Wesley BCT-6200-6SA - Manual (Page 47)

Curtis 1243
GEN
2 Manual, Rev. B 39
3 — PROGRAMMABLE PARAMETERS: Field Parameters
FIELD MAP
The field map defines the relationship between armature current and field current
under steady-state drive conditions. The shape of the field map is determined
by the programmed Field Min, Field Max, Field Map, Field Map Start, and
M1-M4 Drive C/L settings.
As shown in Figure 20, the field map parameter adjusts the field current
at the Field Map Midpoint, which is located halfway between the programmed
Field Map Start and the programmed M1-M4 Drive C/L. With the field map
parameter set at 50%, the motor’s field current increases linearly with increasing
armature current—thus emulating a series wound motor.
Fig. 20 Field current
relative to armature
current, with field map
parameter set at 50%
and 20%.
ARMATURE CURRENT
FIELD CURRENT
Field Map Start Field Map Midpoint 100%
Drive C/L
0
0
Field Min
Field Max
Field Map
(50%)
ARMATURE CURRENT
FIELD CURRENT
Field Map Start Field Map Midpoint 100%
Drive C/L
0
0
Field Min
Field Max
Field Map
(20%)
Decreasing the field map parameter reduces the field current at a given
armature current. As the field current is reduced, the motor will be able to
maintain speeds closer to the maximum speed value as its load increases;
however, the motor’s capability to produce torque at these higher speeds will
decrease. With the Field Map reduced to 20%, the field current at the Field
Map Midpoint will exceed Field Min by 20% of the range between Field Min
and Field Max.
The field map parameter is tuned as part of the vehicle performance
adjustment process (Section 5).