Page 20 - EASA_AR100-2015_0815 APEX_IESCO

Section 4, Page 3 EASA AR100-2015 Recommended Practice - Rev. August 2015

if a DC voltage is used. ples, thermistors, resistance temperature detectors,
AC high-potential testing should be performed by etc.), connected other than in the line circuit, should
applying specified voltage at 50-60 Hz continuously be connected to the grounded (earthed) frame or
for one minute. core during machine winding high-potential tests.
DC high-potential testing should be performed Each of these component device circuits, with leads
by applying specified voltage for a duration of one connected together, should then be tested by apply-
minute after test voltage is reached. The DC poten- ing a voltage between the circuit and the grounded
tial should be increased gradually to the desired (earthed) frame or core. The high-potential tests
test voltage in order to limit the charging current. should be applied as specified in Table 4-3 for AC
Caution: After completion of a DC high-potential voltage and Table 4-4 for DC voltage. During each
test, ground (earth) the winding to the frame (or device circuit test, all other machine windings and
core) until the charge has decayed to zero. (Refer- components should be connected together and to the
ences: IEEE Stds. 4 and 95; and NEMA Stds. MG 1, grounded (earthed) frame or core. (Reference: NEMA
3.1.1.) Stds. MG 1, 3.1.8.)

4.4.1 Windings
4.4.2.2 Accessories of Machines with
4.4.1.1 New Windings Reconditioned Windings
High-potential tests should be applied as specified The high-potential test for accessory circuits of
in Table 4-1 for AC voltage and Table 4-2 for DC reconditioned machines should be performed at 65%
voltage. To avoid excessive stressing of the insula- of the new device test value.
tion, repeated application of the high-potential test
voltage is not recommended. Immediately after 4.4.2.3 Accessories of Machines with
rewind, when equipment is installed or assembled Windings Not Reconditioned
and a high-potential test of the entire assembly is Accessory circuits of machines which have not
required, it is recommended that the test voltage had their windings reconditioned should have an
not exceed 80% of the original test voltage. The tests insulation resistance test with a 500v megohmmeter.
should be applied once only at the specified voltage. Insulation resistance should be 1 megohm or greater.
(Reference: NEMA Stds. MG 1, 12.3.) 4.5 NO-LOAD TESTS
4.4.1.2 Reconditioned Windings After a motor has been assembled it should be
High-potential tests for reconditioned windings run under no load conditions to ensure it operates
should be performed at 65% of the new winding satisfactorily. To prepare for this, the motor should
test value. be securely mounted on a base plate or resilient pad
and energized. A secured half-key should be fitted
4.4.1.3 Windings Not Reconditioned
Machines with windings not reconditioned should in the keyseat (keyway).
have an insulation resistance test instead of a high- 4.5.1 Speed
potential test. For AC motors, no-load running tests should be
made at rated voltage and rated frequency. The
4.4.2 Accessories
speed should be measured and compared with
4.4.2.1 New Accessories nameplate speed.
Accessories such as surge capacitors, lightning For VFD-powered AC motors that run above base
arresters, current transformers, etc., which have speed, additional testing should be done at maxi-
leads connected to the machine terminals should mum rated motor frequency.
be disconnected during the test, with the leads con- Shunt-wound and compound-wound DC motors
nected together and to the grounded (earthed) frame should be run with rated voltage applied to the
or core. These accessories should have been subjected armature, and rated current applied to the shunt
to the high-potential test applicable to the class of field. The speed should be measured and compared
machine at their point of manufacture. Capacitors of with nameplate base speed and should be within 1%
capacitor-type motors must be left connected to the for both directions. If the motor is rated for speeds
winding in the normal manner for machine opera- above base speed, field power should be varied to
tion (running or starting). achieve maximum rated speed. Note field current
Component devices and their circuits, such as at maximum speed.
space heaters and temperature sensing devices in Series-wound motors should be separately excited
contact with the winding (thermostats, thermocou- when tested due to danger of runaway.

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