UL Standard for Safety Transformers and Motor Transformers for Use in Audio-@ Radio-@ and Television-Type Appliances (Sixth Edition; Reprint with revisions through and including June 16@ 2011)
These requirements apply to transformers@ autotransformers@ and motor-transformers intended to be used in audio-@ radio-@ and television-type appliances in which the primary winding is connected across the supply circuit. The requirements in Sections 4 ?C 15@ 23 ?C 26@ 28@ and 29 also apply to transformers intended for use in high-frequency@ switching-type power supplies in which the transformer provides isolation from the supply circuit. These requirements do not apply to transformers that are intended to transform only audio@ video@ and other signal waveforms. Those transformers are covered by the Standard for Isolating Signal and Feedback Transformers for Use in Electronic Equipment@ UL 1876. These requirements apply to a transformer or motor transformer that includes a separate current-limiting impedance such as a positive temperature coefficient (PTC) device complying with the requirements for thermistor-type devices@ or a resistor complying with the Standard for Fusing Resistors and Temperature-Limited Resistors for Radio- and Television-Type Appliances@ UL 1412. A product that contains features@ characteristics@ components@ materials@ or systems new or different from those covered by the requirements in this standard@ and that involves a risk of fire or of electric shock or injury to persons shall be evaluated using appropriate additional component and end-product requirements to maintain the level of safety as originally anticipated by the intent of this standard. A product whose features@ characteristics@ components@ materials@ or systems conflict with specific requirements or provisions of this standard does not comply with this standard. Revision of requirements shall be proposed and adopted in conformance with the methods employed for development@ revision@ and implementation of this standard.