The main circuit of the inverter is composed of Reynolds

When it comes to inverter repair, it's not enough to understand the above fundamental circuits, but also to understand the following primary circuits. The main circuit is mainly composed of rectifier circuit, current limiting circuit, filter circuit, braking circuit, inverter circuit and detection and sampling circuit.

The main circuit of the inverter is composed of Reynolds

The main circuit of the inverter is composed of Reynolds

1) Drive circuit

The drive circuit is to isolate and expand the six PWM signals generated by the CPU in the main control circuit through optical resistance, and then provide the driving signals as the converter equipment (inverter module) of the inverter circuit.

The requirements for the drive circuit vary depending on the converter equipment. At the same time, some developers have developed a number of special drive modules suitable for various converter devices. Some brands and models of inverters directly use special drive modules. However, most of the inverters use drive circuits. From the perspective of repair, here is a description of the more typical drive circuits. The drive circuit consists of a barrier expansion circuit, a drive expansion circuit and a power supply for the drive circuit. The three upside arm drive circuits are three independent drive power circuits, and the three downside arm drive circuits are one common drive power circuit.

2) Maintain the circuit

When there is an abnormality in the inverter, in order to minimize the loss of the inverter due to the abnormality, or even reduce it to zero. Each brand of inverter pays great attention to maintenance function, and all try to add maintenance function to improve the effectiveness of maintenance function.

In the field of inverter maintenance function, manufacturers can be said to do their best to make a good article. In this way, the diversity and complexity of the inverter maintenance circuit are formed. There is a conventional detection and maintenance circuit, and the software summarizes the maintenance function. Some inverters' drive circuit modules, intelligent power modules, rectifier inverter combination modules, etc., all have internal maintenance functions. It is composed of three parts: current sampling, signal blocking expansion, and signal expansion output.

3) Switching power supply circuit

The switching power supply circuit provides low-voltage power to the operation panel, main control board, drive circuit and fan circuit. The DC high-voltage P terminal is added to the primary end of the high-frequency pulse transformer, and the switch adjustment tube is connected in series to the other primary end of the pulse transformer, and then connected to the DC high-voltage N terminal. The switch tube is periodically turned on and cut off, so that the primary DC voltage is replaced by a rectangular wave. It is coupled to the secondary stage by the pulse transformer, and then rectified and filtered to obtain the corresponding DC output voltage. It also samples and compares the output voltage, and controls the pulse width adjustment circuit to change the pulse width to make the output voltage stable.

4) Communication circuit on the main control board

When the inverter is controlled by a programmable (PLC) or a higher-level computer, human-machine interface, etc., signals must be transmitted to each other through the communication interface. When the frequency device communicates, the two-wire RS485 interface is generally selected. The same is true for Siemens drives. The separation of two wires is used to transmit and receive signals. Before the inverter receives the signal and transmits the signal, these two signals pass through the integrated circuits such as buffer A1701 and 75176B to ensure good communication. Therefore, the communication interface circuit on the main control board of the inverter mainly refers to this part of the circuit, as well as the anti-interference circuit of the signal.

5) External control circuit

The external control circuit of the inverter mainly refers to the frequency setting voltage input, frequency setting current input, forward rotation, rotation, jog and stop operation control, and multi-speed control. The input signal of the frequency-setting voltage (current) enters the CPU through the A/D conversion circuit in the inverter. Other controls are passed to the CPU via an opto-coupling block in the input circuitry of the inverter.

The main circuit of the inverter is composed of Reynolds

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