Guardian 4721, Руководство по ремонту

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board. If voltage at the terminals is zero or low, stand-
by generator startup and transfer to the “Standby”
source will occur automatically as controlled by the
control board. A zero or low voltage at these terminals
will also prevent retransfer back to the “Utility” source.
PROCEDURE:
With utility source voltage available to Terminal Lugs
N1 and N2, use an AC voltmeter or a VOM to test for
utility source line-to-line voltage across terminal block
“Utility 1” and “Utility 2” terminals. Normal line-to-line
utility source voltage should be indicated.
RESULTS:
1. If voltage reading across the “Utility I” and “Utility 2” termi-
nals is zero, go to Test 10.
2. If voltage reading is good, go to Test 9.
TEST 9 - CHECK VOLTAGE AT UTILITY
CLOSING COIL C1
DISCUSSION:
Utility source voltage is required to energize utility
closing coil C1 and effect retransfer back to the
“Utility” source. This voltage is delivered to the utility
closing coil via Wires No. N1A and N2A, the transfer
relay’s normally-closed contacts (relay de-energized),
Wire No. 126, limit switch XA1, and a bridge rectifier.
PROCEDURE:
1. On the generator control panel, set the AUTO-OFF-MAN-
UAL switch to OFF.
2. Turn OFF the utility power supply to the transfer switch,
using whatever means provided (such as a utility source
main line circuit breaker).
3. Set the generator’s main line circuit breaker to its OFF or
“Open” position.
4. Check the position of the transfer mechanism main con-
tacts. The moveable load contacts must be connected to
the stationary utility contacts. If necessary, manually actu-
ate the main contacts to their “Utility source side (load
connected to the “Utility” source).
5. Set the generator’s main line circuit breaker to its ON or
“Closed” position.
6. Set the generator’s AUTO-OFF-MANUAL switch to AUTO.
a. The generator should crank and start.
b. About 15 seconds after engine startup, the
transfer relay should energize and transfer to
the “Standby” source should occur.
7. When you are certain that transfer to “Standby” has
occurred, turn ON the utility power supply to the transfer
switch. After a short wait, retransfer back to the “Utility”
source should occur.
8. If retransfer back to “Utility” does not occur, use an AC
voltmeter (or a VOM) to test the voltage across the two
terminals of the utility closing coil. Normal utility source
line-to-line voltage should be indicated.
RESULTS:
1. In Step 6, if the generator does not crank or start, refer to
Part 4, “DC Control - Units with Liquid Cooled Engine”.
2. In Step 6, if transfer to the “Standby” source does not
occur, go to Problem 1.
3. In Step 8, if normal utility source line-to-line voltage is
NOT indicated, go to Test 3.
4. In Step 8, if normal utility source line-to-line voltage is
indicated but retransfer back to “Utility” does not occur, go
to Test 4.
TEST 10 - CHECK FUSES F1 AND F2
DISCUSSION:
Fuses F1 and F2 are connected in series with the
Utility 1 and Utility 2 circuits, respectively. A blown
fuse will open the applicable circuit and will result in
(a) generator startup and transfer to “Standby”, or (b)
failure to retransfer back to the “utility” source.
Figure 5. Fuse Holder and Fuses
N1A N2A T1A T2A
N1
N2 N1
N2
F1
F2
F4
F3
PART 3
Page 54
“V-TYPE” PREPACKAGED
TRANSFER SWITCHES
SECTION 3.4
DIAGNOSTIC TESTS