PROTECTION SYSTEM FOR AC GENERATORS

• Main Authors: GRAVEREAUX; DANIEL W, DEROSA, JR.; JOSEPH J, BODENHEIMER; BERT A
• Format: Patent
• Language: English
• Published: 27.04.1993
• Subjects: BLASTING; COMBUSTION ENGINES; COMBUSTION ENGINES IN GENERAL; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS; GENERATION; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; INTERNAL-COMBUSTION PISTON ENGINES; LIGHTING; MECHANICAL ENGINEERING; WEAPONS

A circuit for protecting the ac generator and/or load of a diesel-engine generator set is provided. Included is a circuit for measuring indications of the current in each phase of the ac generator, and a switching circuit for protecting the ac generator if the current in any phase is greater than a predetermined current for a predetermined length of time, or if the current in any phase is less than a predetermined function of the currents in each of the phases for the predetermined length of time. For diesel-engine generator sets which generate three phase 460 V at up to thirty amperes continuously, the preferred predetermined overcurrent for any phase of the ac generator is thirty-five amperes, and the predetermined length of time (to permit inrush currents) is five seconds. Preferably the current in any phase should be less than fifty percent of the average of the current in the three phases. The circuit which protects the ac generator preferably short circuits the field winding of the ac generator and thereby turns off the ac generator, and/or closes a fuel valve to effectively turn off the engine should the current imbalance or overcurrent be sensed for the five seconds. In conjunction with the protection circuit, a switch interlock and/or circuit breaker arrangement for shock protection is provided to short circuit the field winding upon the (dis)connection of the generator to the load by plug insertion/removal into a socket of the ac generator.