Hill-Rom VersaCare P3200, Service Manual

Page: 129 / 379

Electrical System
Chapter 3: Theory of Operation
more than a minute or so, self-resetting fuses (PTCs) interrupt the power
connection to the motor controller. As with the switch opening, the motor
controller will bring the drive motor to a stop. To manually push the bed in
either of these circumstances, the drive wheel can be stowed or the manual
override switch can disconnect the motor from the short to release the brake.
Upon sufficient cool off time for either the thermal switch to close or the PTCs
to reset, if the override switch is closed, power assist can be resumed.
Battery Shut-off
The gas gauge chip monitors the battery voltage. When the chip detects the
battery at its end of discharge voltage, the logic de-energizes the battery
connect relay. This disconnects the battery to prevent it from further
discharging.
Also, the PACM includes an input for a manual shut-down switch. If this
switch is closed for approximately 6 seconds, the shut-down logic is armed.
Opening the switch causes the logic to de-energize the battery connect relay.
This disconnects the battery from the electronics. In the event of a stuck shut-
down switch, that is, one failed closed, the logic will be armed but never
triggered, preventing nuisance shut-downs.
Deployment Motor
The deployment motor is a 24 VDC linear actuator with internal normally
closed limit switches to indicate full travel in the extended and the retracted
position. The motor circuit is separate from the limit switch circuit so that the
driver circuit can shunt the motor to provide higher holding force. The logic
can monitor the limit switches to correctly control the driver circuit.
Drive Motor
The drive motor is a 24 VDC, insulation class H, permanent magnet gear
motor producing approximately 180 in-lb. of torque at 35A. The drive motor
incorporates a Klixon®
1
YS11 style thermal switch attached to the inside of the
motor housing and characterized to open if the temperature of the motor
housing reaches 2012 °F (1100C). This temperature was chosen to track the
motor winding at a safe operating temperature.
Battery Capacity Indicator
The battery capacity indicator contains one amber LED to indicate bed power
applied or an energized battery relay and five green LEDs to indicate the
1. Klixon® is a registered trademark of Texas Instruments, Inc.
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VersaCare™ Bed Service Manual (MAN333 REV 2) Page 3 - 15