Curtis 1243
GEN
2 Manual
39
3 — PROGRAMMABLE PARAMETERS:
Field Parameters
FIELD MAP
The
fi
eld map de
fi
nes the relationship between armature current and
fi
eld
current under steady-state drive conditions. The shape of the
fi
eld 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
fi
eld map parameter adjusts the
fi
eld 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
fi
eld 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
F
IE
LD
C
U
R
R
E
N
T
Field Map Start
Field Map Midpoint
100%
Drive C/L
0
0
Field Min
Field Max
Field Map
(50%)
ARMATURE CURRENT
F
IE
LD
C
U
R
R
E
N
T
Field Map Start
Field Map Midpoint
100%
Drive C/L
0
0
Field Min
Field Max
Field Map
(20%)
Decreasing the
fi
eld map parameter reduces the
fi
eld current at a given
armature current. As the
fi
eld 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
fi
eld map parameter is tuned as part of the vehicle performance
adjustment process (Section 5).