The quality of the power supply is critical, especially for inverter units.
Undervoltage
Low voltage can increase current and lead to inverter protection or inability to start.
Overvoltage
Excessive voltage can trigger DC bus protection and stop the unit.
Transient phenomena
Short voltage fluctuations can leave intermittent faults that are only visible in the history.
Diagnosis
Voltage is measured under load and, if necessary, a power quality recorder is used.