Control Techniques Digitax ST Advanced User's Manual page 70

Parameter
Menu 4
structure
4.01 Current magnitude
Bit SP
Coding
Range 0 to DRIVE_CURRENT_MAX A
Update rate 4ms write
This parameter is the r.m.s. current from each output phase of the drive. In normal operation with a permanent magnet servo motor, this parameter
shows the magnitude of the active current in Pr 4.02. When in the field weakening range, the phase currents consist of an active component and a
reactive component. The three phase currents can be combined to form a resultant current vector as shown below:
y
Resultant
output current
Pr 4.02
Pr 4.01
Pr 4.17
x
The resultant current magnitude is displayed by this parameter. The active current is the torque producing current for a motor drive. The reactive
current is the magnetizing or flux producing current.
4.02 Active current
Bit SP
Coding
Range ±DRIVE_CURRENT_MAX A
Update rate 4ms write
The active current is the torque producing current.
Direction of active current
+
-
+
-
The active current is aligned with the y axis of the reference frame. The x axis of the reference frame is aligned with the rotor flux vector. The motor
torque is proportional to the torque producing current when field weakening is not active. Once field weakening is active the torque producing current
is boosted to compensate for the reduction in motor flux.
4.03 Torque demand
Bit SP FI
Coding
Range ±TORQUE_PROD_CURRENT_MAX %
Update rate 4ms write
The torque demand can be derived from the speed controller and/or the torque reference and offset. The units of the torque demand are % of rated
torque. 100% rated torque is defined as the torque produced by 100% rated active current.
4.04 Current demand
Bit SP
Coding
Range ±TORQUE_PROD_CURRENT_MAX %
Update rate 4ms write
The current demand is derived from the torque demand. Provided the motor is not field weakened the torque and current demands are the same. In
the field weakening range the current demand is increased with reduced flux. The level of flux is derived from the motor model within the drive
controllers.
Pr 4.04 = Pr 4.03 x flux / rated flux
70
Keypad and
Parameter x.00
display
FI DE Txt VM DP ND
1 1 2 1
FI DE Txt VM DP ND
1 1 2 1
Direction of rotation
+ Forward (accelerating)
+ Reverse (decelerating)
- Forward (decelerating)
- Reverse (accelerating)
DE Txt VM DP ND
1 1 1 1
FI DE Txt VM DP ND
1 1 1 1
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Parameter Advanced parameter
description format descriptions
RA NC NV PT US RW BU
1 1
RA NC NV PT US RW BU
1 1
Torque direction
RA NC NV PT US RW BU
1 1
RA NC NV PT US RW BU
1 1
Serial comms Electronic
protocol nameplate
PS
1
PS
PS
PS
Digitax ST Advanced User Guide
Issue Number: 1
Performance