CUMMINS QST30 - High Ac Voltage Shutdown

4-36
Copyright  2017 Cummins Inc.
TABLE 4-26A. HIGH AC VOLTAGE SHUTDOWN (301)
WARNING
Many troubleshooting procedures present hazards that can result in severe personal inju-
ry or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery haz-
ards should perform service procedures. Review Important Safety Instructions page.
Indicator(s) Possible Cause Corrective Action
“HIGH AC
VOLTAGE ”
shutdown
(301)
message.
1. The problem may be in the PCC, the
alternator, or the interconnection be-
tween them.
Note 1: The PCC may indicate either
a low AC Voltage or High AC Voltage
shutdown due to the design of the
logic in the control.
You must first determine if the out-
put voltage the control sees is low
or high.
Note 2: Residual voltage is normally
5 to 10% of nominal output voltage.
For example, a generator set with a
480 volt output, will have a residual
voltage of 25 to 50 VAC at normal
operating speed.
1. Set the display on the PCC to GEN, VOLTS,
L-N.
a. Start the generator set and observe the volt-
age displayed on the digital display.
b. If all phases of voltage are balanced and not
zero, but lower than normal, the alternator
and the input to the PCC are OK. The prob-
lem is in the excitation circuit for the alterna-
tor. Go to step 2.
c. If one or more phases of voltage are high or
the voltages are unbalanced, the PCC is not
measuring all phases of voltage and is re-
sponding to the low “average” of the three
phases of voltage. Go to step 3.
2. The problem may be the regulator
module (A37), the engine interface
board (A31), or the digital board (A32).
2. With DC power to the PCC and with the genera-
tor set not running, check A31 DS9, the AVR
duty cycle LED. this LED should be off. If it si on,
go to step 2d.
Isolate the generator set output from the load.
Disconnect A37 J10, and place the generator
set in Idle mode. In Idle mode the excitation cir-
cuit is disabled. Start the generator set and
monitor the AC output voltage with a digital
multimeter.
a. If output voltage is greater than residual (5%
of normal output), go to step 3.
b. If output voltage stays at 0 (or residual), and
DS2 on A37 is off, go to step 4.
c. If output voltage stays at 0 (or residual), and
DS2 on A37 is on, look at DS9 on A31.
If DS9 on A31 is off, replace A37.
d. If DS9 on A31 is on, connect a breakout con-
nector at A32 J4, and open J4-2.
If DS9 goes out, replace A32.
If DS9 stays on replace A31.
*CAUTION: Wearing a wrist strap, set S12 to Off and A32 S5 to Standby before connecting/disconnecting harness plugs.
(Continued)