Control Panel Assembly - Hobart Jet-Ex 4D Operation And Maintenance Manual

OM-2063 / Operation and Maintenance Manual
Jet-Ex 4D / Specs 7003A-3 and 7003B-3 / Generator Sets
7. Generator
The generator (9, Figure 2) is a multi-phase, synchronous salient pole, revolving field, AC generator
whose output is rectified. The output is rectified by a rectifier assembly (6) made up of twelve rectifiers
connected into a full wave configuration. The generator is self-excited and receives excitation from a
three phase full wave rectified stator winding. One positive and one negative brush in contact with slip
rings supply controlled excitation current from the stator winding through the voltage regulator to the
rotating field winding. The voltage regulator controls the excitation current and maintains a constant
output voltage. Access to the brushes is through holes in the anti-drive end bracket. The rotor is
supported at the anti-drive end (slip ring end) by a single-row ball bearing. The drive end is connected to
the engine fly-wheel by a flexible disc and hub coupling assembly and is supported by the engine main
bearings. A radial-blade fan of formed and welded sheet metal construction is mounted on the coupling
hub and draws cooling air over the generator windings.
Air enters through the anti-drive end of the generator and is discharged through openings in the flywheel
housing at the drive end, to cool the rectifier assembly above it. The generator housing assembly, which
contains the generator stator, is bolted to the engine flywheel housing.

8. Control Panel Assembly

a. General
The hinged control panel (8, Figure 2) houses and provides mounting facilities for controls,
monitoring instruments, voltage regulator, relays, etc. The panel is mounted at the rear of the
canopy. The controls are accessible behind a hinged Lexan cover.
b. Lights
Two panel lights (7, Figure 3) provide illumination for instruments and controls. One green pilot light
(12) glows when the output load contactor is closed, and another one (14) glows green when the
engine is running.
c. Monitoring instruments
The voltmeter (6, Figure 3) indicates generator output voltage, and the ammeter (5) displays
generator current.
A tachometer (2) displays the engine speed in RPM. This instrument receives its operating signal
from the alternator.
A water temperature gauge (3) indicates the engine coolant temperature and is actuated by a
temperature sender (23, Figure 2) mounted on the engine's water jacket.
An oil pressure gauge (1, Figure 3) displays the pressure in the engine's lubrication system. It is
operated by a sender (24, Figure 2) mounted on the engine block.
The ammeter (19, Figure 3) indicates the rate of charge or discharge in the engine's 12 volt DC
electrical system.
The hourmeter (15) records the total hours of engine operation for scheduling maintenance.
d. Potentiometer
The current limiting potentiometer (4) is used to select the starting current recommended for various
aircraft. The current limiting setting is continuously adjustable from 300 to 2000 amperes.
e. Switches
The contactor control switch (11, Figure 3) is a three-position toggle switch used to close and open
the output load contactor. The top CLOSE position is spring-loaded and is held momentarily until the
contactor closed light (12) glows, then it is released to the center ON
position. In this position the switch provides holding current to the load contactor to keep it closed.
Protective devices in the load contactor circuit provide protection against overvoltage by opening the
load contactor if that condition occurs. In the bottom OFF position, the contactor is opened. The
push-to-build-up-voltage switch (10) is a momentary contact pushbutton switch which flashes the
generator fields with 12 volt engine circuit when flashing the fields.
Chapter 1-2
Page 6
Dec 31/92