8monitoring functions – Lenze i700 User Manual
Page 257
Lenze · i700 servo inverter · Reference manual · DMS 1.5 EN · 03/2014 · TD05
257
8
Monitoring functions
8.7
Motor phase failure monitoring
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8.7.4
Monitoring with regard to short circuit and earth fault
The motor phases are monitored with regard to short circuit and earth fault by means of a hardware
circuit. If this monitoring function is activated, the i700 servo inverter reports an error and changes
to the "Pulse inhibit" error status. This error can only be reset after an inhibit time of 5 s has elapsed.
The following table lists possible causes of a short-circuit message:
Note!
The dependence on the commutation angle also causes a dependence on the motor type
used:
• The commutation angle and the angle at the shaft (number of pole pairs) of a
synchronous motor are proportional. This makes it possible to predict which shaft
angle is maximally covered in the event of an error.
• There is still a slip between the commutation angle and the angle at the shaft of an
asynchronous motor. This results in a load dependency which makes it impossible to
predict a maximally covered shaft angle in the event of an error.
For some applications (e.g. when a hoist is lowered at non-zero speed) it may happen
that there is no rotating field anymore, but a DC current is flowing. In this case, condition
2 is no longer met.
Cause
Remedies
The is a physical connection between two motor phases. Correct the wiring and remove the short circuit.
A transient current control process causes the phase
currents to increase above the signalling threshold. This
can happen if it is operated at the current limit of the
device and
a) the current controller is set incorrectly or
b) a synchronous motor is operated in the field
weakening range and the current controller feedforward
control in
(or
for axis B) has been
deactivated.
A transient current control process can be triggered, for
instance, if an EtherCAT fault causes a quick stop. In such
a situation, normally some bus cycles pass by until the
error is triggered. During this period, the setpoints
remain frozen which causes an unsteady setpoint profile
and thus a dominant current control process.
Remedy for a):
Set current controller according to alignment
instructions.
Setting and optimising the current controller
Remedy for b):
If a synchronous motor is operated at the limits or within
the field weakening range, activate the current
controller feedforward control in
(or
for
axis B).