and waste serious. After using the low-voltage inverter frequency conversion speed regulation device, due to the role of the internal filtering capacitor of the converter, the reactive power loss is reduced, and the active power of the grid is increased.
Hard starting of motors causes serious impact on the power grid, and also requires excessive capacity of the power grid. The large current and vibration generated during starting cause serious damage to dampers and valves, which is extremely unfavorable for the service life of equipment and pipelines. After using the energy-saving device of frequency conversion, the soft start function of the low voltage soft starter is used to make the starting current start from zero, and the maximum value does not exceed the rated current. This reduces the impact on the power grid and the demand for power supply capacity, prolongs the service life of equipment and valves, and saves equipment maintenance costs.