Guardian 4721, Руководство по ремонту

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PREPACKAGED LIQUID
COOLED AC GENERATORS
SECTION 2.4
DIAGNOSTIC TESTS
PART 2
Page 37
TEST PROCEDURES:
TEST 13A, TEST 13B, TEST 13C, TEST 13D, check
position of the frequency switch.
TEST 13A
(Check DC Voltage Supply to Control Module)
If the control module loses the 12 volt DC input, it will
no longer be able to control or move the stepper
motor. If this happens while the unit is under a load,
an “overspeed” condition could occur as soon as the
load is removed. The stepper motor could remain in a
position supplying too much fuel for the “no load” con-
dition.
TEST 13B
(Check AC Frequency Input to Control Module)
Similar to the control module losing it’s DC input, the
control module will no longer be able to control the
stepper motor if the frequency sensing input is lost.
The stepper motor’s inability to move or react proper-
ly could result in an “overspeed” condition.
To check frequency sensing input, run unit while
manually controlling speed at a safe level. Ensure
that the unit is providing AC output.
Check the condition of the wires and connections on
“blue” sensing leads between the main circuit breaker
and the control module.
TEST 13C
(Check connections between Control Module and
Stepper Motor)
There are two “Plug-In” connectors housed inside the
connection boxes in the harness between the control
module and the stepper motor. Remove the covers
from the boxes and carefully inspect the connections.
TEST 13D
(Test Stepper Motor)
A defective stepper motor can cause overspeed, low
speed, or no-start, hard start or erratic operation.
NOTE: It is difficult to perform an operational test
on the Stepper Motor since the control voltages
vary, and motor rotational movement is so small.
If a defective stepper motor is suspected, the wind-
ings can be tested for resistance, open circuits, and
shorts to ground. (See Figure 9) for schematic and
resistance values. Any other readings other than
those which are indicated, including continuity to
ground, indicates a faulty stepper motor.
CONTROL MODULE
A detailed adjustment procedure for the Control
Module begins on Page 99.
If problems still persist after all the previous tests and
adjustments have been completed, it is recommend-
ed to then replace the Control Module and adjust as
necessary
Figure 9. Schematic and Resistance Values
YELLOW
OR
RED
RED
(NOT USED)
RED
ORANGE
OR
BLACK
BLACK
OR
GREEN
BROWN
OR
WHITE
10 OHMS 10 OHMS
10 OHMS 10 OHMS
* Measure resistance across any combination of orange, yellow, brown, or black should read approximately 20 OHMS.
* Measure from red to any other lead should read 10 OHMS.
* Testing from any lead to stepper motor case should read INFINITY.