5 Motor control & motor settings
5.11 Setting control loops
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Lenze · i700 servo inverter · reference manual · DMS 3.0 EN · 06/2016 · TD06
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5.11.7 Field weakening operation - synchronous motor (SM)
The control of the i700 servo inverter permits the operation of a synchronous motor outside the
voltage range. If a motor is selected in the »Easy Starter«, the control is automatically
parameterised.
In order to improve the transition from the base speed range to field weakening, we recommend the
activation of the current controller feedforward control via the object 0x2941
(or 0x3141 for axis B).
• The current controller feedforward control is determined via the following parameters:
• Motor stator resistance (0x2C01:2
or 0x3401:2 for axis B)
• Motor stator leakage inductance (0x2C01:3
or 0x3401:3 for axis B)
• e.m.f constant (0x2C03:1
or 0x3403:1 for axis B)
• If a third-party motor is to be operated in the field weakening range, the parameters mentioned
before have to be selected carefully.
The terminal voltage approximately corresponds to the following equation:
Stop!
Operation of synchronous motors outside the voltage range:
If a pulse inhibit is set in the servo inverter, e.g. in the case of controller inhibit or in the
event of an error, the DC bus will load up to the terminal voltage corresponding to the
actual speed (see equation below).
• At high speeds outside the voltage range, the terminal voltage may be higher than the
mains voltage!
• Connect a brake chopper to the DC bus to prevent the DC bus from reaching
impermissibly high voltages!
Equations for calculating the terminal voltage
Axis A Axis B Description Dimension unit
0x2540:1 Rated mains voltage V
0x2C01:4
0x3401:4 Rated motor speed r/min
V
Terminal
Actual speed
Rated mains voltage
Rated motor speed
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