Basic Introduction of inverter

1. frequency converter (Variable-frequency Drive, abbreviation: VFD), also known as Variable frequency Drive or Drive controller, can be translated as Inverter (the same as Inverter in English). Frequency converter is a kind of adjustable speed drive system. It uses frequency conversion drive technology to change the frequency and amplitude of AC motor working voltage to smoothly control AC motor speed and torque, the most common is the AC/AC converter whose input and output are alternating current.

overview: the main circuit is the power conversion part that provides the asynchronous motor with voltage regulating and frequency modulation power supply. The main circuit of the frequency converter can be divided into two categories in general: the voltage type is the frequency converter that converts the DC of the voltage source into AC, the filtering of the DC loop is capacitance. Current type is a frequency converter that converts the DC of current source into AC, and its DC loop filtering is inductance. It consists of three parts, which converts power frequency power into DC power. Rectifier", the" flat wave loop "that absorbs the voltage ripple generated by the converter and inverter, and the" Inverter "that converts DC power into AC power".

Rectifier: recently, converter of diodes are widely used, which converts power frequency power DC power supply. Two groups are also available. Transistor converter constitutes a reversible converter, which can be regenerated due to its reversible power direction.

Inverter:

1. In contrast to the rectifier, the inverter converts the DC power into the AC power of the required frequency, and the 3-phase AC output can be obtained by turning on and off the 6 switching devices at the determined time. The switching time and voltage waveform are illustrated by the voltage-type pwm inverter.

2. The control circuit is a loop that provides control signals to the main circuit of the asynchronous motor (voltage and frequency adjustable). It has a "operation circuit" of frequency and voltage, a "voltage" of the main circuit, the current detection circuit ", the" speed detection circuit "of the motor, the" driving circuit "which magnifies the control signal of the operation circuit, and the" protection circuit "of the inverter and the motor.

(1) operation circuit: compare the external speed, torque and other commands with the current and voltage signals of the detection circuit to determine the output voltage and frequency of the inverter.

(2) voltage and current detection circuit: isolate and detect voltage and current from the main circuit potential.

(3) driving circuit: the circuit that drives the main circuit device. It is isolated from the control circuit to turn on and off the main circuit devices.

(4) speed detection circuit: the signal of the speed detector (tg, plg, etc.) installed on the asynchronous motor reel machine is used as the speed signal and sent to the operation loop, according to the instruction and calculation, the motor can run at instruction speed.

(5) protection circuit: detect the voltage, current and so on of the main circuit. When there is abnormal such as overload or overvoltage, in order to prevent the inverter and asynchronous motor from being damaged, stop the inverter or suppress the voltage, the current value.