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Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

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1. Overcurrent Protection Function

In an inverter system, the primary concern of overcurrent protection is when the peak current exceeds the inverter's allowable limit abruptly. Since inverters have limited overload capacity, overcurrent protection is a critical feature that has evolved significantly over time.

(1) Causes of Overcurrent

Overcurrent can occur during normal operation, particularly when the drive system experiences unexpected issues. The main causes include:

• Motor encountering an impact load or mechanical jamming, leading to a sudden increase in current.
• Short circuits on the inverter’s output side, such as between the terminals and the motor or within the motor itself.
• Malfunction of the inverter components, like both devices in the same bridge arm being turned on simultaneously due to faulty switching, causing a “short circuit” between DC bus terminals.

For example, high ambient temperatures or aging of the inverter module can alter its internal parameters. This may result in one device turning on while the other remains off, creating a direct short between the positive and negative DC rails.

2. Overcurrent During Acceleration

If the load has high inertia and the acceleration time is set too short, the inverter may experience overcurrent. This happens because the inverter increases speed too quickly, while the motor rotor cannot keep up with the rapid change in synchronous speed, resulting in excessive current draw.

3. Overcurrent During Deceleration

Similarly, if the deceleration time is too short, the motor rotor may still be spinning at a high speed due to the load's inertia, even though the synchronous speed has dropped rapidly. This mismatch causes an overcurrent condition as the rotor windings cut through magnetic lines at a higher rate than expected.

(2) Troubleshooting Methods

When the inverter trips immediately upon starting, it could indicate serious overcurrent issues. Key checks include:

• Checking if the connected machinery is stuck or not operating smoothly.
• Verifying the load side for any short circuits using a megohmmeter.
• Inspecting the inverter power module for damage.
• Ensuring the motor has sufficient starting torque to drive the system properly.

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

• Extending the acceleration time to reduce the rate of speed increase.
• Increasing the deceleration time to avoid sudden drops in speed.
• Adjusting the torque compensation (U/F ratio) to prevent excessive no-load current at low frequencies.
• Reviewing the electronic thermal relay settings to ensure the operating current is appropriately set to avoid false tripping.