Parameter
structure
Keypad and
display
Parameter
x.00
Parameter
description format
Advanced parameter
descriptions
Macros
Serial comms
protocol
Electronic
nameplate
Performance RFC mode
Menu 3
Closed-loop
Unidrive SP Advanced User Guide
65
Issue Number: 10 www.controltechniques.com
When closed-loop vector mode without position feedback is used a filter with a 4ms time constant is automatically included in the speed feedback as
this is required for this system to operate correctly. This will reduce the possible bandwidth of the speed controller compared with the bandwidth
possible when position feedback is used. Particularly when operating above rated speed it may be necessary to include further filtering (Pr
4.12
set to
a value between 1.0 and 5.0ms) to achieve stable operation.
The phase angle between the rotor flux in a servo motor and the encoder position is required for the motor to operated correctly. If the phase angle is
known it can be set in this parameter by the user. Alternatively the drive can automatically measure the phase angle by performing a phasing test (see
Pr
on page 117). When the test is complete the new value is written to this parameter. The encoder phase angle can be modified at any time and
becomes effective immediately. This parameter has a factory default value of 0.0, but is not affected when defaults are loaded by the user.
The alignment required for zero encoder phase angle (i.e. Pr
3.25
= 0.0) is given below for different feedback devices. Forward rotation of the motor
is produced when Vu leads Vv leads Vw. Although it is not essential, forward rotation of a motor is normally defined as clockwise when looking at the
motor shaft end. When the motor is rotating forwards the motor speed is shown as positive and the position increases.
Encoder with commutation signals (Ab.Servo, Fd.Servo, Fr.Servo)
The alignment required between the no-load motor voltages and the commutation signals for Pr
3.25
= 0 is shown in the following diagram below:
It should be noted that if the encoder is advanced (i.e. the UVW signals are moved to the right with respect to the voltages) the phasing angle in
Pr
3.25
is increased from zero. If the encoder is retarded the phasing angle changes to 359.9
°
and then reduces towards zero.
The encoder can be aligned statically by connecting the motor to a DC power supply as shown:
3.25
Encoder phase angle
Drive modes
Servo
Coding
Bit
SP
FI
DE Txt VM DP ND RA NC NV
PT
US RW BU PS
1
1
1
1
1
Range
Servo
0.0 to 359.9 ° electrical
Second motor
parameter
Servo
Pr
21.20
Update rate
Background read
Vwu
Vvw
Vuv
Vw
Vv
Vu
No load phase
voltages
No load line
voltages
U Encoder commutation
signals (high = U > U)
V
W
Encoder alignment for zero encoder phase angle
Encoder angle
180
o
120
o
60
o
o
0
o
300
o
240
o
180
32768 43691 54613 0 10923 21845 32768
+
_
U
V
W
Summary of Contents for unidrive sp
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