Inverter wiring specification - Solutions - Huaqiang Electronic Network

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When working with inverters and analog signals, it's crucial to separate the signal lines from power lines. This is especially important when using analog control for remote operation of the inverter. To minimize interference from the inverter and other equipment, ensure that the signal lines are kept at least 30cm away from the main circuit and control loop of the inverter. Even inside the control cabinet, this separation should be maintained. The distance between the signal line and the inverter should not exceed 50 meters. Signal and power lines should be routed through separate metal conduits or metal hoses. If the signal cable connecting the PLC and inverter is not placed in a metal conduit, it may be highly susceptible to electromagnetic interference. Since there is no built-in reactor, the input and output stages of the inverter can generate strong interference. Therefore, the metal conduit or hose for the signal line should extend all the way to the inverter’s control terminal to ensure complete isolation from the power lines. 1) For analog control signal lines, use double-stranded shielded cables with a cross-sectional area of 0.75mm². When stripping the cable, keep it as short as possible (5–7mm), and wrap the shielded part with insulating tape to prevent it from touching other components and causing interference. 2) To improve wiring simplicity and reliability, it's recommended to use crimping terminals on the signal lines. Inverter operation and parameter settings: Inverters have numerous parameters, each with specific ranges. Improper settings can lead to malfunction. Common control modes include speed control, torque control, and PID control. After selecting the control method, static or dynamic identification is usually required based on the desired accuracy. The minimum operating frequency refers to the lowest motor speed. At low speeds, the motor's cooling performance is poor, which can lead to overheating if operated for long periods. Additionally, the current in the cable increases at low speeds, potentially causing the cable to overheat. The maximum operating frequency typically reaches 60Hz, with some models going up to 400Hz. High frequencies cause the motor to run at high speeds, which can be problematic for standard motors. Bearings may not withstand prolonged high-speed operation, and the rotor must be able to handle the resulting centrifugal forces. Carrier frequency affects harmonic distortion, motor heating, and cable temperature. Higher carrier frequencies increase harmonics, which can impact performance depending on the cable length. Motor parameters such as power, current, voltage, speed, and maximum frequency should be set according to the motor nameplate data. These values are essential for proper inverter operation. Frequency hopping is used to avoid resonance at certain frequencies, particularly in systems with high mechanical inertia. When controlling compressors, it's important to avoid surge points. Common fault analysis: 1) Overcurrent faults can occur during acceleration, deceleration, or constant speed. Causes may include short acceleration/deceleration times, sudden load changes, uneven load distribution, or output short circuits. Solutions include extending acceleration time, reducing load fluctuations, adding energy dissipation elements, and checking the wiring. If the issue persists, the inverter may need replacement. 2) Overload faults can affect either the inverter or the motor. They may result from short acceleration times, low grid voltage, or excessive load. Extending acceleration and braking times, checking the grid voltage, and inspecting the load distribution can help. If the motor or inverter is undersized for the load, a higher-power unit may be required. Poor mechanical lubrication can also cause overload, requiring system inspection. 3) Undervoltage indicates an issue with the inverter’s power input. Before running the system, check the power supply to ensure stability.