C.hobart Engine Equipment; Electric Governor System; (A) Magnetic Pickup; (B) Control Unit - Hobart 60PL20 Operation And Maintenance Manual

OM-2053

C.Hobart Engine Equipment

The engine is modifiee 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 frequency) be-
cause it provides faster engine response to changes in load conditions. This fast response re-
sults in very close frequency control. Refer to the Woodward Governor manual in Chapter 6 for a
detailed description. A brief description is given below:
The governor system consists of the following main components:
(a) Magnetic pickup, (b) Control unit, and, (c) Actuator

(a) Magnetic pickup

This pickup is a device for detecting engine speed. It is mounted in the flywheel housing di-
rectly over the ring gear. It produces an AC signal to the control unit when the ferrous fly-
wheel teeth pass through the magnetic field at the end of the pickup.

(b) Control unit

The control unit (13, 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 (16, Fig. 3) supplies the force needed to move and position the fuel lever as re-
quired 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 de-energizes the fuel valve solenoid which shuts down the
engine.

(b) Oil pressure switch

A diaphragm-type switch monitors the pressure in the lubricating oil system. It is mounted in
the side of the cylinder block (9, Fig. 3) . If the pressure in the lube oil system falls to 10 psi
(69 kPa) , this switch opens and de-energizes the fuel valve solenoid which shuts down the en-
gine.
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December 31/91 Revised