Special Features; Protective Monitor; Pull-Out Trays; Voltage Regulator - Hobart 6921 Series Operation And Maintenance Manual

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets

2. Special Features

The generator sets covered by this manual have many special features which are described in detail
under the assemblies in which they appear. Some of the features are as follows:T
a. Protective Monitor
A single, solid-state device (1, Fig. 3) receives signals from all of the fault sensing units in the
generator output circuit and disconnects the load from the generator if an abnormal condition of
voltage, frequency, or load develops.
b. Pull-out Trays
The control box is equipped with pull-out, drawer-type trays (15, Fig.3) which provide easy access to
controls and equipment mounted in them. Each tray may be removed as an assembly by
disconnecting a single quick-disconnect connector and tripping two safety latches.
c. Voltage Regulator
A solid-state, adjustable voltage regulator (3, Fig. 3) provides automatic voltage regulation of the
aircraft. The regulator is adjustable for a variety of output cable sizes and lengths.
d. Test Circuitry
A receptacle connector (10, Fig. 1) , with wiring to various test points throughout the electrical circuitry
is provided for the attachment of a test box manufactured by Hobart Brothers. This test circuitry
allows electricians to perform as many as twenty-four tests and checks from one location.
e. Electric Governor
The engine is equipped with an all electric type governor (4 and 16, Fig. 3) and other special
equipment described under the engine description.
f. Transformer-Rectifiers (Optional)
Generator sets covered by this manual may be equipped with one or two transformer-rectifiers (16,
Fig. 1) . A transformer-rectifier, or T-R, receives 115/200-V AC power from the generator output and
converts it to DC power for starting and maintenance of aircraft having DC electrical systems. Two
different T-R's are available for installation on generator sets covered by this manual; one with
28.5-V DC power output and another with 112-V DC power output. A generator set may be ordered
with one or two of either of these T-R's or with one 28.5-V DC T-R and one 112-V DC T-R.

3. Optional Equipment

a. Quick Start Kit
(See Para. 2, F, Item (2) (f) and Section 1-3, Para. 2, C.)

4. Canopy

A sheet metal enclosure, or canopy (8, Fig. 1) , provides protection for the engine, generator and
electrical controls. It has two large, hinged doors on each side to provide access for service and
maintenance. A large panel at the rear provides access to the air filter. A plexiglass window is mounted
in the left front door to allow observation of the instruments. The window is mounted at an angle and is
open at the bottom to permit access to the controls without opening the door.
Chapter 1-1
Page 6
February 28/94
Revised