Generator; Rectifier Assembly; Ammeter Shunt; Contactor K402 - Hobart Jet-Ex 5D Operation And Maintenance Manual

OM-2094 / Operation and Maintenance Manual
Jet-Ex 5D / Series 500285 / Generator Set
c. Generator
The generator (5, 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 (4) made up of twelve
rectifiers connected into a full wave configuration. The generator is self-excited, receiving 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 flows over the rectifier assembly (4, Figure 2) and then enters through the anti-drive end of the
generator and is discharged through openings in the flywheel housing at the drive end. The
generator housing assembly, which contains the generator stator, is bolted to the engine flywheel
housing.
d. Rectifier Assembly
The Rectifier Assembly (4, Figure 2) consists of two aluminum heat sinks with six diodes on each
heat sink. The rectifier assembly converts the AC output of the generator to 28.5 Volts DC.
e. Ammeter Shunt
The ammeter shunt is connected in the generator's negative output circuit. It supplies a small
voltage proportional to output current for operation of the AMMETER (4, Figure 5), and to the
current limit circuit of the voltage regulator (2, Figure 6). This shunt is mounted on the negative heat
sink of the rectifier assembly (4, Figure 2).
f. Contactor K402 (10, Figure 2)
The load contactor, which is mounted on the right side of the unit below the fuel tank, provides a
safe and convenient means of connecting and disconnecting the generator from the load. Initial
power for closing the load contactor is supplied by the generator through the spring-loaded
momentary contacts of the CONTACTOR CONTROL toggle switch (7, Figure 5). Holding power, to
keep the contactor closed, passes through the normally open auxiliary contacts in the load
contactor. Output power connection is made by attaching the positive lead to the top terminal of the
load contactor, and the negative lead to the negative output terminal located above the load
contactor.
November 1, 2000
Revised 07/01
Chapter 1-1
Page 9