Overview
Inverters are widely used in motor and electrical control systems. Aside from local panel operation, inverters provide auxiliary terminals for remote or centralized control. These control circuits operate via wires connected to the inverter's auxiliary terminals. They are flexible and commonly used in industrial control applications.
Although auxiliary terminal control has advantages, improper wiring of control circuits can adversely affect inverter operation or cause faults. Based on practical experience, the following summarizes six wiring precautions for inverter control circuits.
Six Precautions
- Keep control wiring separate from main power cables. This reduces the risk that harmonic components from the inverter main circuit will interfere with the control circuit.
- Fault signal terminals and multifunction contact outputs may drive high-voltage AC contactors or relays. Route these connections separately from other control circuit terminals and contacts to avoid high-voltage breakdowns.
- To prevent interference-induced false operations, use shielded cable or twisted pair with strong anti-interference performance for low-level control circuits, such as wiring from sensors under PID control.
- Use 50 m as a reference for control wire length (in some cases 100 m; this depends on conductor cross-section, material, and signal amplitude). When wiring distance exceeds this reference, use repeater circuits or relays to condition or amplify the signal.
- When crimping control wires, pay particular attention to the polarity of analog signals to prevent reversed polarity that could damage the inverter's auxiliary control electronics.
- When the inverter is energized, do not use a digital multimeter's continuity/beeper function to test control circuit continuity, because this range can output a higher voltage than other ranges. The meter can feed voltage through the probes into the inverter control terminals and cause unintended operations.
