UL 506:2008 pdf download – Specialty Transformers.
33 Open-CircuIt Secondary Operation Test
33.1 A specialty step-up transformer is to be operated continuously for 24 hours at maximum rated primary voltage and rated frequency. with the secondary open-circuited. There shall not be malfunction of the insulation.
34 Switch Tests
34.1 General
34.1.1 A switch provided with a specialty step-up transformer is to be sublected to the overload and endurance tests described in 34.2.1 — 34.3.2.
Exception: A switch having a current rating not less than twice that of the transformer primary and a voltage rating not less than that of the transformer pnmavy need not be subjected to the tests.
34.2 Overload
34.2.1 Three samples of each switch are to be subjected to an overload test consisting of 50 cycles of operation at 10-second intervals, opening and closing the primary circuit of the transformer. During the test, the transformer primary is to be connected to a supply Circuit f maximum rated primary voltage and rated frequency and the secondary terminals are to be short-circuited. There shall not be undue burning or pitting of the contacts or other damage.
34.2.2 The switches are to be mounted in the transformer enclosure in the intended manner during me test, and the enclosure is to be grounded through a 15-ampere fuse that would not open as a result of the test.
34.3 Endurance
34.3,1 After the overload test, the same three samples of each switch are to be subjected to an endurance test consisting of 1000 cycles of operation at 1-second intervals with the primary of the transformer connected to a supply circuit of maximum rated primary voltage and rated frequency. The secondary of the transformer is to be connected to a load of such magnitude as to result in an input of rated primary current: or the secondary terminals are to be short-circuited. The switches are to be tested under the conditions described In 34.2.2 with the same criteria for acceptance.
34.3.2 Snap switches and other wiring devices are to be disconnected during the Dielectric Voltage-Withstand Test, Section 31, and are to be subjected to a separate dielectric voltage-withstand test. A wiring device is to be subjected for 1 minute to the applicabon of an essentially sinusoidal potential of 1000 volts between all kve and dead metal parts. There shall be no cefectric breakdown.
37 Details
37.1 A transformer shaH have a plain, legible marking that Is readily visible after the transformer has been installed as intended with the following:
a) The manufacturer’s name, trademark, or other descriptive marking by which the organization responsible fo the product can be identified;
b) The catalog number or the equivalent;
c) The electrical rating; and
d) The date of manufacture which may be abbreviated or in an established or otherwise
traceable code or a code affirmed by the manufacturer, that will enable the transformer to be
identified as being manufactured within a three-month period.
If any point of the secondary winding is grounded, the marking shall indicate specifically which point is grounded.
37.2 A weatherproof transformer shall be marked with the word “Weatherproof” or the designation “WP.
A transformer not investigated for use outdoors, other than an open core-and-coil transformer. and a
transformer provided with a power supply cord shall be marked with the following or equivalent marking:
“For indoor use only
38 Details
38.1 An ignition transformer Is a step-up transformer of the high-secondary-voltage type, intended to
provide ignition for an oil or gas burner.
382 The requirements for ignition transformers specified in 38.3 — 544 shall be considered in addition to
those specified in Sections 1 — 17.
383 An interchangeable ignition transformer, identified as a Class 6, 10, 12, or 14 transformer, is electrically interchangeable with any other transformer of the same class and having a similar form of secondary grounding on gas- or oil-burning equipnient that has been investigated and determined to be acceptable. Noninlerchangeable ignition transformers may be used only on oil or gas burners with which they have been tested. A Class 6 interchangeable transformer is one having a secondary voltage rating of 6000 volts: the corresponding ratings for Class 10. 12, and 14 transformers are 10.000, 12,000. and 14.000 volts, respectively. A transformer having a secondary voltage rating of 15,000 volts may be tested as a Class 14 transformer.