Page 21 - EASA_AR100-2020 APEX_IESCO_Neat

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

(earthed) frame (or core). winding in the normal manner for machine operation
Capacitors of capacitor-type motors must be left (running or starting).
connected to the winding in the normal manner for Component devices and their circuits, such as space
machine operation (running or starting). heaters and temperature sensing devices in contact
Electrical machines may be tested using AC or DC with the winding (thermostats, thermocouples,
high-potential test equipment. The DC test voltage thermistors, resistance temperature detectors, etc.),
should be 1.7 times the specified AC voltage. A failure connected other than in the line circuit, should be
under test can be less damaging to the winding if a connected to the grounded (earthed) frame or core
DC voltage is used. during machine winding high-potential tests. Each
AC high-potential testing should be performed by of these component device circuits, with leads con-
applying specified voltage at 50-60 Hz continuously nected together, should then be tested by applying
for one minute. a voltage between the circuit and the grounded
DC high-potential testing should be performed (earthed) frame or core , equal to 1500 volts AC (2600
by applying specified voltage for a duration of one volts DC). During each device circuit test, all other
minute after test voltage is reached. The DC potential machine windings and components should be con-
should be increased gradually in steps or ramps to nected together and to the grounded (earthed) frame
the desired test voltage in order to limit the charg- or core. (Reference: NEMA Stds. MG 1, 3.1.8.)
ing current.
Caution: After completion of a DC high-potential 4.4.2.2 Accessories of Machines with
test, ground (earth) the winding to the frame (or core) Reconditioned Windings
until the charge has decayed to zero. (References: The high-potential test for accessory circuits of
IEEE Stds. 4 and 95; and NEMA Stds. MG 1, 3.1.1.) reconditioned machines should be performed at 65%
of the new device test value.
4.4.1 Windings
4.4.2.3 Accessories of Machines with
4.4.1.1 New Windings
Windings Not Reconditioned
High-potential tests should be applied as specified
Accessory circuits of machines which have not
in Table 4-4 for AC voltage and Table 4-5 for DC volt-
age. To avoid excessive stressing of the insulation, had their windings reconditioned should have an
repeated application of the high-potential test volt- insulation resistance test with a 500v megohmmeter.
age is not recommended. Immediately after rewind, Insulation resistance should be 1 megohm or greater.
when a high-potential test of the winding is required, 4.5 NO-LOAD TESTS
it is recommended that the test voltage not exceed After a motor has been assembled it should be
80% of the original test voltage. The tests should be run under no load conditions to ensure it operates
applied once only at the specified voltage.
satisfactorily. To prepare for this, the motor should
4.4.1.2 Reconditioned Windings be securely mounted on a base plate or resilient pad
High-potential tests for reconditioned windings if and energized. A secured half-key should be fitted
approved by the customer should be performed at in the keyseat (keyway).
65% of the new winding test value.
Caution: If the weight of a rotating element is not
4.4.1.3 Windings Not Reconditioned sufficient to provide the minimum preload for a bear-
Machines with windings not reconditioned should ing, an artificial load should be used to provide the
have an insulation resistance test instead of a high- required bearing preload.
potential test.
4.5.1 Speed
4.4.2 Accessories For AC motors, no-load running tests should be
4.4.2.1 New Accessories made at rated voltage and rated frequency. The speed
Accessories such as surge capacitors, lightning ar- should be measured and compared with nameplate
resters, current transformers, etc., which have leads speed.
connected to the machine terminals should be dis- For VFD-powered AC motors that run above base
connected during the test, with the leads connected speed, additional testing should be done at maximum
together and to the grounded (earthed) frame or rated motor frequency.
core. These accessories should have been subjected Shunt-wound and compound-wound DC motors
to the high-potential test applicable to the class of should be run with rated voltage applied to the
machine at their point of manufacture. Capacitors of armature, and rated current applied to the shunt
capacitor-type motors must be left connected to the field. The speed should be measured and compared

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