Curtis PMC 1209B/1221B/1221C/1231C Manual
10
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 Figures
7 and 8. A heavy-duty single-pole, single-throw (SPST) contactor with silver-
alloy contacts is recommended, such as an Albright SW200 (available from
Curtis).
A coil suppression diode should be used on the contactor coil. Curtis PMC
p/n MP-1 (which is rated at 100 volts, 3 amps) is appropriate in systems up to
72V. In systems with nominal voltage greater than 72V where the contactor coils
are energized from the battery pack, a diode with a breakdown voltage of at least
200 volts should be used.
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 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.
The recommended precharge resistance values and power ratings are listed
in Table 1. These resistors will provide the maximum precharge voltage while
being capable of dissipating the power generated by the full battery voltage
without failure. NOTE: A resistor with a lower power rating may catch on fire if a
system fault applies the full battery voltage across it.
Table 1 RECOMMENDED PRECHARGE RESISTORS
CONTROLLER RESISTANCE POWER RATING
MODEL NUMBER (Ω) (W)
1209B -46XX 270 5
-55XX 270 10
-64XX 620 10
-6A5XX 620 10
-72XX 750 20
1221B -48XX 270 5
-57XX 270 10
-66XX 620 10
-6A7XX 620 10
1221C -74XX 750 20
1231C -77XX 750 20
-86XX 750 25
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