1. Power supply voltage phase imbalance tolerance
Mitsubishi inverter's input power supply voltage phase imbalance tolerance is ±3%.
If the phase imbalance exceeds ±3%, the inverter life may be shortened or may get broken.

2. Phenomena observed when power supply phase imbalance is present
When the inverter's input power supply voltage phase imbalance occurs, the inverter's input current may get greatly imbalanced.
In the worst case, the current does not flow for one phase only.
This may happen when the inverter operates the motor under a light load or at a low speed.
When the current flowing through the load is small, the smoothing capacitor's terminal voltage drops too slowly and no input current flows in the phase with the lowest input power supply voltage.

3. Countermeasure against power supply phase imbalance
By inserting a power factor improving AC reactor into the inverter power supply input side, the current change rate is reduced and the phases are balanced.