Elec
trical
6 - 1
Electrical
EP800AD (Acrobat™ HPU)
ELECTRICAL
Overview
This section covers the functions of the different electrical components used as well as the
theory of operation for the electrical portion of the EP800AD (Acrobat HPU). Repair and
servicing information is included for any serviceable components. Electrical schematics are
included for the 120V and 240V models of the HPU. For EP800ADs (Acrobat HPUs) with
the previous revision hydraulic manifold, refer to the section
for service
information particular to that model of the HPU.
Components and Functions
Hour Meter
Powered by a Lithium battery. Display is always “ON”, allowing for visualization of
machine run time even when power is off.
Hour Meter will display a flashing hourglass when the machine power switch is on the
ON position and internal 24VDC power is available to close the motor relay (K1).
Refer to
Electrical Schematic (719904) Sheet B
Pressure Switch
Senses system pressure. It sends a 24VDC signal to close motor relay (K1) and turn
on the motor when the system pressure is at 830 psi (+/- 10 psi). When system
pressure reaches 1350psi (+/- 10 psi), it opens motor relay (K1) and stops the
motor.
Pressure Transducer
Senses output pressure and feeds it to the electronic valve controller to ensure
pressure matches requested pressure set by the user.
This transducer is fed 24VDC and uses a 4mA – 20mA signal through the electrical
box and to the valve controller. This signal is used by the valve controller to ensure
accurate control of HPU output pressure.
Close / Open Solenoids
These solenoids are energized by 24VDC supplied directly from the electrical box.
Replace only using authorized McElroy parts.
Proportional Pressure Reducing Valve (PRV)
This valve uses 24 VDC and a pulsed width modulated signal to control carriage
pressure to the pressure set by the user.
Valve resistance is 20.9 ohm when powered off.
When not powered, the valve is closed and will produce 0 pressure.
