Inverter interference case problem analysis and processing - Database & Sql Blog Articles

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1. How to Identify Inverter Interference Issues Inverter interference typically manifests in the motor’s performance. For instance, the motor may suddenly stop while running, run at inconsistent speeds, or fail to stop even when the stop button is pressed. These symptoms often indicate that the inverter is experiencing interference. It's crucial to identify these issues early to prevent damage and ensure smooth operation. 2. Effective Solutions for Grounding Interference One of the most effective ways to address grounding-related interference is to ensure proper grounding. The grounding terminal should be connected using a third-way grounding method (separate grounding), with the shortest possible wire and a solid connection. Control cables should use shielded wires, with the shielding grounded at the near end and left floating at the far end. Follow the manufacturer’s guidelines for wiring, keeping high-power and low-power lines separated and avoiding parallel routing. Use filters or reactors on the inverter’s input and output, implement shielding measures to reduce electromagnetic induction, and consider enclosing the inverter in a metal box for additional protection. Reducing the carrier frequency can also help minimize interference. If communication functions are used, always opt for twisted pair cables for RS485 connections. 3. Case Study: Grounding Problems in Three-Phase Five-Wire Systems A common issue occurs when an inverter fails to stop after pressing the stop button. Upon inspection, it was found that the inverter’s ground wire was only connected to the transformer’s neutral line, which was not properly grounded. After grounding the transformer’s neutral line, the inverter functioned normally. Many small factories neglect proper grounding, sometimes connecting only the neutral line to the “N” terminal and ignoring the ground wire. Even if shielded cables are used, improper grounding can leave the system vulnerable to interference. Connecting the ground wire directly to earth is a safer alternative, though some users still connect the ground to the neutral line. However, this method poses risks—such as electric shock—if the neutral line is disconnected. This type of interference stems from internal grounding issues within the inverter. 4. External Equipment Interference Example (1) Symptoms: Occasionally, the motor fails to stop. Shield grounding checks out, and reducing the carrier frequency doesn’t resolve the issue. Input and output filters also show no improvement. (2) Diagnosis: The inverter’s power distribution cabinet is located too close to the main power room, where large currents generate strong magnetic fields. These fields interfere with the inverter’s operation. Moving the cabinet away from the power room resolves the issue, indicating external equipment interference. 5. Inverter Interference Affecting External Devices (1) Symptoms: The motor does not start after the inverter is turned on. (2) Diagnosis: The inverter receives a 4-20mA signal from an external transmitter. The display shows 0.00Hz, and the transmitter outputs no current. After adding a 102 capacitor across the transmitter’s output, the system returns to normal. This shows that the signal source was disturbed by the inverter. Using a simple shunt capacitor can effectively solve such issues in real-world engineering scenarios.