Current limit C0599 for motor phase failure monitoring (LP1)

Question:

What are the consequences of the C0599 input parameter 'current limit LP1' of the motor phase failure monitoring?

Answer:

The failure / the interruption of a motor phase (U, V, W) is detected from the fact that the current flow of each single motor phase is examined by means of the settable current threshold (C0599).
The per cent value under C0599 refers to the fixed device rated current (not to the settable maximum current C0022).

The set LP1-error response is released under following conditions:

1. The effective current of one motor phase 'U' or 'V' or 'W' is below the settable current threshold (C0599 x device rated current) AND the motor rotates mechanically by more than 90 ° (motor encoder).
2. The effective current is in two motor phases simultaneously below the settable current threshold (C0599 x device rated current).

By setting the per cent value in code C0599 the sensibility of the motor phase failure detection can quasi be set. The higher the set per cent value, the higher the sensibility.
In the inverter the current is measured in two wires, in the third one it is calculated. Therefore, the monitoring works for all three motor phases.
Due to the possible risks for the connected motor, 'TRIP' (C0597 = 0) is to be preferred to 'Warning', as it leads to controller inhibit.

Note:
When synchronous motors are operated the activation can lead to undesired triggering, as in this case - in contrast to the asynchronous motor - a magnetising current does not have to flow. Therefore, under normal operating conditions the synchronous motor can have states with very low currents in the motor cables. It is possible that the LP1 monitoring is not activated.

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