Chapter 1. Description/Operation; Section 1. Description; General; Orientation - Hobart 140GT17P Operation And Maintenance Manual With Illustrated Parts List

CHAPTER 1. DESCRIPTION/OPERATION

SECTION 1. DESCRIPTION

1. General

Generator sets (see Fig. 1) covered by the manual are identified by Series No. 6906. The various configu-
rations of the set are identified by adding a dash number (-1, -2, etc.) suffix to the Series number. Series
6906 generator sets feature armatures with Hoover Bearings, Browning Coupler, and different magnetic
pole construction for the generator revolving field.
The basic generator set which includes the engine, generator and all controls is identical for all models.
Differences between models are those required by their respective mountings, such as trailer mounting,
truck mounting, etc., or by other special features. Identification of different models within the Series will be
explained later in the Description. Information and instructions throughout the manual apply to all models.
Information which applies only to a certain model will be qualified and identified as such.
The purpose of the generator set 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 generators are not
running. The engine, generator, and controls are designed into a compact unit which is easily removable
from a tow tractor. 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. Thus, the
generator controls are mounted on the REAR of the unit.

3. Special Features

The generator set has many special features which are later described more fully under the assemblies in
which they appear. Some of the main features are mentioned here and described briefly.
A. Protective Monitor
A single, solid-state device (4, Fig. 8) 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 (Hobart part number 489812A) is used on Specification
6906-1 and 6906-2 generator sets. This voltage regulator provides automatic voltage regulation at
the aircraft (or distribution panel when applicable) . This regulator is adjustable for a variety of output
cable sizes and lengths. A magnetic amplifier type voltage regulator (Hobart part no. 281407) is
used on Specification 6906-3, Specification 6906-4, Specification 6906-5 and Specification 6906-6
generator sets. This regulator is also adjustable for a variety of output cable sizes and lengths.
July 27/90 Revised
OM-2029
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