Generac Power Systems 53187 - Manual (Page 107)

PARTS
ENGINE ELECTRICAL SYSTEM
1
SECTION 5.1
INTRODUCTION TO DC CONTROL SYSTEMS
Section 5.1
INTRODUCTION TO DC CONTROL SYSTEMS
General
Several different variations of the engine DC con­
trol system have been employed on the NP and IM
series generators. These variations depend on (a) the
date the engine control circuit board was manufac­
tured, and (b) the type of starter used to crank the
engine. To avoid confusion between these system vari­
ations, this manual arbitrarily identifies the DC control
system as Type 1, Type 2 or Type 3.
TYPE 1 DC CONTROL SYSTEM;
The Type 1 DC control system applies to units
having an earlier production engine control circuit
board. These early circuit boards required that a crank
relay (CR1) and a run relay (CR2) be employed to
deliver operating power to the board during cranking
and running, and to open the power circuit to the board
for shutdown. Only the Type 1 system employs Relays
CR1 and CR2.
The engine starter (Part No. 70954) used on these
units is NOT equipped with a pull-in type starter sole­
noid. A starter contactor (SC) is used to deliver cranking
current to the starter motor.
TYPE 2 DC CONTROL SYSTEM;
Type 2 DC control systems utilize an improved
engine control circuit board. The crank (CR1) and run
(CR2) relays that were used in Type 1 systems are not
required, since the circuit board has taken over the
function of the relays.
Like the Type! systems, the engine starter (Part
No. 70954) is NOT equipped with a pull-in type starter
solenoid. A starter contactor (SC) is used to deliver
cranking current to the starter motor.
TYPE 3 DC CONTROL SYSTEM:
The same improved engine control circuit board
that is used on Type 2 systems is used on the Type 3
system. Crank relay (CR1) and run relay (CR2) are not
used.
The engine starter on Type 3 units IS equipped with
a pull-in type starter solenoid. A single starter relay (SR)
is employed to energize the starter-mounted solenoid
and initiate cranking.
Engine Control Circuit Board
The engine control circuit board Is the electronic
control center for engine cranking, starting, running and
shutdown operations. The circuit board is housed in the
generator control panel. Two terminal strips are pro­
vided on the board, with terminals numbered from 1
through 12. See Rgure 1.
The circuit board is powered by 12 volts DC from
the unit battery. Functions of the various terminals are
listed in the following chart.
TERMINAL WIRE FUNCTION OF CIRCUIT
1 Fused battery voltage (■•■)
2 0 Battery negative (grounded)
side of power supply circuit
3 17,17A Start circuit. Initiates startup
when start/stop switch is
set to "Start"
4 18 Shutdown circuit, initiates
shutdown when start/stop
switch Is set to "Stop"
5 11 Engine speed (frequency)
signal for overspeed
shutdown
6 22 Engine speed (frequency)
signal for overspeed
shutdown
7 56 Engine cranking circuit
8 9 DC voltage to field boost
9 14 Engine run circuit Is
energized when engine is
running
10 14 Same as Terminal 9
11 14 Same as Terminal 9
12 85 Provides automatic shut­
down when circuit Is
grounded by closure of
low oil pressure switch or
high coolant temperature
switch
Figure 1. Engine DC Control Circuit Board
PAGE 5.1-1