Class 2 and Class 3 Transformers

The products listed here are transformers, herein called Class 2 or Class 3 transformers, for use with Class 2 or Class 3 circuits, respectively, in accordance with the National Electrical Code, ANSI/NFPA 70. They are intended for connection to essentially sinusoidal supply sources. Permanently connected transformers are rated 600 volts or less, and cord and plug connected transformers are rated 120 volts or less.

A Class 2 or Class 3 transformer that is inherently limited has an impedance within the transformer that limits the current output to a particular maximum value. It may or may not be provided with a thermostat or other temperature sensitive device to limit its maximum temperature.

A Class 2 or Class 3 transformer that is not inherently limited does not have an impedance to limit the maximum current output to a specified value. However, the maximum power output is limited by an overcurrent-protective device.

A Class 2 or Class 3 transformer that includes a separate current-limiting impedance, such as a resistor or a positive temperature coefficient device (PTC), is covered by these requirements.

A Class 2 transformer has a 30-volt rms maximum secondary potential under any condition of loading or open circuit.

A Class 2 or Class 3 transformer that includes a resonance regulating circuit is covered by these requirements.

These requirements do not cover power supplies, toy transformers, direct plug-in transformers, or transformers intended for use in audio-, radio-, or television-type appliances. A transformer provided with a rectifier is considered to be a power supply.

The requirements in this standard may be modified by requirements in an end product standard if a transformer is intended for use only as a component in other equipment.These products comply with ARL requirements which include pertinent sections of the following standard: ANSI/UL 1585, “Class 2 and Class 3 Transformers.”

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.

Only products which properly bear the ARL Listing Mark (Label) are considered Listed by ARL.