Delta Tau GEO BRICK LV Manuel D’Utilisation
Turbo PMAC User Manual
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
129
The higher the value of Ixx77 (before saturation), the more torque is produced per unit of quadrature current
commanded from the servo loop, but the higher the back-EMF generator voltage produced per unit of motor
velocity, so the lower the maximum velocity can be achieved from a given supply voltage. The lower the
value of Ixx77, the less torque is produced per unit of commanded quadrature current, but the lower the
back-EMF voltage produced per unit of velocity, so the higher the velocity that can be achieved.
In most applications, a single value of Ixx77 will be set and left constant for the application. However, it
is possible to change Ixx77 dynamically as a function of speed, lowering it at high speeds so as to keep
the back-EMF under the supply voltage, extending the motor’s speed range. Generally, this technique is
known as field weakening” and can be implemented in a PLC program.
If the Turbo Setup program is not used to set the value of the Ixx77 magnetization-current parameter, it is
best to do so experimentally. With a good value of Ixx78 set, simply issue a low-valued O-command
(e.g. O10) at each of several settings of Ixx77 and observe the end velocity the unloaded motor achieves.
This can be done by watching the real-time velocity read-out in the Executive program’s position
window. If using the data gathering feature, also note the rate of acceleration to that speed.
This velocity is known as the base speed for the motor for that setting. Typically, a value of 3200 to 3500
for Ixx77 will achieve the approximately a base speed equivalent to the rated speed of the motor when run
directly from a 50 Hz or 60 Hz line.
If the test values of Ixx77 are low enough that none of them magnetically saturate the rotor, the base
speeds in the test will be approximately inversely proportional to the value of Ixx77 (and the accelerations
to that speed will be approximately proportional to Ixx77). If you start increasing Ixx77 into the range
that causes magnetic saturation of the rotor, increases in Ixx77 will not cause further lowering of base
speed and further increase in rate of acceleration to that speed.
Many users will want a value of Ixx77 as high as possible without causing rotor saturation. These users
will want to find values of Ixx77 that do cause saturation, then reduce Ixx77 just enough to bring it out of
saturation. The Turbo Setup program finds this setting automatically.
commanded from the servo loop, but the higher the back-EMF generator voltage produced per unit of motor
velocity, so the lower the maximum velocity can be achieved from a given supply voltage. The lower the
value of Ixx77, the less torque is produced per unit of commanded quadrature current, but the lower the
back-EMF voltage produced per unit of velocity, so the higher the velocity that can be achieved.
In most applications, a single value of Ixx77 will be set and left constant for the application. However, it
is possible to change Ixx77 dynamically as a function of speed, lowering it at high speeds so as to keep
the back-EMF under the supply voltage, extending the motor’s speed range. Generally, this technique is
known as field weakening” and can be implemented in a PLC program.
If the Turbo Setup program is not used to set the value of the Ixx77 magnetization-current parameter, it is
best to do so experimentally. With a good value of Ixx78 set, simply issue a low-valued O-command
(e.g. O10) at each of several settings of Ixx77 and observe the end velocity the unloaded motor achieves.
This can be done by watching the real-time velocity read-out in the Executive program’s position
window. If using the data gathering feature, also note the rate of acceleration to that speed.
This velocity is known as the base speed for the motor for that setting. Typically, a value of 3200 to 3500
for Ixx77 will achieve the approximately a base speed equivalent to the rated speed of the motor when run
directly from a 50 Hz or 60 Hz line.
If the test values of Ixx77 are low enough that none of them magnetically saturate the rotor, the base
speeds in the test will be approximately inversely proportional to the value of Ixx77 (and the accelerations
to that speed will be approximately proportional to Ixx77). If you start increasing Ixx77 into the range
that causes magnetic saturation of the rotor, increases in Ixx77 will not cause further lowering of base
speed and further increase in rate of acceleration to that speed.
Many users will want a value of Ixx77 as high as possible without causing rotor saturation. These users
will want to find values of Ixx77 that do cause saturation, then reduce Ixx77 just enough to bring it out of
saturation. The Turbo Setup program finds this setting automatically.
Direct Microstepping of Motors (Open-Loop Commutation)
Turbo PMAC has the ability to do open-loop microstepping (direct microstepping) of standard stepper
motors, working off internally generated pseudo-feedback for both commutation and servo algorithms.
This technique is different from using Turbo PMAC with a pulse-and-direction output to command an
external microstepping drive; that technique does not utilize Turbo PMAC’s commutation algorithms at all.
When microstepping, Turbo PMAC provides two analog outputs that are used as current commands for
phases of the motor. Typically for a microstepping motor, the two phases are electrically independent and
90o out of phase with each other. In this case, the two outputs are simply bi-directional current
commands for the H-bridge amplifiers driving each phase. These amplifiers can be simple torque-mode
(current-mode) DC brush motor amplifiers.
Turbo PMAC’s microstepping algorithm provides 2048 microsteps per electrical cycle, which is 512
microsteps/step. On a typical 200-step/revolution motor, this amounts to 102,400 microsteps per
revolution. With the default phase update frequency of 9 kHz, Turbo PMAC can slew at over 4,600,000
microsteps/second (9000 full steps per second). With a small number of motors and/or fast versions of
the Turbo PMAC, higher phase-update frequencies can be used.
motors, working off internally generated pseudo-feedback for both commutation and servo algorithms.
This technique is different from using Turbo PMAC with a pulse-and-direction output to command an
external microstepping drive; that technique does not utilize Turbo PMAC’s commutation algorithms at all.
When microstepping, Turbo PMAC provides two analog outputs that are used as current commands for
phases of the motor. Typically for a microstepping motor, the two phases are electrically independent and
90o out of phase with each other. In this case, the two outputs are simply bi-directional current
commands for the H-bridge amplifiers driving each phase. These amplifiers can be simple torque-mode
(current-mode) DC brush motor amplifiers.
Turbo PMAC’s microstepping algorithm provides 2048 microsteps per electrical cycle, which is 512
microsteps/step. On a typical 200-step/revolution motor, this amounts to 102,400 microsteps per
revolution. With the default phase update frequency of 9 kHz, Turbo PMAC can slew at over 4,600,000
microsteps/second (9000 full steps per second). With a small number of motors and/or fast versions of
the Turbo PMAC, higher phase-update frequencies can be used.