E300 Installation and Commissioning Guide
167
Issue Number: 1
8.2.2 Speed control loop gains
8.3 Motor acoustic noise
Following set-up of the drive with the correct motor data and auto tuning section 7.3
on page 133, the drive settings can be further optimized
to overcome motor acoustic noise. This motor instability which results in acoustic noise will also result in limited speed control loop gains.
Table 8-1 Motor parameters, acoustic noise
Speed control loop gains
P Gain parameters I01 (Start), I06 (Run), I11 (Stop)
I Gain parameters I02 (Start), I07 (Run), I12 (Stop)
Speed control loop filter, C09
The speed control loop gains control the response of the speed controller to a change in speed demand. The speed controller includes both a
proportional (P) and integral (I) feed forward term. The drive has three sets of P and I gains from default one for the Start and one for the Travel and
Stop.
Proportional gain
(P)
Start Speed Loop P Gain
(
I01
) and
Run Speed Loop P Gain
(
I06
) and
Stop Speed Loop P Gain
(
I11
)
If the proportional gain has a value and the integral gain is set to zero, there must be a speed error to produce a torque reference. Therefore as the
motor load increases there will be a difference between the speed reference and actual speed. This effect, called regulation, depends on the level
of proportional gain, the higher the gain the smaller the speed error under 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.
Integral gain
(I),
Start Speed Loop I Gain
(
I02
) and
Run Speed Loop I Gain
(
I07
) and
Stop Speed Loop I Gain
(
I12
)
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 by applying a load torque to the motor. Increasing the integral gain to very high values can reduce the system damping giving
overshoot after a transient. For a given integral gain the damping can be improved by increasing the proportional gain.
•
Tuning the speed loop gains involves monitoring the speed feedback from the drive using an oscilloscope connected to one of the Analog
outputs, or using the PC oscilloscope connected over comms, or monitoring the vibration level within the elevator car using an accelerometer.
•
The drive is operated over a travel monitoring the response on the oscilloscope or the accelerometer and identifying any reduced ride quality.
•
The proportional gain (P) should be set-up initially. The value should be increased up to the point where the speed overshoots or vibration is
excessive and then reduced to achieve the required ride comfort level.
•
The integral gain (I) should then be increased up to the point where the speed becomes unstable or vibration occurs and then reduced slightly.
•
It may now be possible to increase the proportional gain slightly further, and the process should be repeated for both the proportional and
integral gains until the system response matches the required ride comfort.
•
The travel during tuning of the speed loop gains should be carried out for both a No-load and Full-load condition
The figure below shows the effect of P proportional and I integral gain adjustments as seen on an oscilloscope as well as the ideal response.
In some systems where low resolution feedback devices are used resulting in quantization, or where there is induced noise present on the position
feedback due to the system wiring and termination, the maximum speed control loop gain settings can be limited. To improve the position feedback
quality a feedback filter is available in
Encoder Feedback Filter
(
C09
) which can in some instances allow for higher speed control loop gains to be
achieved.
Parameter
Setting
Maximum Switching Frequency
(
B13
)
Low switching frequencies < 6 kHz can result in high motor acoustic noise. High switching frequencies > 12 kHz
can result in drive derating.
Recommended = 8 to 12 kHz.
Start Current Loop P Gain
(
I03
)
Run Current Loop P Gain
(
I08
)
High values of current loop P gain (> 150 % of autotune value) can result in motor acoustic noise. Low values of
current control loop gains (< 50 % of autotune value) will result in oscillations and poor ride quality.
Recommended = Autotune values
Start Current Loop Filter
(
I05
)
Run Current Loop Filter
(
I10
)
Used to over come motor acoustic noise and instability due to system induced noise as a result of un-shielded
cables or poor shield and ground terminations.
Recommended = 1.0 to 4.0 ms
Encoder Feedback Filter
(
C09
)
Used to over come motor acoustic noise and instability due to system induced noise as a result of un-shielded
cables or poor shield and ground terminations.
Recommended = 1 to 2 ms
Insufficient proportional
gain
Excessive proportional
gain
Excessive integral gain
Ideal response
Speed demand
Summary of Contents for E300 Series
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