Inverter overcurrent processing method - Solutions - Huaqiang Electronic Network

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Overcurrent protection in an inverter is essential because it helps prevent damage caused by excessive current that exceeds the device's safe operating limits. Inverters are sensitive to overcurrent conditions, especially since they have limited overload capacity. This makes overcurrent protection a critical part of inverter design and operation.

1. Causes of Overcurrent

1. Overcurrent during normal operation: This typically occurs when the motor or drive system experiences abnormal conditions. Common causes include:

• The motor encounters an impact load or the mechanical system becomes jammed, causing a sudden surge in current.
• A short circuit occurs on the output side of the inverter, such as between the inverter terminals and the motor, or within the motor itself.
• The inverter itself may malfunction, such as when two devices in the same bridge arm fail to switch properly. For example, due to high ambient temperature or aging components, one device might remain on while the other is off, leading to a "short-circuit" between the DC bus positive and negative terminals.

2. Overcurrent during acceleration: If the load has high inertia and the acceleration time is too short, the inverter may struggle to keep up with the required speed increase. This can cause the motor’s rotor to lag behind the synchronous speed, resulting in a sudden rise in current.

3. Overcurrent during deceleration: A similar issue arises when the deceleration time is set too short. The motor’s rotor, due to the load’s inertia, continues to rotate at a high speed even as the synchronous speed drops rapidly. This mismatch can lead to excessive induced currents and trigger an overcurrent condition.

2. Troubleshooting and Solutions

1. Overcurrent at start-up: If the inverter trips immediately upon starting, consider the following:

• Is the mechanical system stuck or jammed?
• Is there a short circuit on the load side? Use a megohmmeter to check for grounding issues.
• Is the inverter power module damaged? Inspect for signs of overheating or physical damage.
• Is the motor’s starting torque too low, preventing the system from turning?

2. Overcurrent during operation: If the inverter doesn’t trip at start-up but trips later, check the following:

• Is the acceleration time too short? Extend the acceleration time to allow smoother speed increases.
• Is the deceleration time too short? Lengthen the deceleration time to avoid sudden speed reductions.
• Is the torque compensation (U/F ratio) set too high? This can cause excessive no-load current at low frequencies.
• Is the electronic thermal relay misconfigured? Ensure the operating current setting is appropriate to avoid false tripping.

In summary, overcurrent in inverters can be caused by various factors ranging from mechanical issues to improper parameter settings. Understanding these causes and implementing proper troubleshooting steps is key to maintaining reliable inverter performance and protecting connected equipment from damage.