Page 20 - EASA_AR100-2020 APEX_IESCO_Neat

Section 4, Page 3 EASA AR100-2020 Recommended Practice - Rev. August 2020

4.2.8 Phase Balance Test (3) Measurement and analysis of the magnetic
The phase balance test applies balanced reduced field along the circumference of the rotor with
voltage 3-phase power to the stator and the current current applied to the rotor cage via induction
is measured and checked for balance. or direct connection to the end rings.
4.2.9 Polarity Test Caution: The use of shaft clamps can result in stray
DRAFT
current paths that reduce the effectiveness of the test
The polarity test applies direct current, usually to
a single phase, and the magnetic polarity of the coil and can affect the physical condition of the rotor or
groups are checked. shaft.
4.3.3 Armature Windings
4.2.10 Dummy Rotor Test
The dummy rotor test uses an artificial rotor such An insulation resistance test should be performed.
as a small rotor with a loose fit on a shaft. Reduced In addition, one or more of the following tests should
voltage 3-phase power is supplied to the stator and be performed:
the rotor is moved circumferentially along the bore (1) Growler test.
to check for continuous rotor rotation. (2) Winding surge test.
(3) Bar-to-bar test.
4.2.11 Impedance Test
4.3.4 Shunt, Series, Interpole,
The impedance test applies an AC voltage to the
Compensating and Synchronous
two leads of a coil and the voltage and current are
Rotor Windings
measured. Using Ohm’s Law the impedance is calcu-
lated. The impedance of the individual coils is then An insulation resistance test should be performed.
compared for relative equality among coils that are In addition, one or more of the following tests should
intended to have equal electromagnetic qualities. be performed:
(1) Winding resistance test.
4.3 RECOMMENDED WINDING TESTS
(2) Winding surge test.
Windings should be tested to ensure that there are (3) AC voltage drop test.
no grounds (earth faults), short circuits, open circuits, (4) Impedance test.
incorrect connections or high resistance connections.
4.3.5 Interconnection of Windings
4.3.1 Stator and Wound-Rotor Windings
Shunt, series, interpole, compensating, and syn-
The IR, winding surge and winding resistance tests chronous rotor windings should be tested to ensure
should be performed. In addition one or more of the that the polarities and connections are correct.
following tests may be performed: Terminal and lead markings should comply with
(1) Phase-balance test. Subsection 1.6.
(2) Polarity test.
4.4 HIGH-POTENTIAL TESTS
(3) Artificial rotor (dummy rotor) test (low voltage
energization). High-potential tests should be performed on wind-
(4) Polarization index test or dielectric absorption ings and certain accessories of electrical machines at a
specified voltage. To avoid excessive stressing of the
test.
insulation, repeated application of the high-potential
(5) Insulation dissipation or power factor test. test voltage is not recommended.
(6) Turn-to-turn test. Machines to be tested must be clean and dry. Inspec-
(7) Partial discharge testing for inception and tion and insulation resistance tests with acceptable
extinction voltage levels.
Note: Per CSA C392 the resistance unbalance results should be performed before the high-potential
tests. Insulation resistance tests should be repeated
limit for random windings should be 2% from
at the completion of the high-potential tests.
the average, and 1% from the average for form
When a high-potential test is conducted on an as-
coil windings. sembled brushless exciter and synchronous machine
Note: Some concentric windings may exceed field winding, the brushless circuit components (di-
the 2% limit.
odes, thyristors, etc.) should be short-circuited (not
4.3.2 Squirrel Cage Windings grounded/earthed) during the test.
One or more of these test methods should be used High-potential tests should be successively applied
to produce currents in bars and end rings to detect a between each winding or electric circuit under test
defect in the squirrel cage: and the grounded (earthed) frame (or core) of the
(1) Growler test. machine. All other windings or electric circuits not
(2) Single-phase test. under test should be connected to the grounded

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