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Performance RFC mode

128 Unidrive SP Advanced User Guide

www.controltechniques.com Issue Number: 10

Open-loop, Closed-loop vector

With reference to the diagram below, the transient inductance is defined as

σL

= L

+ (L

/ (L

+ L

))

Based on the parameters normally used for the motor equivalent circuit for transient analysis, i.e. L

= L

+ L

, L

= L

+ L

, the transient inductance

is given by

σL

= L

- (L

/ L

)

The transient inductance is used as an intermediate variable to calculate the power factor in open-loop mode. It is used in the vector algorithm, for

cross-coupling compensation and to set the current controller gains in closed-loop vector mode.

Servo

The transient inductance is the phase inductance for a servo motor. This is half the inductance measured from phase to phase. This value is used for

cross-coupling compensation and to set the current controller gains.

This parameter holds the stator inductance of the motor with rated flux. If the motor flux is reduced the value of stator inductance used by the vector

control algorithm is modified using the motor saturation breakpoints (Pr 5.29 and Pr 5.30). Stator inductance (L

) = L

+ L

from the steady state

equivalent circuit. It should be noted that if this parameter is changed from a non-zero value to zero the power factor (Pr 5.10) is automatically set to

0.850. The same applies to the motor map 2 stator inductance (Pr 21.24) and motor map 2 power factor (Pr 21.10).

When this bit is set the drive provides a cross-coupling feed forward voltage as produced by the transient inductance and a frequency based voltage

feed forward term. These voltages improve the transient performance of the current controllers

5.24

Transient inductance (σL

)

Drive modes Open-loop, Closed-loop vector, Servo

Coding