Chapter 3 – Configuration
29
Torque Mode Tuning Procedure
Primary Tuning Procedure
1.
Disable the drive.
2.
Configure the drive for
torque tuning mode (DMODE15). In this mode, the drive
commands a bipolar step change in current, proportional to the motor’s continuous
current rating, at a 10 Hz repetition rate. (The drive will ignore torque commands on
its command input terminals which may come from an external device, such as a
servo controller.)
3.
Configure ANALOG MONITOR A to show
commanded d-axis current
(DMONAV16).
4.
Configure ANALOG MONITOR B to show
actual d-axis current (DMONBV17).
5.
Connect one channel of your oscilloscope to the drive’s ANALOG MONITOR A (pin
21). Connect your oscilloscope’s ground to the drive’s ANALOG GROUND (pin 25).
6.
Connect a second channel of your oscilloscope to the drive’s ANALOG
MONITOR B (pin 22). Connect your oscilloscope’s ground to the drive’s ANALOG
GROUND (pin 25).
Adjust your oscilloscope to display commanded versus actual d-axis current. (The
analog monitors can be scaled, in percent, with the DMONAS and DMONBS
commands.)
7.
Enable the drive and observe your system’s response, using the oscilloscope. (The
motor may move back and forth slightly.)
Ringing or an oscillating response indicates that the current loop bandwidth is too
high. To eliminate oscillations:
• decrease bandwidth using the DIBW command.
A sluggish response, or actual current that remains below commanded current,
indicates that bandwidth is too low. To improve the response:
• increase bandwidth by using the DIBW command. However, increasing
bandwidth higher than the default value is usually not helpful.
8.
After you achieve a satisfactory system response, reconfigure the drive for torque
mode (DMODE2). This completes the primary tuning procedure.
If you are unable to achieve a satisfactory response, proceed to the advanced
tuning procedure below.
Advanced Tuning Procedure
1.
Configure the drive for torque tuning mode (DMODE15), and connect an oscillo-
scope, as described in Steps 1 – 6 in the
Primary Tuning Procedure above.
2.
Enable the drive and observe your system’s response.
Ringing or an oscillating response indicates that the current loop bandwidth is too
high, or the current loop damping is too low. To eliminate oscillations:
• decrease bandwidth using the DIBW command; then, if necessary:
• adjust damping by using the SGIRAT command. Use the value that gives
the best performance.
A sluggish response indicates that bandwidth is too low, or damping is too high. To
improve the response:
• increase bandwidth by using the DIBW command; then, if necessary:
• adjust damping by using the SGIRAT command. Use the value that gives
the best performance.
3.
OPTIONAL: Null the Input Offset.
First: command zero volts by using either of two methods:
Method 1: connect your controller or command voltage source, and
command zero volts; or:
Method 2: disconnect the controller or command voltage source, and short
CMD+ to CMD- (pin 23 to pin 24).
Second: Issue a DCMDZ command to null any offset at the command input.
4.
After you achieve a satisfactory system response, reconfigure the drive for torque
mode (DMODE2). This completes the advanced tuning procedure.
If ringing or oscillations persist, and do not seem to be affected by bandwidth
adjustments, you may need to use notch filters or lead/lag filters. See the Filter
Adjustments procedure at the end of this Tuning section.
www.comoso.com
