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the motor
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operation
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UL Listing
Information
224
Affinity User Guide
www.controltechniques.com Issue Number: 5
If
σ
L
s
cannot be measured it can be calculated from the steady state
per-phase equivalent circuit of the motor as follows:
I
fs
is the peak full scale current feedback = K
C
x
√
2 / 0.45. Where K
C
is defined in Table 11-5.
V
fs
is the maximum DC bus voltage.
Therefore:
Pr
4.13
= Kp = (L / 167
μ
s) x (K
C
x
√
2 / 0.45 / V
fs
) x (256 / 5)
= K x L x K
C
Where:
K = [
√
2 / (0.45 x V
fs
x 167
μ
s)] x (256 / 5)
This set-up will give a step response with minimum overshoot after a
step change of current reference. The approximate performance of the
current controllers will be as given below. The proportional gain can be
increased by a factor of 1.5 giving a similar increase in bandwidth,
however, this gives at step response with approximately 12.5%
overshoot.
The integral gain (Pr
4.14
) is less critical and should be set so that
Pr
4.14
= Ki = Kp x 256 x T /
τ
m
Where:
τ
m
is the motor time constant (L / R).
R is the per phase stator resistance of the motor (i.e. half the
resistance measured between two phases).
Therefore
Pr
4.14
= Ki = (K x L x K
C
) x 256 x 167
μ
s x R / L
= 0.0427 x K x R x K
C
The above equation gives a conservative value of integral gain. 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
applications) the integral gain may need to have a significantly higher
value.
11.21.11 Catch a spinning motor
Open-loop
When the drive is enabled with this parameter at zero, the output
frequency starts at zero and ramps to the required reference. When the
drive is enabled with this parameter at a non-zero value, the drive
performs a start-up test to determine the motor speed and then sets the
initial output frequency to the synchronous frequency of the motor.
The test is not carried out and the motor frequency starts at zero if one of
the following is true.
•
The run command is given when the drive is in the stop state
•
The drive is first enabled after power-up with Ur_I voltage mode
(Pr
5.14
= Ur_I).
•
The run command is given with Ur_S voltage mode (Pr
5.14
=
Ur_S).
With default parameters the length of the test is approximately 250ms,
however, if the motor has a long rotor time constant (usually large
motors) it may be necessary to extend the test time. The drive will do this
automatically if the motor parameters including the rated load rpm are
set up correctly for the motor.
For the test to operate correctly it is important that the stator resistance
(Pr
5.17
or Pr
21.12
) is set up correctly. This applies even if fixed boost
(Pr
5.14
= Fd) or square law (Pr
5.14
= SrE) voltage mode is being used.
The test uses the rated magnetizing current of the motor during the test,
therefore the rated current (Pr
5.07
, Pr
21.07
and Pr
5.10
, Pr
21.10
) and
power factor should be set to values close to those of the motor,
although these parameters are not as critical as the stator resistance.
For larger motors it may be necessary to increase Pr
5.40
Spin start
boost
from its default value of 1.0 for the drive to successfully detect the
motor speed.
It should be noted that a stationary lightly loaded motor with low inertia
might move slightly during the test. The direction of the movement is
undefined. Restrictions may be placed on the direction of this movement
and on the frequencies detected by the drive as follows:
RFC
When the drive is enabled with this bit at zero, the post ramp reference
(Pr
2.01
) starts at zero and ramps to the required reference. When the
drive is enabled with this bit at one, the post ramp reference is set to the
motor speed.
If catch a spinning motor is not required, this parameter should be set to
zero as this avoids unwanted movement of the motor shaft when zero
speed is required. With larger motors it may be necessary to increase
Pr
5.40
Spin start boost
from its default value of 1.0 for the drive to
successfully detect the motor speed.
11.21.12 Fast Disable
This bit is a duplicate of Pr
8.09
and reflects the state of the enable input.
If the destination of one of the drive digital I/O (Pr
8.21
to Pr
8.26
) is set
to Pr
6.29
and the I/O is set as an input, the state of the input does not
affect the value of this parameter as it is protected, however, it does
provide a fast disable function.
The Enable input to the drive (T31) disables the drive in hardware by
removing the gate drive signals from the inverter IGBT's and also
disables the drive via the software system. When the drive is disabled by
de-activating the Enable input (T31) there can be a delay of up to 20ms
(typically 8ms) before the drive is disabled. However, if a digital I/O is set
up to provide the fast disable function it is possible to disable the drive
within 600
μ
s of de-activating the input. To do this an enable signal
should be given to both the Enable input (T31) and to the digital I/O
selected for the fast disable function. The state of the digital I/O including
the effect of its associated invert parameter is ANDed with the Enable
(T31) to enable the drive.
Drive voltage rating
Vfs
K
200V
415V
2322
400V
830V
1161
575V
990V
973
690V
1190V
809
Switching
frequency
kHz
Current control
sample time
μ
s
Gain
bandwidth
Hz
Phase
delay
μ
s
3
167
TBA
1160
4
125
TBA
875
6
83
TBA
581
8
125
TBA
625
12
83
TBA
415
16
125
TBA
625
6.09
Catch a spinning motor
RW
Uni
US
OL
Ú
0 to 3
Ö
0
RFC
0 to 1
1
Pr 6.09
Function
0
Disabled
1
Detect all frequencies
2
Detect positive frequencies only
3
Detect negative frequencies only
6.29
Hardware enable
RO
Bit
NC
PT
Ú
OFF (0) or On (1)
Ö
Содержание Affinity
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