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156 HVAC Drive H300
Issue Number: 3
Speed Loop Gains (Pr 00.014 {03.010}, Pr 00.015 {03.011}, Pr 00.016 {03.012})
The speed loop gains control the response of the speed controller to a
change in speed demand. The speed controller includes proportional
(Kp) and integral (Ki) feed forward terms, and a differential (Kd) feedback
term.
Speed Controller Proportional Gain (Kp), Pr 00.014 {03.010}
If the proportional gain has a value and the integral gain is set to zero the
controller will only have a proportional term, and there must be a speed
error to produce a torque reference. Therefore as the motor load
increases there will be a difference between the reference and actual
speeds. This effect, called regulation, depends on the level of the
proportional gain, the higher the gain the smaller the speed error for a
given load. If the proportional gain is too high either the acoustic noise
produced by speed feedback quantization becomes unacceptable, or the
stability limit is reached.
Speed Controller Integral Gain (Ki), Pr 00.015 {03.011}
The integral gain is provided to prevent speed regulation. The error is
accumulated over a period of time and used to produce the necessary
torque demand without any speed error. Increasing the integral gain
reduces the time taken for the speed to reach the correct level and
increases the stiffness of the system, i.e. it reduces the positional
displacement produced by applying a load torque to the motor.
Unfortunately increasing the integral gain also reduces the system
damping giving overshoot after a transient. For a given integral gain the
damping can be improved by increasing the proportional gain. A
compromise must be reached where the system response, stiffness and
damping are all adequate for the application. For RFC-A Sensorless
mode, it is unlikely that the integral gain can be increased much above
0.50.
Differential Gain (Kd), Pr 00.016 {03.012}
The differential gain is provided in the feedback of the speed controller to
give additional damping. The differential term is implemented in a way
that does not introduce excessive noise normally associated with this
type of function. Increasing the differential term reduces the overshoot
produced by under-damping, however, for most applications the
proportional and integral gains alone are sufficient.
gain [
00.014]
Excessive integral gain
[
00.015
]
Ideal response
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