A-6
Curtis 1207B Manual
2 9 J U N E 2 0 1 2 D R A F T
APPENDIX A: GLOSSARY
The operating PWM frequency is shifted to 1.5 kHz when the controller is
operating in the overtemperature range.
Overvoltage protection
Overvoltage resets the microprocessor, inhibits PWM, and opens the contac
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tors, thereby shutting down the controller. Overvoltage can result during bat
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tery charging or from an improperly wired controller. Controller operation
resumes when the voltage is brought within the acceptable range. The cutoff
voltage and re-enable voltage are percentages of the battery voltage, and are
set at the factory.
Plug braking
Plug braking takes place when a series motor is driven electrically in a direction
opposite from the direction it is turning. The 1207B controls the field current
to obtain smooth and controlled plug braking torque. During plug braking,
the maximum current limit is automatically changed to the plug current limit,
and the PWM frequency is changed to 1.5 kHz. Note: Plug current limit on
the 1207B controls the
field current. The armature current in plug mode will
be higher than the field current.
There are two types of plug braking control — fixed and variable. The fixed
plug current limit is set to a fixed level. The variable plug current limit varies
the current limit to correspond to the throttle position.
The plug current limits in Mode 1 and in Mode 2 are independently ad
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justable via the handheld programmer.
PWM
Pulse width modulation (PWM), also called “chopping,” is a technique that
switches battery voltage to the motor on and off very quickly, thereby control-
ling the speed of the motor. Curtis 1200 series controllers use high frequency
PWM—15 kHz—which permits silent, efficient operation.
Quick-start
Upon receiving a quick throttle demand from neutral, the controller will exceed
normal acceleration momentarily in order to overcome inertia. The “quick-
start” algorithm is applied each time the vehicle passes through neutral and is
not in plug mode. If the vehicle is in plug, the quick-start function is disabled,
allowing normal plug braking to occur.
The quick-start throttle factor is adjustable via the handheld programmer.
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