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Curtis PMC 1204/1205 Manual
HARDWARE INSTALLATION
Main Contactor
Most applications use a main contactor in series with the battery positive
(B+) cable to disconnect all power when the system is turned off, as shown
in Figure 5. A heavy-duty single-pole, single-throw (SPST) contactor with
silver-alloy contacts is recommended, such as an Albright SW80 or
SW180 (available from Curtis).
A coil suppression diode, such as a Curtis PMC p/n MP-1 (which is
rated at 100 volts, 3 amps), should be used on the contactor coil.
The rapid charging of the controller’s internal filter capacitors causes
a high inrush current to flow briefly when the contactor closes. To extend
contact life, a precharge resistor, such as Curtis PMC’s p/n MP-2, is
recommended; the resistor precharges the capacitors and reduces the
inrush current through the contacts. If an inexpensive “can” type sole-
noid is used, the resistor is mandatory to prevent contact welding.
Forward/Reverse Contactors
The forward/reverse contactor coils must match the vehicle’s battery
voltage. Use of two single-pole, double-throw (2×SPDT) contactors is
recommended. Although inexpensive “can” type solenoids can be used,
their ratings are typically not sufficient for long life. Changeover contactor
sets — such as the Albright DC88 and DC182 (available from Curtis) —
are therefore recommended.
A coil suppression diode, such as a Curtis PMC p/n MP-1 (which is
rated at 100 volts, 3 amps) should be used on each of the forward/reverse
contactor coils.
Forward/Reverse Switches
The forward/reverse contactor coils can be operated by any type of
single-pole, double-throw (SPDT) center-off switch capable of switching
the coil current. Toggle or rocker switches are generally used.
If your controller has the optional high pedal disable (HPD) feature
and you plan to wire it for freewheeling, the best switch to use is a double-
pole, double-throw (DPDT) “hesitation switch”— a toggle switch with
a mechanism that forces it to stop in the center (neutral) position before
going into the opposite direction. If a standard switch is moved quickly
from one direction to the other, it may not be in neutral long enough to
actuate HPD, and the motor will plug brake instead of freewheeling. The
switch must be in neutral for several milliseconds to actuate HPD.
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