Guardian 4721, Руководство по ремонту

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PREPACKAGED LIQUID
COOLED AC GENERATORS
SECTION 2.1
DESCRIPTION AND MAJOR COMPONENTS
PART 2
Page 23
Figure 6. Prepackaged Voltage Regulator
If the red LED goes “out”, sensing signals to the regu-
lator have been lost. The following rules apply:
• Loss of sensing can be caused by an “open” circuit
condition in sensing leads S15 and S16. These
sensing leads also operate the generator’s panel
mounted AC frequency meter. Thus, if the red LED
is out, it may be assumed that an open circuit exists
in the sensing circuit.
• Loss of sensing to the regulator will usually result in
a “full field” condition and resultant high voltage out-
put from stator AC power winding. The maximum
voltage that regulator action can deliver is limited by
a “clamming” action on the part of the regulator.
• A complete open circuit condition in the stator AC
power windings will cause loss of sensing voltage
and frequency. However, this will result in a zero
voltage output from the stator windings.
Based on the “sensing” signals, the regulator delivers
direct current (DC) to the rotor, via Wire No. 4 and the
positive (+) brush and slip ring. This regulated current
flows through the rotor and to frame ground, via the
negative (-) slip ring and brush and Wire No. 1. The
following apply:
• The concentration of magnetic flux lines around the
rotor will be proportional to the regulated excitation
current flow through the rotor plus any residual
magnetism.
• An increase in excitation current flow through the
rotor windings will increase the concentration of
“magnetic flux” lines around the rotor which, in turn,
will increase the AC voltage induced into the stator
AC power windings.
FIELD BOOST
See Figure 7. The prepackaged system provides a
“field boost” feature. Field boost, in effect, “flashes the
field” whenever the engine is cranking to ensure an
early “pickup voltage” in the stator windings.
A field boost diode and a field boost resistor are
installed in a printed circuit board. Field boost DC out-
put to the rotor is reduced to approximately 9-10 volts
by the field boost resistor.
Manual and automatic cranking is initiated by PCB
board action, when that board energizes a crank relay
(K1). When the relay is energized, battery voltage is
delivered across its closed contacts and to the rotor,
via a field boost resistor, field boost diode, and Wire
No. 4. Notice that field boost current flow is available
only while the engine is cranking.
Figure 7. The Field Boost Circuit
(from Schematic Drawing #0F5244)
4
RED
4
AR
1
1
4
0
4
0
VR
PCB
15
17 A B
14
16
4
3
E
12
5 13 1 2 7 D 11 9 10
S15
S16
0
4
4
6
162