Digitax HD M753 Control User Guide
77
Issue Number: 3
8 Optimization
This chapter takes the user through methods of optimizing the drive set-up and maximize the performance. The auto-tuning features of the drive
simplify the optimization tasks.
8.1
Motor map parameters
8.1.1
RFC-S mode
Permanent magnet motor with Position feedback
Pr 00.046 {05.007}
Rated Current
Defines the maximum motor continuous current
The motor rated current parameter must be set to the maximum continuous current of the motor. The motor rated current is used in the following:
•
Current limits (see section 8.2
on page 92, for more information)
•
Motor thermal overload protection (see section 8.3
on page 92, for more information)
Pr 00.042 {05.011}
Number Of Motor Poles
Defines the number of motor poles
The number of motor poles parameter defines the number of electrical revolutions in one whole mechanical revolution of the motor. This parameter must be
set correctly for the control algorithms to operate correctly. When Pr
00.042
is set to "Automatic" the number of poles is 6.
Pr 00.040 {05.012}
Autotune
There are four autotune tests available in RFC-S mode, a stationary autotune, a rotating autotune, mechanical load measurement tests to measure load
dependent parameters.
•
Stationary Autotune
The stationary autotune can be used when the motor is loaded and it is not possible uncouple the load from motor shaft. This test can be used to measure all
the necessary parameters for basic control. During the stationary autotune, a test is performed to locate the flux axis of the motor. However this test may not
be able to calculate such an accurate value for the
Position Feedback Phase Angle
(00.043) as compared to rotating autotune. A stationary test is performed
to measure
Stator Resistance
(05.017),
Ld
(05.024),
Maximum Deadtime Compensation
(05.059),
Current At Maximum Deadtime Compensation
(05.060),
No Load Lq
(05.072). If
Enable Stator Compensation
(05.049) = 1 then
Stator Base Temperature
(05.048) is made equal to
Stator Temperature
(05.046).
The
Stator Resistance
(05.017) and the
Ld
(05.024) are then used to set up
Current controller Kp Gain
(00.038) and
Current Controller Ki Gain
(00.039).
If sensorless mode is not selected then
Position Feedback Phase Angle
(00.043) is set up for the position from the position feedback interface selected with
Motor Control Feedback Select
(03.026). To perform a Stationary autotune, set Pr
00.040
to 1, and provide the drive with both an enable signal (terminal 2
and 6) and a run signal (terminal 11 or 13).
•
Rotating Autotune
The rotating autotune must be performed on unloaded motor. This test can be used to measure all the necessary parameters for the basic control and
parameters for cancelling the effects of the cogging torque.
During the rotating autotune,
Rated Current
(00.046) is applied and the motor is rotated by 2 electrical revolutions (i.e. up to 2 mechanical revolutions) in the
required direction. If sensorless mode is not selected then the
Position Feedback Phase Angle
(00.043) is set-up for the position from the position feedback
interface selected with
Motor Control Feedback Select
(03.026). A stationary test is then performed to measure
Stator Resistance
(05.017),
Ld
(05.024),
Maximum Deadtime Compensation
(05.059),
Current At Maximum Deadtime Compensation
(05.060) and
No Load Lq
(05.072).
Stator Resistance
(05.017)
and
Ld
(05.024) are used to set up
Current Controller Kp Gain
(00.038) and
Current Controller Ki Gain
(00.039). This is only done once during the test, and
so the user can make further adjustments to the current controller gains if required. To perform a Rotating autotune, set Pr
00.040
to 2, and provide the drive
with both an enable signal (terminal 2 & 6) and a run signal (terminal 11 or 13).
•
Mechanical load measurement test using signal injection
The mechanical load measurement test using signal injection, measures the mechanical characteristic of the motor and load by rotating the motor at the
speed defined by the present speed reference and injecting a series of speed test signals. This test should only be used provided all the basic control
parameters (including
Torque Per Amp
(05.032)) have been set-up correctly and the speed controller parameters should be set to conservative levels, such
as the default values, so that the motor is stable when it runs. The test measures the motor and load inertia, which can be used in automatic set-up of the
speed controller gains and in producing a torque feed-forward term. If
Mechanical Load Test Level
(05.021) is left at its default value of zero then the peak
level of the injection signal will be 1 % of the maximum speed reference subject to a maximum of 500 rpm. If a different test level is required then
Mechanical
Load Test Level
(05.021) should be set to a non-zero value to define the level as a percentage of the maximum speed reference, again subject to a maximum
of 500 rpm. The user defined speed reference which defines the speed of the motor should be set to a level higher than the test level, but not high enough for
flux weakening to become active. In some cases, however it is possible to perform the test at zero speed provided the motor is free to move, but it may be
necessary to increase the test signal from the default value. The test will give the correct results when there is a static load applied to the motor and in the
presence of mechanical damping. This test should be used if possible, however for sensorless mode, or if the speed controller cannot be set up for stable
operation an alternative test is provided (
Autotune
(00.040) = 4) where a series of torque levels are applied to accelerate and decelerate the motor to measure
the inertia.
1.
A rotating test is performed in which the motor is accelerated with the currently selected ramps up to the currently selected speed reference, and
this speed is maintained for the duration of the test.
Motor And Load Inertia
(03.018) and
Inertia Times 1000
(04.033) are set up.
To perform this autotune test, set Pr
00.040
to 3 and provide the drive with both an enable signal (terminal 2 and 6) and a run signal (terminal 11 or 13).
•
Mechanical load measurement using applied torque
Auto-tune test 3 should normally be used for mechanical load measurement, but under some circumstances this test may be used as an alternative. This test
is likely to give incorrect results if standard ramp mode is active. A series of progressively larger torque levels are applied to the motor (20 %, 40 % ... 100 %
of rated torque) to accelerate the motor up to 3/4 x
Rated Speed
(00.045) to determine the inertia from the acceleration/deceleration time. The test attempts
to reach the required speed within 5s, but if this fails the next torque level is used. When 100 % torque is used the test allows 60 s for the required speed to
be reached, but if this is unsuccessful, a trip is initiated. To reduce the time taken for the test it is possible to define the level of torque to be used for the test
by setting
Mechanical Load Test Level
(05.021) to a non-zero value. When the test level is defined the test is only carried out at the defined test level and 60
s is allowed for the motor to reached the required speed. It should be noted that if the maximum speed allows for flux weakening then it may not be possible
to achieve the required torque level to accelerate the motor fast enough. If this is the case, the maximum speed reference should be reduced.
1
. The motor is accelerated in the required direction up to 3/4 of the maximum speed reference and then decelerated to zero speed.
2
. The test is repeated with progressively higher torques until the required speed is reached.
3.
Motor And Load Inertia
(03.018) and
Inertia Times 1000
(04.033) are set up. To perform this autotune test, set Pr 00.040 to 4 and provide the drive
with both an enable signal (terminal 2 and 6) and a run signal (terminal 11 or 13).
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