Lenze 8400 - Manual (Page 216)

5 Motor control (MCTRL)
5.8 Sensorless control for synchronous motors (SLPSM)
216
Lenze · 8400 protec HighLine · Reference manual · DMS 3.0 EN · 03/2013 · TD05
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5.8.6 Field weakening for synchronous motors
[5-17] Voltage/speed characteristic with switched-on field weakening
[5-18] Calculation of the maximally reachable speed with switched-on field weakening

Note!
In the Lenze setting, the field weakening for synchronous motors is activated in
C00079/4 .
• If a high energy efficiency is required, keep the field weakening switched off or restrict
the field weakening operation via C00938 .

Stop!
In the field weakening operation, a current is injected into the synchronous motor even
in idle state which can rise to maximum current ( C00022 ).
Ensure that this no-load current does not cause the motor to be heated impermissibly!
• We recommend using a temperature feedback via PTC or thermal contact.  Motor
temperature monitoring (PTC) ( 285)
 Armature control range
 Field weakening range
• When field weakening is switched on, the motor
magnetising current is increased from 0 A to the maximally
effective magnetising current via an internal control loop
when the voltage limit is reached.
• As a result, a higher speed can be reached at the same
motor voltage or DC-bus voltage.
n Œ 
U
motor
n
max
n
nenn_mot
800V
2 U
nenn_mot
⋅
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