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Curtis PMC 1204X/1205X/1209/1221 Manual
Controller fault protection
Faults can be caused internally (e.g., failed electronic components) or externally
(e.g., wrench dropped across controller terminals). When a fault is detected, the
controller's forward/reverse and bypass contactor outputs are turned off.
Faults are detected by monitoring the controller's M- output. M- should
periodically go high; if it remains low for more than 20 ms, a fault is detected.
Fault protection is disabled for throttle input greater than 80%; this prevents full
speed and normal bypass mode from being detected as faults.
To recover from a fault, the forward/reverse switch must be turned off and
back on again. For controllers with SRO, the SRO sequence must be initiated.
If the fault has been corrected, the controller will turn back on.
Current limiting
Curtis PMC controllers limit the motor current to a preset maximum. This
feature protects the controller from damage that might result if the current were
limited only by motor demand.
In addition to protecting the controller, the current limit feature also
protects the rest of the system. By eliminating high current surges during vehicle
acceleration, stress on the motor and batteries is reduced and their efficiency and
service life are improved. Similarly, there is less wear and tear on the vehicle
drivetrain, as well as on the ground on which the vehicle rides (an important
consideration with golf courses and tennis courts, for example).
The maximum motor current can be factory-set to a lower value than the
standard maximum, if requested. In addition, the current limit is field adjustable
(see Section 4).
Current multiplication
During acceleration and during reduced speed operation, the Curtis PMC
controller allows more current to flow into the motor than flows out of the
battery. The controller acts like a dc transformer, taking in low current and high
voltage (the full battery voltage) and putting out high current and low voltage.
The battery needs to supply only a fraction of the current that would be required
by a conventional controller (in which the battery current and motor current are
always equal). The current multiplication feature gives vehicles using Curtis PMC
controllers dramatically greater driving range per battery charge.
Emergency reverse
Emergency reverse ("belly-button") switches can be mounted on the handles of
walkie vehicles. The emergency reverse switch is wired to the controller, reverse
contactor, and throttle pot in such a way that if the button is pressed against the
[OPTIONAL FEATURE]
GLOSSARY
37
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