Electricity: electrical systems and devices – Safety and protection of systems and devices – Transformer protection
Patent
1989-05-19
1990-08-21
Deboer, Todd E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Transformer protection
361 37, 361 38, 361104, 361105, 336144, 336219, H02H 704
Patent
active
049511688
ABSTRACT:
A 60 VA transformer is described. A recycling circuit breaker mounted on and connected in series with the secondary winding of the transformer preserves the integrity of the transformer and permits its continued use after a short circuit. A thermal fuse mounted on and connected in series with the primary winding provides short circuit protection in the event the circuit breaker fails in a closed position. Achievement of this end is attained by decoupling the transformer windings to reduce short circuit, secondary current flow. Decoupling is provided by spacing the transformer windings a distance of about 0.090 in. A controlled failure mode provides energy limiting protection for the secondary load circuit in the event of circuit breaker failure in the closed position. Controlled failure is provided by the use of secondary insulation which melts within one minute of a short circuit, permitting turns of the secondary winding to short and reduce current flow to eight amp. within the one minute period. In a second embodiment the thermal fuse and the recycling circuit breaker are both mounted on and connected in series with the primary winding. Shunt plates also increase decoupling of the windings so that short circuit current flow does not exceed eight amp.
REFERENCES:
patent: 2776855 (1942-03-01), Meador
patent: 3532934 (1970-10-01), Ballman
patent: 3611034 (1971-10-01), Astleford, Jr. et al.
patent: 3700965 (1972-10-01), Tone
patent: 4053938 (1977-10-01), Estes
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