Curtis PMC 1204X/1205X/1209/1221 Manual
39
GLOSSARY
MOSFET
A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a type of
transistor characterized by its fast switching speeds and very low losses.
Overtemperature
See Thermal protection.
Overvoltage cutoff
Overvoltage cutoff inhibits the PWM and opens the contactors, preventing
operation when battery voltages are too high for proper functioning. This protects
the controller and motor from possible damage due to the overvoltage condition.
Overvoltage can result during battery 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
The vehicle can be braked electrically by selecting the opposite direction with the
forward/reverse switch without releasing the throttle. When the motor is reversed,
the armature acts as a generator; the controller regulates the current in the motor
field winding to give an appropriate level of plug braking torque. The vehicle
brakes smoothly to a stop, then accelerates in the other direction. (NOTE: The
controller may be unable to provide plug braking if the vehicle is moving too
slowly for the motor to generate the necessary plug braking current.)
The plug current limit is factory set to meet customer requirements. In
addition, the plug current limit is adjustable via an externally accessible trimpot;
see Section 4 for adjustment instructions.
Two types of plug braking control are available: variable and fixed. Variable
plug braking allows the amount of plug braking to be adjusted via the throttle.
When direction is reversed, the plug braking current increases as a function of the
throttle position. Maximum plug braking will occur at maximum applied throttle.
Fixed plug braking, on the other hand, applies the specified amount of braking
when the direction is reversed regardless of the amount of throttle applied.
If plug braking is not desired, the vehicle can be wired so that moving the
forward/reverse switch through neutral causes the vehicle to freewheel as long as
the accelerator is applied. If the throttle is released and reapplied, plug braking
will then occur. To inhibit plug braking in this way, your controller must have
the optional HPD feature. Wiring details are provided in Section 3.
A 1 kHz tone may be heard during plug braking. This noise is normal and
indicates that plugging is taking place. The noise will stop when the plug braking
stops.
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