80
Digitax HD M753 Control User Guide
Issue Number: 3
8.1.2
RFC-S Sensorless mode
Permanent magnet motor without 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 three autotune tests available in RFC-S sensorless mode, a stationary autotune and an inertia measurement test.
•
Stationary Autotune (Pr
00.040
{
05.012
}
= 1)
The stationary autotune can be used to measure all the necessary parameters for basic control. The tests measures
Stator Resistance
(05.017),
Ld
(05.024),
No Load Lq
Pr
00.056
{
05.072
},
Maximum Deadtime Compensation
(05.059) and
Current At Maximum Deadtime Compensation
(05.060). 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
Ld
(05.024) are then used to set up
Current controller Kp Gain
Pr
00.038
{
04.013
} and
Current Controller Ki Gain
Pr
00.039
{
04.014
}. To perform a Stationary
autotune, set Pr
00.040
to 1, and provide the drive with both an enable signal (terminal 2 & 6) and a run signal (terminal 11 or 13).
•
Rotating Autotune (Pr
00.040
{
05.012
}
= 2)
In sensorless mode, if Rotating autotune is selected (Pr
00.040
= 2), then a stationary autotune is performed.
•
Inertia measurement test (Pr
00.040
{
05.012
}
= 4)
NOTE
: It is not possible to perform this test if, after autotune, the ratio
No load Lq
Pr
00.056
{
05.072
} /
Ld
(05.024) < 1.1 and Pr
00.054 {05.064}
has been set
to Non-salient.
The inertia measurement test can measure the total inertia of the load and the motor. This is used to set the speed loop gains (see Speed loop gains) and to
provide torque feed-forwards when required during acceleration. The test may give inaccurate results, if the motor rated speed is not set to the correct value
for the motor, or if standard ramp mode is active. During the inertia measurement test 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
Pr
00.045
{
05.008
} to determine the inertia from the acceleration/
deceleration time. The test attempts to reach the required speed within 5 s, 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 unsucessful an Autotune 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 reach 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 quickly enough. If this is the case, the maximum speed
reference should be reduced. To perform an Inertia measurement autotune, set Pr
00.040
to 4, and provide the drive with both an enable signal (on terminal 2
& 6) and a run signal (on terminal 11 or 13).
Following the completion of an autotune test the drive will go into the inhibit state. The drive must be placed into a controlled disable condition before the drive
can be made to run at the required reference. The drive can be put in to a controlled disable condition by removing the Safe Torque Off signal from terminal 2
& 6, setting the drive Enable Parameter (
06.015
) to Off (0) or disabling the drive via the control word (Pr
06.042
& Pr
06.043
).
Pr 00.038 {04.013} / Pr 00.039 {04.014}
Current Loop Gains
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
00.038
{
04.013
} is the most critical value in controlling the performance. The values for the current loop
gains can be calculated by performing a stationary or rotating autotune (see
Autotune
Pr
00.040
, earlier in this table) the drive measures the
Stator
Resistance
(05.017) and
Transient Inductance
(05.024) of the motor and calculates the current loop gains.
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 the integral
gain may need to have a significantly higher value.
Summary of Contents for Digitax HD M753 EtherCAT
Page 261: ......
Page 262: ...0478 0461 03...