Wesley BC-6200-8SA - Manual (Page 49)

Curtis 1268 Manual, Rev. D
43
8
Transitioning from Flat Ground to Downhill
To ensure smoothness on transitions from positive drive current to negative
regen current, set the
NEG FLD MAP ST (negative field map start) greater than zero
to provide a constant value of field current as the motor transitions between
drive and regen braking.
If speed “hunting” or oscillation occurs on downhill grades, reduce the NEG
FIELD MAX and NEG FLD RAMP parameters or increase the NEG FLD MAP EN parameter
to ensure an initally shallower negative field map profile.
Note: The “negative field map” refers to the field and armature (regen
braking) current relationship regardless of forward or reverse direction.
9
Hill Climbing
The vehicle response to increased gradients such as hills and loading ramps
can be tuned via the
FIELD RAMP parameter. Decreasing the FIELD RAMP value
allows faster vehicle speeds while climbing, but it will also have the effect of
reducing the ability of the controller to generate torque in the vehicle’s mid
range speeds.
step 1. If faster vehicle speed is desired when climbing ramps, decrease
FIELD RAMP until the desired ramp climbing speed is attained. It
should be noted that if the motor’s torque capability is exceeded
under the conditions of load and ramp gradient, vehicle speed
will be limited by the motor’s capability and the desired vehicle
speed may not be attainable. The system will find a compromise
point at which sufficient motor torque is generated to climb the
ramp at an acceptable speed. If
FIELD RAMP is reduced to 0% and
the desired speed is still not attained, the system is being limited
by the motor’s torque capability under these conditions.
Caution should be used in reducing FIELD RAMP since at low
FIELD RAMP values it is possible that the motor could be operated
outside its safe commutation region.
step 2. If the drive system cannot produce sufficient torque for a fully
loaded vehicle to climb the desired ramp, try increasing the FIELD
RAMP , FIELD MAX , and/or MAIN C/L . The impact of increasing these
values on other driving characteristics must be evaluated. Increas-
ing the
FIELD MAX will provide more field current, and increasing
the MAIN C/L will provide more armature current. If FIELD MAX is
set at the manufacturer’s specified limit and the MAIN C/L is set at
the rated maximum, then vehicle speed up the ramp is limited
by the motor or the vehicle’s gearing and cannot be increased
by tuning the controller.
Note: To determine whether the controller’s armature current
is at its set value during ramp climbing, read the Arm Current
in the programmer’s Monitor menu.
5 — TUNING GUIDE