Rockwell Automation FlexPak 3000 Drive Field Current Regulator Kit, 911FK0041, 911FK0101, 911FK015 - Manual (Page 41)

Field Current Regulator Description A-5
Field Loss
When the Field Current Regulator is operating in fixed voltage mode, a field current
loss fault will be generated only when there is a complete loss of field current. When
the Field Current Regulator is regulating field current (that is, not in fixed voltage
mode), a field current loss fault will be generated when the field current drops below
the user-set
FIELD LOSS THRESHOLD .
The same field feedback signal used by the Field Current Regulator is used by the
field loss detection circuit. The field current feedback will be compared against a
user-entered
FIELD LOSS THRESHOLD . If the feedback is less than the threshold value, a
fault will be generated. FIELD LOSS THRESHOLD is entered as a percentage of
MOTOR HOT FLD AMPS (0-100% (speed regulator), 50-100% (armature voltage
regulator)). FIELD ECONOMY REF must be set above FIELD LOSS THRESHOLD to avoid field
loss faults when the drive enters field economy.
A field loss fault will also occur if the digital value on the A/D converter reaches full
scale (approximately 28% above the rated field output).
The Regulator board hardware jumper, J20 FIELD LOSS DETECT , is designed to allow
the user to separately excite the motor field winding, and is not intended as a means
of bypassing field loss detection when using an internal field supply. Therefore, when
the Field Current Regulator kit is installed, this jumper is ignored. Note that leaving
J20 in the DISABLE position will NOT disable field loss detection.
Field Economy
The output parameter FIELD ECONOMY ACTIVE indicates when field economy is active.
Field economy becomes active after a user-defined time delay ( FIELD ECONOMY DELAY )
from the time the motor stops or the drive is powered up. When the Field Current
Regulator is operating in fixed voltage mode, a constant field voltage is generated,
regardless of the state of
FIELD ECONOMY ACTIVE .
The Field Current Regulator will provide field economy with a user-adjustable field
current reference (
FIELD ECONOMY REF ). This parameter is entered as a percentage of
MOTOR HOT FLD AMPS . FIELD ECONOMY REF must be set above FIELD LOSS THRESHOLD to
avoid nuisance field loss faults.
Overspeed Protection
Overspeed detection is active only when a tachometer is being used ( FEEDBACK
SELECT
≠
ARMATURE VOLT ). Because of this, the amount of field weakening is limited
when the drive is configured as a voltage regulator ( FEEDBACK SELECT = ARMATURE
VOLT ).
Overvoltage Protection
Armature overvoltage protection is always active, regardless of the type of feedback.
This will reduce the chance of overvoltaging the armature due to a weakened field. An
overvoltage fault will occur when the armature terminal voltage exceeds 130 percent
of
MOTOR RATED ARM VOLTS .