nverter

Wiring an inverter is simple: follow the wiring diagram! But how do you create that diagram? By understanding the control principles! What are the control principles? You need to know what an inverter is and what it does. If you don’t understand these basics, you won’t learn how to wire an inverter.

An inverter, as the name suggests, is a machine that changes the frequency of three-phase AC power. By altering the frequency of the three-phase AC power applied to a three-phase asynchronous motor, the motor achieves speed control. Therefore, the wiring of an inverter is divided into two parts: the main circuit wiring and the control circuit wiring.

Main Circuit Wiring

The main circuit is the power part, where the three-phase AC power from the grid is connected to the input of the inverter, and the output of the inverter is connected to the three-phase asynchronous motor. The control circuit involves the control wiring for the operator to manage the inverter, similar to the input and output of a PLC. The operator needs to send start, stop signals, and speed signals to the inverter, and the inverter needs to provide status outputs so that the operator can monitor the inverter’s status in real-time.

As shown in the figure, the main circuit wiring is straightforward. Generally, the inverter’s input is denoted by L1, L2, L3, and the output by U, V, W. It’s crucial to consult the manual, as reversing the input and output can have severe consequences. The red circle in the figure indicates the inverter’s DC bus section, which is complex and not necessary for general applications. When external braking resistors or DC reactors are needed, follow the programming manual’s instructions, usually involving removing or installing certain jumpers.

Control Circuit Wiring

The control circuit is similar to the input and output wiring of a PLC. Start and stop signals are digital, while speed signals are analog. The inverter’s input also comes in NPN and PNP types, just like a PLC, achieved through different common points. Many inverters, especially economical ones, support only one type, with PNP being more common.

The figure shows the wiring for a Mitsubishi inverter. The top part is the start signal, and the bottom part is the inverter’s digital output signal.

Conclusion

Regardless of the automation product’s wiring, it’s essential to understand the principles and consult the manual. The wiring principles for automation products are the same, involving digital and analog signals. The interaction of signals between different automation products is similar to the input and output of a PLC. Only by mastering the principles can you achieve a comprehensive understanding. Otherwise, you’ll only learn one product at a time, and you’ll never truly master it.