Soft faults in frequency converters are very common, and they are one of the most frequent types of faults encountered during the operation of various frequency converters. So how can we reduce the occurrence of soft faults in frequency converters? This is a question of great concern to all frequency converter manufacturers and users. The following will provide a detailed explanation.
Methods to reduce inverter soft faults include: 1. Detecting overvoltage and undervoltage in the inverter; 2. Detecting overcurrent, which is the most frequent alarm phenomenon in inverters.
Overvoltage alarms typically occur during shutdown, primarily due to insufficient deceleration time or problems with the braking resistor and braking unit. Undervoltage is another common issue encountered during operation. This is mainly due to low main circuit voltage (below 200V for 220V series, below 400V for 380V series). The main causes include: damage to one circuit of the rectifier bridge or malfunction of any of the three thyristor circuits; a damaged main circuit contactor causing DC bus voltage loss across the charging resistor; and a faulty voltage detection circuit.
The overcurrent phenomenon mainly manifests as follows:
(1) The circuit breaker trips immediately upon restarting and accelerating. This indicates a severe overcurrent. The main causes include: load short circuit, mechanical jamming, inverter module damage, and insufficient motor torque.
(2) The circuit trips immediately upon power-on. This phenomenon is generally not resetting. The main reasons are: the module is faulty, the drive circuit is faulty, or the current detection circuit is faulty.
(3) The circuit breaker does not trip immediately upon restart but only during acceleration. The main reasons are: the acceleration time is set too short, the current limit is set too low, and the torque compensation (V/F) is set too high.
