Thermo King SGCO 3000, Руководство пользователя

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Alternator Operation and Diagnosis
120
voltage suppression device. When
measured it will show open, it closes with
peak voltage more than 600V cannot test.
c. Check each diode in the forward and
reverse direction. Good diode will have a
high resistance reading in one direction
and no reading when ohmmeter leads are
reversed.
3. Rotating Exciter Armature
a. With the armature leads still disconnected
from the diodes, test between the
following pairs of leads. CR6-CR4,
CR3-CR1, CR3-CR2, CR6-CR5,
CR5-CR4, CR2-CR1. The resistance
between any of the pairs should be 0.645
(±10%) ohms at 25 C (77 F).
b. Using a megger meter, check for
insulation break down between each pair
of leads to the rotor shaft. @ 500 Volts
must be more than 1 M ohm.
Figure 98: Exciter Armature
4. Rotating Field Armature
a. Measure the resistance of the main field
armature leads. The resistance should be
2.5 (±10%) ohms.
b. Using a megger meter, check for
insulation break down between the leads
to the rotor shaft. @ 500 Volts must be
more than 1 M ohm.
Megohmmeter
The use of a megohmmeter can be a valuable
addition to the repair and maintenance of the
generator set. The megohmmeter is essentially a
high-range resistance meter (ohmmeter) with a
built-in direct-current generator. This meter is of
special construction with both current and voltage
coils-enabling true ohms to be read directly,
independently of the actual voltage applied.
The meter gives you a direct reading of insulation
resistance in “ohms” or “megohms” (1 megohm =
1,000,000 ohms). For good insulation, the
resistance usually reads in the megohm range.
Normally, good insulation has high resistance;
poor insulation, relatively low resistance. The
actual resistance values can be higher or lower,
depending upon such factors as the temperature or
moisture content of the insulation (resistance
decreases with increase in temperature or
moisture). They can be quite different for a
generator tested three days in a row, yet not mean
bad insulation. What really matters is the trend in
readings over a time period, showing lessening
1. Main Field
2. Exciter Rotor
3. Exciter Field
4. Ohmmeter
Figure 99: Main Field Winding
AXA0324