Overcurrent protection and processing method for inverters - News - Global IC Trade Starts Here Free Products

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1. Overcurrent Protection Function

Inverters are equipped with overcurrent protection to prevent damage caused by sudden surges in current that exceed the device’s allowable limits. This is especially important because inverters have limited overload capacity, making overcurrent protection a critical feature. The technology has evolved significantly over time, ensuring more reliable performance.

(1) Causes of Overcurrent

Overcurrent can occur under various conditions:

1. Operational Overcurrent: This happens when the motor or drive system experiences unexpected current spikes during operation. Common reasons include:

• The motor encounters an impact load or the drive mechanism becomes "stuck," causing a sudden increase in current.
• A short circuit occurs on the inverter's output side, such as between the terminals and the motor, or within the motor itself.
• Internal issues within the inverter, like improper switching between devices in the same bridge arm, leading to a "short circuit" situation.

For example, high ambient temperatures or aging components may cause parameter drift in the inverter. This could result in one device being turned on while the other remains off during the switching process, creating a direct path between the DC supply’s positive and negative terminals—leading to a dangerous short circuit.

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 rapid rise in speed. The motor’s rotor may not be able to match the synchronous speed, resulting in excessive current draw.

3. Overcurrent During Deceleration

Similarly, if the deceleration time is too short, the motor’s rotor may continue spinning at a high speed due to the load’s inertia. This causes the rotor to cut through magnetic lines rapidly, generating an overcurrent condition.

(2) Troubleshooting and Solutions

When overcurrent occurs, it's important to identify the root cause and take corrective actions:

1. If the inverter trips immediately upon starting, check for mechanical issues such as a stuck working machine, short circuits on the load side (using a megger), or damaged power modules. Also, ensure the motor has sufficient starting torque to drive the system.

2. If the inverter starts without tripping but trips during operation, consider the following:

• Short acceleration time: Increase the acceleration duration to allow smoother speed ramp-up.
• Short deceleration time: Extend the deceleration period to avoid sudden drops in speed.
• Excessive torque compensation (U/F ratio): Adjust the setting to reduce no-load current at low frequencies.
• Improperly set electronic thermal relay: Ensure the operating current threshold is set correctly to avoid false trips.

By understanding these causes and implementing appropriate adjustments, users can effectively manage and prevent overcurrent situations in their inverter systems.