Chapter 1. Description/Operation; Section 1. Description; General; Orientation - Hobart 60PL20 Operation And Maintenance Manual

CHAPTER 1. DESCRIPTION/OPERATION

SECTION 1. DESCRIPTION

1. General

This manual covers two trailer-mounted 60-kVA generator sets manufactured by Hobart Brothers Com-
pany and identified respectively as Specification No. 7009-1, Specification No. 7009A-1, and Specifi-
cation No. 7009B-1
All three generator sets feature an armature with Hoover Bearings, Browning Coupler, and different mag-
netic pole construction for the generator revolving field. This new armature can be easily identified by two
copper rings on each end of the field coils and copper wedges between magnetic poles.
The difference between Specification No. 7009-1and Specification No. 7009A-1 is that Specification No.
7009A-1 features new-style doors on the canopy assembly. Specification 7009B-1 is physically and electri-
cally identical toSpecification 7009A-1, except that a Barber-Colman engine speed governor is used in-
stead of the Woodward governor used on Specification No. 7009-1and Specification No. 7009A-1.
The purpose of these generator sets (Fig. 1) is to generate and deliver regulated, 400-Hz electrical power
to a parked (or towed) aircraft for operation of the aircraft's electrical equipment when the on-board gener-
ators are not running. See Figure 2 for specifications and capabilities.

2. Orientation

For purpose of orientation and to familiarize operators and maintenance personnel with the location of
components, the radiator is considered to be at the FRONT of the unit. The generator and controls are at
the REAR. RIGHT and LEFT are determined by standing at the rear end facing the machine.

3. Special Features

These generator sets have many special features which are later described more fully under the assem-
blies in which they appear. Some of the main features are mentioned here and described briefly.
A. Protective Monitor
A single, solid-state device (7, Fig. 7) receives signals from all of the fault sensing units in the gener-
ator output circuit and functions to cause the load to be disconnected from the generator if an abnor-
mal condition of voltage, frequency, or load develops.
B. Voltage Regulator
A solid-state, adjustable voltage regulator (Items 13 and 17, Fig. 7) provides automatic voltage regula-
tion at the aircraft (or distribution panel when applicable). The regulator is also adjustable for a variety
of output cable sizes and lengths.
C. Electric Governor
The engine is equipped with an all electric type governor kit (13 and 16, Fig. 3) and other special
equipment more fully described under the engine description.
December 31/91 Revised
OM-2053
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