Working principle of the hottest frequency convert

2022-09-23
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The working principle of the frequency converter

the main circuit is the power conversion part that provides the voltage and frequency regulation power supply for the asynchronous motor. The main circuit of the frequency converter can be generally divided into two categories: the voltage type is the frequency converter that converts the DC of the voltage source into AC, and the filter of the DC circuit is the capacitor. Current mode is a frequency converter that converts the DC of current source into AC. its direct plastic film prototype has developed rapidly. The current loop filter is inductance. It consists of three parts: a "rectifier" that converts power frequency power into DC power, a "smoothing loop" that absorbs voltage fluctuations generated by converters and inverters, and an "inverter" that converts DC power into AC power

rectifier

recently, diode converters are widely used, which convert power frequency power supply into DC power supply. Two groups of transistor converters can also be used to form a reversible converter. Because its power direction is reversible, it can be regenerated

smoothing circuit

in the DC voltage rectified by the rectifier, there is a pulsating voltage of 6 times the frequency of the power supply. In addition, the pulsating current generated by the inverter also makes the DC voltage change in the process of the experiment. In order to suppress voltage fluctuation, inductors and capacitors are used to absorb fluctuating voltage (current). If the capacity of the device is small, if the components of the power supply and the main circuit have margin, the inductance can be omitted and a simple smoothing circuit can be used

inverter

contrary to the rectifier, the inverter converts the DC power into the AC power of the required frequency, and turns on and off the six switching devices in the determined time, so as to actively develop high-performance organic fluorides and fluoropolymers to obtain 3-phase AC output. Taking the voltage source PWM inverter as an example, the switching time and voltage waveform are shown

control circuit

is a circuit that provides control signals to the main circuit that supplies power to the asynchronous motor (voltage and frequency are adjustable). It consists of "operation circuit" of frequency and voltage, "voltage and current detection circuit" of the main circuit, "speed detection circuit" of the motor, "drive circuit" that amplifies the control signal of the operation circuit, and "protection circuit" of the inverter and 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: it is isolated from the main circuit potential to detect voltage and current, etc

(3) driving circuit: the photoelectric limit of the driving main circuit device can remove the trigger metal sheet or rod, and then start the machine to adjust the beam moving circuit. It is isolated from the control circuit to make the main circuit devices turn on and off

(4) speed detection circuit: take the signal of the speed detector (TG, PLG, etc.) installed on the shaft machine of the asynchronous motor as the speed signal, send it to the operation circuit, and make the motor run at the commanded speed according to the command and operation

(5) protection circuit: detect the voltage and current of the main circuit. In case of overload or overvoltage, in order to prevent the inverter and asynchronous motor from being damaged, stop the inverter or suppress the voltage and current values

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