User guide

8-8
FlexPak 3000 DC Drive Software Reference
8.3.1 Configuring Automatic Field Weakening
The Field Current Regulator kit can provide automatic field weakening. Field
weakening can only be used with speed-regulated drives.
Important:
Automatic field weakening cannot be used if
FEEDBACK SELECT
is set to
ARMATURE VOLT
.
When
ARMATURE VOLTAGE
(P.289) exceeds
FLD WEAKEN THRESHOLD
(P.518), the field
begins to weaken and the field control loop begins regulating armature voltage. When
field auto weakening is enabled, the drive uses the values of
ARMATURE VOLTAGE
(P.289) and
FLD WEAKEN THRESHOLD
(P.518) to try to maintain a zero input to the first
PI
block. If armature voltage increases, a negative value is input to the
PI
block, which
decreases the high limit to the next
PI
block. This reduces field current, subsequently
lowering the armature voltage, bringing the input to the first
PI
block closer to zero.
If
IR
compensation is used, the threshold where the field control loop begins regulating
armature voltage is
FLD WEAKEN THRESHOLD
(P.518) less
IR COMPENSATION
(P.206) at
rated armature current.
To use automatic field weakening, set
FIELD AUTO WEAKEN
(P.517) to
ENABLE
.
To turn off automatic field weakening, set
FIELD AUTO WEAKEN
(P.517) to
DISABLE
. If
automatic field weakening is disabled, the field current
PI
block high limit is fixed at 180
degrees.
If needed, you can use
FLD WEAKEN LEAD FREQ
(P.520) and
FLD WEAKEN PROP GAIN
(P.519) to modify the lead frequency and gain of the field auto weaken
PI
block.
MOTOR HOT FLD AMPS
(P.510)
Motor nameplate
value of the rated hot
field amps. This input
is the basis of field
current scaling.
Parameter Range:
0.11 to installed supply rating (4.00, 10.00, or 20.00
amps)
Default Setting:
0.01 amps
Parameter Type:
Configurable
OIM Menu Path(s):
Field - Field Current Regulator - Field Loop Feedback
Scaling
If the factory defaults are restored, or if a valid value has not yet been entered for
this parameter, the DC field voltage is fixed at 150V on a 230VAC line, or at 300V
on a 460VAC line.
!
ATTENTION:
The incorrect configuration of this parameter can cause a
motor overvoltage condition. Configure
MOTOR HOT FLD AMPS
(P.510) to
the motor nameplate value. Failure to observe this precaution can result
in bodily injury and damage to the equipment.
!
ATTENTION:
The incorrect configuration of the parameters for this loop
can cause a motor overvoltage condition. Configure
MOTOR HOT FLD AMPS
(P.510) to the motor’s nameplate value. Failure to observe this precaution
can result in bodily injury and damage to the equipment.