PCB Technical - Inverter circuit board repair skills

Inverter circuit board repair skills

Main circuit of general-purpose inverter in PCBA board
At present, domestic inverters on the market are mainly low-voltage general-purpose inverters. For the convenience of the following description, the main circuit structure of general-purpose inverters is briefly introduced. The inverter structure is divided into AC-AC inverter and AC-DC- AC frequency converters are divided into main voltage source type frequency converters and current source type frequency converters from the nature of frequency conversion. At present, the domestically produced frequency converters are mainly voltage source type AC-DC-AC frequency converters. The main circuit is mainly composed of rectifier circuit and filter. The circuit, inverter circuit and braking unit are composed of several parts. Among them, IGBT (Insulated Gate Bipolar Transistor) constitutes the main hardware of the inverter. The functions of each part of the circuit are briefly described as follows:

(1) Rectifier circuit

A three-phase bridge full-wave rectifier circuit composed of VD1~VD6 rectifies three-phase alternating current into direct current.

(2) Filter circuit

The DC voltage output by the rectifier circuit is a pulsating DC voltage, so a filter circuit is needed to filter out voltage ripples, and it also plays a role in energy storage in the rectifier circuit and the inverter circuit.

(3) Inverter circuit

The inverter circuit composed of switch tubes V1~V6 converts the DC voltage into three-phase frequency and adjustable voltage AC to drive the three-phase motor, which is the key link for the inverter to achieve frequency conversion.

(4) Current limiting circuit

It is composed of a current-limiting resistor R and a switch K. Since the voltage at the filter capacitor terminal is zero at the moment of power-on, the capacitor charging current is relatively large at the moment of power-on. Excessive current may damage the rectifier circuit. The current resistance is connected in series to the DC loop, and when the capacitor is charged for a certain period of time, the resistance is short-circuited through the switch K.

(5) Brake circuit

is composed of a braking resistor RB and a switch tube VB. The main function is to consume the energy fed back by the motor and avoid excessive pumping voltage from damaging the inverter. According to the different power levels, the Convo Universal G/P series inverters choose IGBTs of different brands such as Opec, Mitsubishi, Toshiba, etc. The main circuit of the inverter power is below 18.5kW. The main circuit mainly adopts integrated rectification and inverse The transformer, brake circuit and temperature detection are integrated into a seven-unit module structure. The models of 22kW and above adopt a rectifier module and a three-way two-unit inverter module.
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