Solution of the frequency inverter reports output phase failure during the operation

Fault Name:

The frequency inverter reports output phase failure during the operation.

Fault Symptom:

The frequency inverter reports output phase failure during the operation (Err2/E.oLF)

Causes:

The motor loses phase; 

The motor wiring is not well connected; 

The three-phase output voltage of the inverter is unbalanced; 

The three-phase output current of the inverter is unbalanced.

Solution:

Use a multimeter to measure the three-phase stator resistance of the motor and see if it’s consistent, after confirmation, replace or repair the motor; 

If the motor three-phase stator resistance is consistent, then disconnect the inverter output cable, check the three-phase line cable (connecting motor) resistance value to ensure the reliable connection of output cable; 

If there is no abnormality at the output side of the inverter, the motor can be disconnected; the inverter runs at no load to measure the three-phase output voltage; if it is not balanced, check the hardware driving circuit. And IGBT, if there is a fault, then replace or repair it; 

When the frequency inverter with motor three-phase output current is unbalanced, detect the current detection abnormal phase and replace or repair it. Hall models can be used to determine the abnormal part.

Analysis: 

At present, the universal frequency inverter software is judged by the current detection signal. Based on the theory that the sum of three-phase currents is zero, the same applies when there is a phase loss. Based on this theoretical software to determine the phase failure, that is, the maximum phase current is much greater than the minimum phase current and the maximum phase output current is greater than 10% of the motor rated current (different software will have a slight difference). Taking into account the situation of the motor oscillation, etc., in order to avoid misjudgment of the software will make multiple cycle sampling judgments; therefore, the output phase loss failure will have a certain delay, generally within 3 seconds.

Cautions:

The site needs to avoid the excessive crossover between the frequency inverter and motor, the inverter motor parameters and the actual motor does not match the situation; 

the output frequency is too low (less than 1Hz, different software will be different) and it does not report the output phase loss failure; 

With a synchronous motor phase loss due to low output current at low speed no-load under this condition that cannot reach the condition of the lack of phase, in this case, certainly determine not the output phase.