Curtis PMC 1204X/1205X/1209/1221 Manual
9
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
7. 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 (rated at 250Ω, 5W), is
recommended; the resistor precharges the capacitors and reduces the inrush
current through the contacts. If an inexpensive “can” type solenoid is used, the
resistor is mandatory to prevent contact welding. For applications above 48V, a
precharge resistor with a power rating greater than 5W is recommended.
Forward/Reverse Contactors
The forward/reverse contactor coils must match the vehicle’s battery voltage. The
maximum allowed coil current for each contactor is 1 amp. Use of a changeover
contactor set—such as the Albright DC88 or DC182 (available from Curtis)—
is recommended. Alternatively, two single-pole, double-throw (2×SPDT) con-
tactors may be used. Although inexpensive “can” type solenoids may be used,
their ratings are typically not sufficient for long life.
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 millisec-
onds to actuate HPD.
Bypass Contactor
A bypass contactor can be used with controllers that have the optional bypass
contactor output feature. The bypass option is available only on 12V and 24–36V
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