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47.10.11 For a transformer that is provided with a protective device built into the transformer or that is
being tested in conjunction with an external protective device, a test described in 47.10.1 (a) – (c) is to be
discontinued if the protective device opens the circuit and the next test in the sequence is to be started.
This procedure is to be continued until a condition specified in 47.10.1 (a) – (c) is reached that allows the
circuit to hold for 15 days. The protective device mentioned above includes automatic recycling type,
manual reset type, or a replaceable type.
47.10.11 effective April 13, 1993
47.10.12 If a protective device opens the circuit or a winding on any sample opens during the 15-day
abnormal operation tests while the samples are unattended, the variable resistor load on the other
samples is to be increased, by reducing the resistance, until the protective device opens the circuit or the
winding opens, so that the samples may be subjected to the dielectric voltage withstand test described in
47.10.3 while in a heated condition. The next test in the sequence is to be in accordance with 39.1 (b)
and (c).
47.10.12 effective April 13, 1993
47.10.13 Samples for the 15-day abnormal operation tests described in 47.10.1 are to be prepared as
follows:
a) The transformer is to be mounted either in the converter or inverter enclosure as intended or
on a test bench with a double layer of cheesecloth draped over the transformer.
b) All secondary windings are to be loaded to rated current before the abnormal condition is
introduced; and the loads, other than that connected to the winding to be overloaded, are not to
be readjusted thereafter.
47.10.13 effective April 13, 1993
47.11 Blocked fan
47.11.1 A converter or inverter having a fan motor shall be operated for 7 hours with the rotor of the fan
motor stalled from rotating.
47.11.1 effective April 13, 1993
48 Evaluation of Reduced Spacings on Printed Wiring Boards
Section 48 effective April 13, 1993
48.1 General
48.1.1 In accordance with Exception No. 4 to 28.1.1, printed wiring board traces of different potential
having reduced spacings may be investigated by conducting a dielectric voltage-withstand test as
described in 48.2.1 and 48.2.2 for a protected environment, see 7.1 – 7.5, or a shorted trace test as
described in 48.3.1 and 48.3.2 for a converter or inverter investigated for either a protected environment
or a general environment.
48.2 Dielectric voltage-withstand test
48.2.1 A printed wiring board as mentioned in 48.1.1 shall withstand for 1 minute without breakdown the
application of a dielectric withstand potential applied between the traces having reduced spacings in
accordance with 39.1 and 39.2.
DECEMBER 14, 1993UL 45866
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