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C. Hobart Engine Equipment
The engine is modified at Hobart Brothers by the addition of the following equipment:
(1) Electric governor system
An electric governor kit is installed on the engine to replace a conventional, mechanical type.
The electric governor was selected for control of engine speed (and generator output fre-
quency) because it provides faster engine response to changes in load conditions. This fast
response results in very close frequency control. Refer to the Barber Coleman Handbook in
Chapter 6 for a detailed description. A brief description is given below:
The governor system consists of the following main components:
Magnetic pickup
Control unit
Actuator
(a) Magnetic pickup
The magnetic pickup is a device for detecting the speed of the engine. It is mounted in
the flywheel housing directly over the ring gear. It produces an AC signal to the control
unit when the ferrous flywheel teeth pass through the magnetic field at the end of the
pickup.
(b) Control unit
The control unit (5, Fig. 3) is a box containing a compact assembly of solid state compo-
nents. It receives an AC signal from the magnetic pickup and senses speed changes in
the engine. It provides a voltage signal to the actuator which causes the actuator to move
the fuel control lever as required to maintain a predetermined engine speed. Its power is
received from the 12-V DC battery system.
(c) Actuator
The actuator (12, Fig. 3) supplies the force needed to move and position the fuel lever as
required to maintain a constant engine speed. The actuator is operated by a DC signal
from the control unit.
(2) Engine electrical system
Items in the 12-volt engine electrical system that are provided by Hobart Brothers are:
(a) A heavy-duty motor starter
(b) Alternator with voltage regulator
(c) Starting switch
(d) Wiring harness
(3) Engine protective devices
(a) High coolant temperature switch
A high coolant temperature switch is mounted in the front of the cylinder block to monitor
the coolant temperature. If the coolant temperature reaches 210 degrees F (99 degrees
C) , this normally closed switch opens and actuates the fuel valve solenoid which shuts
down the engine.
April 30/96 Revised
OM-2031
1-1
Page 9
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