Wesley BC-6200-8SA - Manual (Page 42)

36 Curtis 1268 Manual, Rev. D
the winding is reduced. Reductions in the field current over the motor’s typical
operating temperature range can be 10% to 50%. Since the maximum avail-
able field current determines the maximum torque that can be produced by
the motor, the vehicle’s performance under load and up inclines will change
as the motor heats up. The change in performance can be limited by tuning
the motor when it is hot rather than cold. We therefore recommend that this
procedure be performed with a hot motor.
step 1. Using the programmer’s Program Menu, set the drive current
limit ( MAIN C/L ) for both modes to the smaller of: (a) the motor’s
peak armature current rating, or (b) the maximum controller
drive current limit. This value can later be adjusted to establish
the desired vehicle driving feel in each mode.
step 2. Set the REGEN C/L value in each mode to the smaller of: (a) the
maximum motor armature current rating, or (b) the maximum
controller braking current limit. This value can later be adjusted
to establish the desired vehicle braking feel (see Fine Tuning).
step 3. To set FIELD MAX , first decide whether you want to maintain con-
sistent vehicle operation throughout the motor’s temperature
range. If you do, proceed to Step 4. If, however, maintaining
operational consistency across motor temperature is not a concern
and achieving maximum torque is, skip to Step 5.
step 4. For the most consistent operation across temperature, set the
FIELD MAX to the maximum field current available at low battery
voltage with a hot motor. To determine this current, divide the
low battery voltage (typically 70% of nominal) by the high
temperature field winding resistance specification provided by
the manufacturer. Set
FIELD MAX to this value. This will provide
good consistency between motor performance in both hot and
cold states. Skip to Step 6.
step 5. For the maximum torque regardless of temperature, set FIELD MAX
to the motor’s rated absolute maximum field current. To deter-
mine the absolute maximum field current, divide the
nominal
battery voltage by the low temperature field winding resistance
specification provided by the manufacturer. Set
FIELD MAX to this
value. This will provide the maximum possible torque under all
conditions.
This has now set the FIELD MAX parameter.
The next step is to set the FIELD MIN parameter. FIELD MIN should never be set
below the rated value specified by the manufacturer. Operating the motor
at lower field currents than specified will result in operation outside the motor’s
safe commutation region and will cause arcing between the brushes and com-
mutator, significantly reducing motor and brush life.
5 — TUNING GUIDE