Hill-Rom VersaCare P3200, Service Manual

Page: 120 / 379

Electrical System
Chapter 3: Theory of Operation
air solenoid power, and AC air pump power. Secondary 1 fuse is a 20 A, 250
V, TD, UL. Secondary 1 has a 25% duty cycle. Secondary 2 provides battery
charge power, logic power, IntelliDrive® Transport System charge power.
Secondary 2 is rated at 28 Vrms @ 6.5 Arms with < 4% regulation. Secondary
2 has a 100% duty cycle.
For ESD immunity the system ground (Vss) is not connected to earth ground.
The batteries are 7.2Ahr connected in series for 24 VDC. The battery fuse is
15A, 250V, FB, UL, 3AB.
VMOT_UR
VMOT_UR (21.5 - 35 VDC, 24 VDC @ 12 A) is derived from secondary 1
full wave rectified by the external 35A bridge and filtered by the 68000uF
external capacitor. Resistor, R3, discharges the filter capacitors when AC
power is removed. Maximum discharge time is 4 minutes. Relay, K1, provides
isolation between VBAT and VMOT_UR. The microprocessor will close the
relay when on battery power.
VLOG_UR
BR1 and C38 provide the conditioning for VLOG_UR (30 - 46 VDC, 36 VDC
@3.5 A).
Air Pump
The circuitry of RT5, Q6, U2, Q10, and P4 provide switched AC power for the
air pump. The pump draws 3Arms maximum. The circuitry around U1 detects
if power is available for the pump or not. The nominal voltage of the pump is
21 V AC.
Battery Charger
The circuitry around RT4, K3, Q2, Q3, R100, and D6 make up the high current
parts of the battery charger. Relay, K3, is a supervisory switch for the charger.
The charge voltage and current are regulated by Q2 via Q3. Resistor, R1, is
used to sense the charge and discharge current. R12 and R15 provide a scaled
voltage for the A to D to read.
MISC
Half of D6 is used for reverse battery protection along with the battery fuse.
Page 3 - 6 VersaCare™ Bed Service Manual (MAN333 REV 2)