Generac Power Systems NP-40G - Manual (Page 65)

Section 3.6- SPEED CONTROL SYSTEM
General
The AC generator’s output voltage Is controlled
by a “computerized" speed control system. This
system changes engine speed In response to
changes In the AC output voltage at varying engine
loads. The speed control system consists of (a) the
CCG circuit board and (b) a stepper motor.
CCG Circuit Board
This circuit board utilizes a closed-loop, propor­
tional-derivative controller circuit which regulates
the generator’s RMS voltage by changing engine
speed. The system attempts to maintain an output
voltage of about 115 volts at the lowest rpm and 120
volts up to the maximum rpm.
The system also Includes a controller which will
hold the engine at maximum speed. In this mode,
the system will attempt to maintain an output volt­
age of 105-115 volts.
The CCG circuit board controls a stepper motor
by calculating the number of steps the motor needs
to take and then supplying the necessary signals
to the motor to take those steps.
NOTE: Also see "CCG Circuit Board" on Pages
1.2-4 through 1.2-6.
Stepper Motor
See "Stepper Motor" on Page 1.1-2.
Testing the CCG Circuit Board
See "Testing the CCG Circuit Board" on Pagel .5-
4 and 1.5-5.
Stepper Motor Probiems
INTRODUCTION:
Some stepper motor problems that might occur
Include the following:
n Throttle linkage or carburetor throttle shaft sticking,
or linkage disconnected.
D Stepper motor failed or seized.
□ Electrical connections to stepper motor broken or
disconnected.
D Electrical leads to stepper motor are connected
wrong.
THROTTLE LINKAGE:
Check throttle linkage and carburetor throttle
shaft for binding, disconnected linkage. This type
of problem will usually result in the carburetor
throttle lever not moving. If the throttle lever does
. not move, the throttle may be stuck at a perma­
nently open throttle or a permanently closed throt­
tle as follows:
1. If the throttle is open, engine will start but will acceler­
ate quickly and uncontrollably. It will shut down when
speed exceeds about 4500 rpm.
2. If the throttle Is closed, engine will not accelerate under
load. After about 10 seconds, generator AC output will
terminate.
STEPPER MOTOR FAILED OR SEIZED:
The engine will start but stepper motor will not
turn. If an open throttle condition exists, either of
the following might occur:
1. Engine may accelerate and shut down at 4500 rpm.
2. Engine may shut down after 15 seconds due to an
overvoltage condition.
If throttle is closed, engine will be unable to
accelerate under load and AC output will be lost
after 10 seconds.
A failed stepper motor may also turn erratically.
If this Is the case, engine speed and AC output
voltage will be erratic under constant load.
ELECTRICAL CONNECTIONS BROKEN:
If one or more of the electrical connections to the
stepper motor are broken or disconnected, either
of the following might occur:
1. The stepper motor may not turn at all.
2. The stepper motor may turn erratically.
If the stepper motor does not turn, symptoms will
be the same as for a failed or seized stepper motor.
LEADS CONNECTED WRONG:
Incorrectly connected electrical leads to the
stepper motor can result In any one of the follow­
ing:
1. Stepper motor may not turn at all.
2. Stepper motor may turn erratically.
3. Stepper motor may turn backwards.
If the stepper motor does not turn, engine will start and
the following may occur:
1. If throttle Is open, engine will accelerate and shut down
when speed reaches 4500 rpm or after 15 seconds due
to overvoltage condition.
2. If throttle Is closed, generator AC output will terminate.
If the stepper motor turns erratically, engine speed and
AC output voltage will be erratic under a constant load.
The AC output will not terminate.
If the stepper motor Is turning backwards, engine will
accelerate and shut down at 4500 rpm.
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