Curtis 1204 Manual page 43

Curtis PMC 1204/1205 Manual
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. (
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.
On some 1204/1205 models, the plug current limit is adjustable via an
externally accessible trimpot. See Section 4 for adjustment instructions.
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.
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, the 1204 and 1205 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 tech-
nique — pulse width modulation — permits silent, stepless operation.
Pulse width modulation is described in Appendix B.
Thermal protection
Because of their efficiency and thermal design, Curtis PMC controllers
should barely get warm in normal operation. Overheating can occur,
however, if the controller is undersized for its application or otherwise
overloaded. If the internal temperature of the controller exceeds 75°C
(167°F), the current limit decreases to approximately half its rated value.
: The controller may be unable to provide
NOTE
GLOSSARY
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