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Curtis 1244 Manual, Rev. E
4. For the most consistent operation across temperature, set the
Field Max parameter 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 the Field Max parameter to this value.
is will provide good consistency between motor performance
in both hot and cold states.
5. For the maximum torque regardless of temperature, set the
Field Max parameter to the motor’s rated absolute maximum
eld 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. is will provide the
maximum possible torque under all conditions.
is has now set the Max Field parameter. e next step is to set the Min Field
parameter. : e 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 com-
mutation region and will cause arcing between the brushes and commutator
significantly reducing motor and brush life. e 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 later in this section.)
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 out-
side its safe commutation region. is operation is normally accompanied by
a strong smell from the motor. If the brushes and commutator bars are visible,
arcing may be visible. e 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. e 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.
6 — VEHICLE PERFORMANCE ADJUSTMENT
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