As the absolute main force in the field of electric control, the frequency converter can be said to be loved by thousands. Those who are familiar with the inverter know that while the inverter provides panel operation mode, it also provides auxiliary terminal (or external terminal) control mode that is convenient for remote and centralized control. This form of control loop is operated by wires pressed into the auxiliary control terminals of the inverter. Its powerful and flexible functions are the first choice for inverter control.

Although the auxiliary control method of the inverter has many advantages, if the wiring of the control circuit is not reasonable, it will often have an adverse effect on the normal operation of the inverter and even cause unnecessary failures. Today, based on my own work experience, I have summarized six taboos about inverter control circuit wiring:

1. The wires distributed in the inverter control loop should be separated from the main circuit cable (power line), so as to avoid the harmonic interference components in the inverter main loop from polluting the inverter control loop;

2. Due to the inverter's fault signal and multi-function contact output signal terminals, it is possible to drive high-voltage AC contactor/relay, so its wiring should be separated from the terminals or contacts of other control circuits to avoid high-voltage breakdown failure;

3. In order to prevent the malfunction caused by the interference signal, the low-power control circuit of the inverter (such as the wire used for the sensor under the PID control function) should be selected when wiring. The shielded wire or the twisted wire with strong anti-interference ability;

4. For the length of the wire of the inverter control loop, the reference point is usually 50m (in some cases, the value is 100m, which is mainly related to the cross-section of the wire used, the material, the strength of the signal, etc.). Use a relay circuit or relay to amplify the signal;

5. When crimping the control circuit wire of the inverter, pay special attention to the polarity of the analog signal to prevent the reverse polarity from damaging the auxiliary control electronic circuit of the inverter;

6. When the inverter is powered on, do not use the digital multimeter with a buzzer function file (the output voltage of this gear is the highest compared to other gears) to measure the on/off of the control loop to prevent the power in the digital multimeter The test leads are transmitted to the control terminals of the inverter, causing malfunctions!