Foster Transformer Company

Class 2 Transformers

Class 2 Transformers

Class 2 Transformers and SELV Low Voltage Control Transformers.

Class 2 or Class II control transformers represent one of the most common commercial transformer applications, and are found in a broad range of industrial, medical, and consumer applications. Class 2 transformers have unique characteristics to enhance safety. Most notably, low secondary voltage to reduce electrical shock hazard and low power to reduce fire hazard. The specific design requirements for Class 2 and Class 3 transformers are described in Underwriters Laboratories Standard UL 5085-1 and UL 5085-3 (formerly UL 1585) and CSA C22.2 No. 66.1 and C22.2 No. 66.3 (formerly CSA C22.2 No. 66). Class 2 circuits themselves are defined in the National Electrical Code, NFPA 70, Article 725. While there is no direct equivalent to Class 2 circuits abroad, EN 61558-1 (Safety of Power Transformers) and EN 61558-2-6 (Particular Requirements for Safety Isolating Transformers for General Use) have an analogue, Safety Isolating Transformers, which provide power to SELV (safety-extra-low-voltage) circuits.