Suppliers of frequency converter supporting equipment remind you that selecting the correct frequency converter supporting equipment can ensure the normal operation of the frequency converter drive system, provide protection for the frequency converter and motor, and reduce the impact on other equipment.
Peripheral devices usually refer to accessories, which are divided into conventional accessories and specialized accessories, such as circuit breakers and contactors, which are conventional accessories; AC reactors, filters, braking resistors, braking units, energy feedback devices, DC reactors, and output AC reactors are specialized accessories.
(1) Selection of standard accessories.
Due to the fact that the starting current of the motor in the frequency converter speed control system can be controlled within a small range, the rated current of the power side circuit breaker can be selected according to the rated current of the frequency converter.
The selection method for contactors is the same as that for circuit breakers. Attention should be paid when using: Do not use AC contactors for frequent starting or stopping (the open/close life of the inverter input circuit is approximately 100000 times): Do not use AC contactors on the power side to stop the inverter.
There is static capacitance to ground inside the frequency converter, motor, and input/output leads, and the carrier frequency used by the frequency converter is relatively high. Therefore, the leakage current to ground of the frequency converter is large, and sometimes it may even cause the protection circuit to malfunction. When using a leakage protector, the following two points should be noted:
One is that the leakage protector should be located on the input side of the frequency converter, behind the circuit breaker;
The second is that the operating current of the leakage protector should be greater than 10 times the leakage current of the line when the frequency converter is not used under the power supply.
(2) Selection of specialized accessories.
The selection of specialized accessories should be based on the requirements in the frequency converter user manual provided by the frequency converter manufacturer, and should not be blindly selected.
The braking unit, also known as the "frequency converter specific energy consumption braking unit" or "frequency converter specific energy feedback unit", is mainly used to control situations with heavy mechanical loads and very fast braking speed requirements. It consumes the regenerated electrical energy generated by the motor through the braking resistor or feeds back the regenerated electrical energy to the power supply.
And energy feedback devices have become a popular choice in frequency converter supporting equipment with the implementation of energy-saving and consumption reducing policies. An energy feedback device is a device that utilizes the mechanical energy (potential energy, kinetic energy) on a moving load to be converted into electrical energy through a motor, and then converted into alternating current by an inverter, rectifier, and filtering circuit. Therefore, energy feedback devices are installed on high-power equipment (cranes, hoists, centrifuges, and pumping units) within the system where potential and kinetic energy often change. It can effectively return the regenerated electric energy of the motor to the AC power grid for use by other surrounding electrical equipment, with a significant energy-saving effect. The general energy-saving rate can reach 20% to 50%.