Curtis PMC 1204X/1205X/1209/1221 Manual
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GLOSSARY
Pot fault
See Throttle pot fault protection.
PTC
A PTC (Positive Temperature Coefficient) resistor is a resistive element that
changes value depending on its temperature. At low temperatures, it has a very low
resistance value. As current flows through the PTC, it heats up and at a certain
temperature it trips to a higher resistance value. PTCs are used on the keyswitch,
forward, and reverse controller inputs to improve performance in freezer and
moisture-intensive environments. Their addition increases the standby current to
approximately 250 mA on 12V models and 100 mA on 24–36V models.
PWM
PWM (Pulse Width Modulation), also called “chopping,” is a technique that
switches battery voltage to the motor on and off very quickly, thereby controlling
the speed of the motor. Curtis PMC 1200 series controllers use high frequency
PWM—15 kHz—which permits silent, efficient operation. PWM is described in
more detail in Appendix B.
Smooth, stepless operation
Like all Curtis PMC 1200 Series controllers, 1204X/1205X/1209/1221 models
allow superior operator control of the vehicle’s drive motor speed. The amount
of current delivered to the motor is set by varying the “on” time (duty cycle) of
the controller’s power MOSFET transistors. This technique—pulse width modu-
lation (PWM)—permits silent, stepless operation.
Static return to off (SRO)
[OPTIONAL FEATURE]
The SRO feature prevents the vehicle from being started when “in gear.” If the
operator attempts to start the vehicle while in forward or reverse, the controller
(and the vehicle) will remain off. For the vehicle to start, the controller must
receive an input to KSI from the designated SRO interlock before receiving a
forward or reverse input from the forward/reverse switch. Like HPD, this safety
feature ensures smooth starts.
The 1204X/1205X/1209/1221 controllers are available either with or with-
out the SRO feature.
Temperature compensation
Internal temperature compensation ensures that the controller’s current limit
remains constant over varying controller temperatures. This eliminates perfor-
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