Curtis 1243GEN2 Manual
59
5 — VEHICLE PERFORMANCE ADJUSTMENT
low battery voltage and with a hot motor. To determine this
value, divide the low battery voltage (typically 70% of nominal)
by the high temperature field winding resistance specification
provided by the manufacturer. Set the Field Max parameter to
this value. This will provide good consistency between motor
performance in both hot and cold states.
STEP 5. For the maximum torque regardless of temperature, set the Field
Max parameter to the motor’s rated absolute maximum field
current. To determine the absolute maximum field current,
divide the nominal battery voltage by the low temperature field
winding resistance specification provided by the manufacturer.
Set the Field Max parameter to this value. This will provide the
maximum possible torque under all conditions.
This has now set the Max Field parameter. The next step is to set the Min Field
parameter. NOTE: The Field Min parameter 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 commu-
tation region and will cause arcing between the brushes and commutator,
significantly reducing motor and brush life. The Field Min parameter value can
be increased from the manufacturer’s specified value to limit the vehicle’s top
speed. (Setting the vehicle top speed will be addressed in tuning procedure
3
.)
If the controller is tuned such that the system is operating outside the
motor’s safe commutation region, there will be audible and visual indications.
Under normal operation, the motor will emit a whine with a pitch that
increases with increasing rotation speed. If a “scratchy” sound is also heard, this
is usually an indication that pin arcing is occurring in the motor and it is
operating outside its safe commutation region. This operation is normally
accompanied by a strong smell from the motor. If the brushes and commutator
bars are visible, arcing may be visible. The further outside the safe commutation
region the motor is operating, the worse the arcing will be. Operation outside
the safe commutation region is very detrimental to the motor. The Field
Min and possibly also the Field Map parameter should be increased until the
indications of arcing stop. Decreasing the Field Map Start parameter will also
help to move operation back into the safe commutation region.
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