70
Digitax ST User Guide
Issue: 5
Current loop gains (Pr 0.38 {4.13} / Pr 0.39 {4.14})
The current loop gains proportional (Kp) and integral (Ki) gains control the response of the current loop to a change in current (torque) demand. The
default values give satisfactory operation with most motors. However, for optimal performance in dynamic applications it may be necessary to
change the gains to improve the performance. The proportional gain (Pr
4.13
) is the most critical value in controlling the performance. The values
for the current loop gains can be calculated by one of the following:
•
During a stationary or rotating autotune (see
Autotune Pr
0.40
, earlier in this table) the drive measures the stator resistance (Pr
5.17
) and
transient inductance (Pr
5.24
) of the motor and calculates the current loop gains.
•
By setting Pr
0.40
to 6 the drive will calculate the current loop gains from the values of stator resistance (Pr
5.17
) and transient inductance
(Pr
5.24
) set in the drive.
This will give a step response with minimum overshoot after a step change of current reference. The proportional gain can be increased by a factor
of 1.5 giving a similar increase in bandwidth; however, this gives a step response with approximately 12.5 % overshoot. The equation for the integral
gain gives a conservative value. In some applications where it is necessary for the reference frame used by the drive to dynamically follow the flux
very closely (i.e. high speed closed-loop induction motor applications) the integral gain may need to have a significantly higher value.
Summary of Contents for Digitax ST
Page 1: ...User Guide AC variable speed drive for servo motors Part Number 0475 0001 05 Issue 5 ...
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Page 210: ...0475 0001 05 ...
