Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up Turbo PMAC-Based Commutation and/or Current Loop
99
The amplifier manual should specify the level of current that provides full-range feedback from the
ADCs. Then take the instantaneous current limit for the drive or for the motor, whichever is less, and set
Ixx69 according to the following relationship:
ADCs. Then take the instantaneous current limit for the drive or for the motor, whichever is less, and set
Ixx69 according to the following relationship:
=
377
,
28
*
urrent
FullRangeC
tLimit
InstCurren
,
377
,
28
min
69
Ixx
If the drive outputs analog current readings and the ADCs are on the interface board, the full-range
current value must be calculated from the volts-per-amp gain of the current sensing in the drive and the
full-range voltage into the interface board.
current value must be calculated from the volts-per-amp gain of the current sensing in the drive and the
full-range voltage into the interface board.
If a non-zero value of Ixx77 magnetization current will be used, for induction motor control or for field
weakening of a permanent-magnet brushless motor, then Ixx69 should be replaced in the above equation
by
weakening of a permanent-magnet brushless motor, then Ixx69 should be replaced in the above equation
by
2
77
Ixx
2
69
Ixx
+
.
In early testing, it may be desirable to set Ixx69 to an artificially low value to prevent accidental
overcurrent commands into the motor.
overcurrent commands into the motor.
Continuous Current Limit: Ixx57
Ixx57 specifies the magnitude of the continuous current limit for the motor/drive system for integrated-
current algorithms for thermal protection. If Ixx57 is greater than 0, Turbo PMAC uses I
Ixx57 specifies the magnitude of the continuous current limit for the motor/drive system for integrated-
current algorithms for thermal protection. If Ixx57 is greater than 0, Turbo PMAC uses I
2
T protection,
squaring the value of the current before integrating it. This is appropriate when the most temperature-
sensitive component is resistive in nature (such as the motor windings). If Ixx57 is less than 0, Turbo
PMAC uses |I|T protection, just taking the absolute value of the current before integrating it. This is
appropriate when the most temperature-sensitive component has an essentially fixed voltage across it, as
with a fully-on bipolar transistor.
sensitive component is resistive in nature (such as the motor windings). If Ixx57 is less than 0, Turbo
PMAC uses |I|T protection, just taking the absolute value of the current before integrating it. This is
appropriate when the most temperature-sensitive component has an essentially fixed voltage across it, as
with a fully-on bipolar transistor.
Usually, it is the continuous current rating of the drive that is used for a motor’s Ixx57. Even if its
continuous current rating is somewhat higher than that of the motor, usually its thermal time constant is
so much shorter that the integrated current parameters are set to protect it first. Ixx57 is calculated in a
manner similar to Ixx69:
continuous current rating is somewhat higher than that of the motor, usually its thermal time constant is
so much shorter that the integrated current parameters are set to protect it first. Ixx57 is calculated in a
manner similar to Ixx69:
377
,
28
*
urrent
FullRangeC
tLimit
ContCurren
57
Ixx
=
Integrated Current Limit: Ixx58
Ixx58 sets the permitted limit of the time-integrated current over the continuous current value. If the
time-integrated current exceeds this threshold, Turbo PMAC will kill this axis as it would for an amplifier
fault. Typically, this parameter is set by noting the drive specification for time permitted at the
instantaneous current limit. If I
Ixx58 sets the permitted limit of the time-integrated current over the continuous current value. If the
time-integrated current exceeds this threshold, Turbo PMAC will kill this axis as it would for an amplifier
fault. Typically, this parameter is set by noting the drive specification for time permitted at the
instantaneous current limit. If I
2
T protection is used, this specification is used in the following equation:
(sec)
ime
PermittedT
*
)
Hz
(
eRate
ServoUpdat
*
2
768
,
32
2
57
Ixx
2
77
Ixx
2
69
Ixx
58
Ixx
−
+
=
If |I|T protection is used, this specification is used in the following equation:
(sec)
ime
PermittedT
*
)
Hz
(
eRate
ServoUpdat
*
768
,
32
2
57
Ixx
2
77
Ixx
2
69
Ixx
58
Ixx
−
+
=
Refer to the Making an Application Safe section for a more detailed explanation of I
2
T protection.
Commutation Phase Angle: Ixx72
Ixx72 controls the angular relationship between the phases of a multiphase motor. When Turbo PMAC is
closing the current loop digitally for Motor xx, the proper setting of this variable is dependent on the
polarity of the current measurements.
Ixx72 controls the angular relationship between the phases of a multiphase motor. When Turbo PMAC is
closing the current loop digitally for Motor xx, the proper setting of this variable is dependent on the
polarity of the current measurements.