Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
100
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
If the phase current sensors and ADCs in the amplifier are set up so that a positive PWM voltage
command for a phase yields a negative current measurement value, Ixx72 must be set to a value less than
1024: 683 for a 3-phase motor, or 512 for a DC brush motor. If these are set up so that a positive PWM
voltage command yields a positive current measurement value, Ixx72 must be set to a value greater than
1024: 1365 for a 3-phase motor, or 1536 for a DC brush motor. The testing described below will show
how to determine the proper polarity.
command for a phase yields a negative current measurement value, Ixx72 must be set to a value less than
1024: 683 for a 3-phase motor, or 512 for a DC brush motor. If these are set up so that a positive PWM
voltage command yields a positive current measurement value, Ixx72 must be set to a value greater than
1024: 1365 for a 3-phase motor, or 1536 for a DC brush motor. The testing described below will show
how to determine the proper polarity.
The direct-PWM algorithms in the Turbo PMAC are optimized for 3-phase motors and will cause
significant torque ripple when used with 2- or 4-phase motors. Delta Tau has created user-written phase
algorithms for these motors; contact the factory if interested in obtaining these.
significant torque ripple when used with 2- or 4-phase motors. Delta Tau has created user-written phase
algorithms for these motors; contact the factory if interested in obtaining these.
CAUTION
It is very important to set the value of Ixx72 properly for your system; otherwise
the current loop will have unstable positive feedback and want to saturate. This
could cause damage to the motor, the drive, or both, if overcurrent shutdown
features do not work properly. If unsure of the current measurement polarity in
your drive, consult the Testing PWM and Current Feedback Operation section.
the current loop will have unstable positive feedback and want to saturate. This
could cause damage to the motor, the drive, or both, if overcurrent shutdown
features do not work properly. If unsure of the current measurement polarity in
your drive, consult the Testing PWM and Current Feedback Operation section.
For commutation with digital current loops, the proper setting of Ixx72 is unrelated to the polarity of the
encoder counter. This is different from commutation with an analog current loops (sine-wave control), in
which the polarity of Ixx72 (less than or greater than 1024) must match the encoder counter polarity.
With the digital current loop, the polarity of the encoder counter must be set for proper servo operation.
With the analog current loop, once the Ixx72 polarity match has been made for commutation, the servo
loop polarity match is guaranteed.
encoder counter. This is different from commutation with an analog current loops (sine-wave control), in
which the polarity of Ixx72 (less than or greater than 1024) must match the encoder counter polarity.
With the digital current loop, the polarity of the encoder counter must be set for proper servo operation.
With the analog current loop, once the Ixx72 polarity match has been made for commutation, the servo
loop polarity match is guaranteed.
Special Instructions for Direct-PWM Control of Brush Motors
A few special settings must be made to use the direct-PWM algorithms for DC brush motors. The basic
idea is to trick the commutation algorithm into thinking that the commutation angle is always stuck at 0
degrees, so current into the A phase is always quadrature (torque-producing) current. This section
summarizes what must be done in terms of variable setup; some of these settings have been discussed
elsewhere as well.
These instructions assume:
idea is to trick the commutation algorithm into thinking that the commutation angle is always stuck at 0
degrees, so current into the A phase is always quadrature (torque-producing) current. This section
summarizes what must be done in terms of variable setup; some of these settings have been discussed
elsewhere as well.
These instructions assume:
•
The brush motor’s rotor field comes from permanent magnets or a wound field excited by a separate
means; the field is not controlled by one of the phases of this channel.
means; the field is not controlled by one of the phases of this channel.
•
The two leads of the brush motor’s armature are connected to amplifier phases (half-bridges) that are
driven by the A and C-phase PWM commands from Turbo PMAC. The amplifier may have an
unused B-phase half-bridge, but this does not need to be present.
driven by the A and C-phase PWM commands from Turbo PMAC. The amplifier may have an
unused B-phase half-bridge, but this does not need to be present.
Settings that are the same as for permanent-magnet brushless servo motors with an absolute phase reference:
•
Ixx01 = 1 (commutation directly on Turbo PMAC) or Ixx01=3 (commutation over the MACRO ring).
•
Ixx02 should contain the address of the PWM A register for the output channel used or the MACRO
Node register 0 (these are the defaults), just as for brushless motors.
Node register 0 (these are the defaults), just as for brushless motors.
•
Ixx29 and Ixx79 phase offset parameters should be set to minimize measurement offsets from the A
and B-phase current feedback circuits, respectively.
and B-phase current feedback circuits, respectively.
•
Ixx61, Ixx62, and Ixx76 current loop gains are set just as for brushless motors.
•
Ixx73 = 0, Ixx74 = 0: These default settings ensure that Turbo PMAC will not try to do a phasing
search move for the motor. A failed search could keep Turbo PMAC from enabling this motor.
search move for the motor. A failed search could keep Turbo PMAC from enabling this motor.
•
Ixx77 = 0 to command zero direct (field) current.
•
Ixx78 = 0 for zero slip in the commutation calculations.