Lenze i700 - Limits of the Motor Phase Failure Monitoring

Lenze · i700 servo inverter · reference manual · DMS 3.0 EN · 06/2016 · TD06 271
8 Monitoring functions
8.7 Motor phase failure monitoring
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8.7.1 Limits of the motor phase failure monitoring
The motor phase failure monitoring can be activated for both synchronous and asynchronous
motors. However, it is possible that a current flow cannot be detected for sure in the case of certain
operating states of synchronous motors that are connected correctly. Hence, a fault is triggered. The
following table provides an overview:
Special case: Operation in generator mode (e.g. hoist)
The motor phase failure monitoring may trigger a fault message in an operation in generator mode
if the asynchronous motor applied for this purpose reaches the following working point:
• The hoist moves downwards, i.e. the motor is in generator mode.
• The slip frequency equals the field frequency in terms of amount. Both frequencies mutually
neutralise themselves due to their opposite effective directions.
Subindex 4: Motor phase failure 2: Response
Monitoring 2 (prior to operation):
Response during activation
Selection list (Lenze setting printed in bold)
0 No response
1Fault
2 Warning
 Write access  CINH  OSC  P  RX  TX UNSIGNED_8
Operating status Synchronous motor Async. motor
Check of the motor phases prior to operation 
Check of the motor phases during operation
I
q
< current threshold value at standstill 
when motor is rotating 
I
q
≥ current threshold value at standstill 
when motor is rotating 
Field weakening when motor is rotating 
 Phase failure is detected for sure
 The monitoring function may be activated without a fault pending.
I
q
Torque-forming current component
 Note!
Monitoring during operation serves especially for applications which are operated with
constant load and speed. In all other cases, transient processes or unfavourable
operating points can cause maloperation.