Patent GB-191206990-A (GB)
Title: Improvements in Automatic Electric Circuit Breaking Arrangements.
Inventor: MOELLER EGRON OLOF
IPC: H02H3/00
Filed: 1912-03-21
Granted: 1913-03-20
Abstract: 6990. M÷ller, E. O. March 21. Protective arrangements. - In arranging for the automatic opening of electric circuitbreakers under conditions of excessive, minimum, and reverse current, the trip-coil, no-volt-coil, or relay is connected with three resistances of different magnitudes, a low resistance or ' shunt ' in series in one of the mains, and an intermediate resistance and a higher resistance in series with each other across the mains. The trip-coil is connected between the end of the first resistance and the junction of the second and third. Fig. 1 shows the disposition for protecting against maximum and reverse currents, comprising a generator 1, mains 2, 3, circuit-breaker 4, trip-coil 7, low resistance 5, intermediate resistance 6, and high resistance 8. When the potential between the mains 2, 3 is normal, but no current flowing in work-circuit, the current in the trip-coil follows the direction of the arrow and is limited to a low value, insufficient to trip the breaker, by the resistance 8. When forward current flows in the work - circuit and increases sufficiently, the current in the trip-coil falls to zero, and then changes sign, after which it can increase continuously until strong enough to open the circuit-breaker. Upon a reversal in the work circuit, the current in the coil 7 increases with increase in the reverse current until it is sufficient to trip the breaker. To protect against no-volt and reverse current, a no-volt coil is used instead of an overload trip coil, and the positions of the parts 6, 7 are interchanged. The arrangement shown in Fig. 3 for protecting against overload, reverse current, and novoltage is similar to the last described arrangement with the addition of a hot-wire relay 14 adapted to open-circuit the no-volt coil 9. In order to pick up the core of the no-volt coil readily when the circuit-breaker is closed by hand, a winding is provided across part of the resistance 8, additional in effect to the winding 9 during the closing action but afterwards cut out. Fig. 5 shows a tripping-device under the action of three windings, viz., a series winding 17, a shunt winding 19, and a retaining-winding 18. Fig. 6 shows the arrangement modified for alternating current. The low resistance or ' shunt ' 5 is connected across the secondary of a series transformer 25 in the main circuit. The other resistances 26, 28 are connected across the terminals of a potential transformer 29. A hot-wire relay is connected between the end of the ' shunt' 5 and the junction of the other two resistances, and is adapted to close a circuit through a trip-coil 33. The arrangement is designed to operate in case of excessive and reverse current. In a modification of the last arrangement, designed to operate on no-voltage and reversal, the positions of the resistance 26 and the responsive branch 31 are interchanged, the hot-wire relay is normally closed and acts by opening a no-volt coil, and an inductive resistance is used instead of an ordinary resistance 26. The arrangement shown in Fig. 5 may be adapted for alternating current by introducing series and shunt transformers.