Wesley BC-6200-8SA - Manual (Page 31)

25 Curtis 1268 Manual, Rev. D
FIELD MAP END / NEG FLD MAP EN
The field map end parameter defines the armature current at which the field
map clamps to the
FIELD MAX value (see current limit parameters).
Care should be taken to ensure that high FIELD MAP END values do not move
the motor’s operating characteristics outside its safe commutation region.
FIELD RAMP / NEG FLD RAMP
The field ramp parameter defines the shape of the field map curve. It is set as
a percentage of the field current between the
FIELD MIN and FIELD MAX values.
As shown in Figure 9, the FIELD RAMP parameter sets the field current at
the armature current that is halfway between the FIELD MAP START current and the
FIELD MAP END current. This halfway point is called the Field Map Midpoint.
3 — PROGRAMMABLE PARAMETERS: Field Mapping Parameters
Fig. 9 Field map structure.
With FIELD RAMP set at 50% and FIELD MAP START set at zero, the motor’s field
current increases linearly with increasing armature current—thus emulating a
series wound motor. Decreasing the
FIELD RAMP setting reduces the field current
at a given armature current, i.e., it weakens the field. As the field current is
reduced, the motor will be able to achieve higher speeds.
Care should be taken to ensure that excessively low FIELD RAMP values do not
move the motor’s operating characteristics outside its safe commutation region.
FIELD DIR SWAP
The field direction swap parameter changes the polarity of the motor field
output with respect to the direction inputs. If the motor field wiring is reversed
at the motor or controller field terminals, the motor rotation may cause the
vehicle to move in the opposite direction from the direction command. The
FIELD DIR SWAP parameter provides a way to swap the field direction without
physically changing the wiring.
FIELD DIR SWAP = off (default setting, for wiring shown in Figure 3)
Field current flows from F2 » F1 in the Forward direction.
FIELD DIR SWAP = on
Field current flows from F1 » F2 in the Forward direction.