SEW inverter maintenance

Introduction to the frequency converter
The main circuit of the frequency converter is the power conversion part that provides voltage-regulated and frequency-modulated power supply to the asynchronous motor. The main circuit of the frequency converter can be roughly divided into two types. The voltage type converts the DC power supply into For AC inverters, the filtering of the DC loop of the inverter is a capacitor. For current-type inverters, which convert the DC of the current source into AC, the DC loop filtering is an inductor. The inverter consists of three parts: a rectifier that converts industrial frequency power into DC power, a [smoothing circuit] that absorbs voltage pulsations generated by the converter and inverter, and an inverter that converts DC power into AC power. . Frequency converter rectifiers have recently used diode converters in large quantities. Frequency converters convert industrial frequency power into DC power. Frequency converters can use two sets of transistor converters to form a reversible converter. Since its power direction is reversible, Regeneration operation is possible. In the smoothing circuit of the frequency converter, in the DC voltage rectified by the rectifier, the frequency converter contains a pulsating voltage that is twice the frequency of the oil power supply. In addition, the pulsating current generated by the inverter also causes the DC voltage to fluctuate. In order to suppress voltage fluctuations, inductors and capacitors are used to absorb the pulsations. Voltage and current). When the capacity of the inverter device is small, if the power supply and the main circuit components have margin, the inverter can omit the inductor and adopt a simple smoothing circuit. The frequency converter inverter is the opposite of the rectifier. The inverter converts DC power into AC power at the required frequency. It uses a switching device to turn on at a determined time, and when the frequency converter is turned off, a three-phase AC output can be obtained. The frequency converter takes a voltage-type inverter as an example for the switching time and voltage waveform. The inverter control circuit is a circuit that provides control signals to the main circuit board that supplies power to asynchronous motors (voltage and frequency are adjustable). It has frequency and voltage calculation circuits, main circuit voltage and current check circuits, and motor speed detection circuits. It consists of a drive circuit that amplifies the control signal of the arithmetic circuit, and a protection circuit for the inverter and motor.
Arithmetic circuit: The inverter calculates and compares external speed, torque and other instructions with the current and voltage signals of the detection circuit to determine the output voltage and frequency of the inverter.
Voltage and current detection circuit: The frequency converter is electrically isolated from the main circuit to detect voltage, current, etc.
Drive circuit: The circuit in which the frequency converter drives the main circuit components. It is isolated from the control circuit to turn on and off the main circuit components.
The frequency converter speed detection circuit takes the signal of the speed detector installed on the asynchronous motor shaft as the speed signal and sends it to the calculation loop. According to the instructions and calculations, the motor can run at the command speed.
Protection circuit: The frequency converter detects the voltage, current, etc. of the main circuit. When overload or overvoltage and other abnormalities occur, in order to prevent the inverter and asynchronous motor from being damaged, the inverter stops working or suppresses the voltage and current values. .
The frequency converter has a power range of up to 100% and is suitable for almost all open-loop drive applications. It can perform frequency conversion speed regulation on non-AC reduction motors.