Improved arrangement for alternating current relays

Abstract

Abstract 370,899. Protective cut-out arrangements and electromagnetic relays. STAGE, S. J., Malm÷, Sweden. Jan. 6, 1931, No. 458. Convention date, Jan. 7, 1930. [Class 38 (v).] Relays such as impedance and reverse current relays having a voltage and a currentresponsive element are arranged with a series resonant circuit connected in series with the voltage-responsive element, this circuit having a natural frequency substantially equal to that of the line to which the relay is connected so that during response to short-circuit conditions, which are accompanied by an excessive drop in line voltage the action of the resonant circuit causes a persistence of current in the voltage coil for a time sufficient to ensure the operation of the relay. As shown in the Figure, the voltage coil 3 fed from the voltage transformer 2 has in series an inductance 5 and condenser 6. Additionally an ohmic resistance 4 is included in the series circuit which is of the same order of magnitude as the wave resistance, i.e. the square root of the ratio of inductance to capacity of the circuit. Normally the effects of the inductance and capacity neutralize each other the current being determined by the ohmic resistance, the major portion of which consists of the resistance 4, but on a sudden collapse of the voltage across the line 1 the effect of the inductance and capacity cause an appreciable current to persist in the voltage coil circuit for some cycles, this current having an amplitude sufficiently great to ensure the operation of the relay. In modified arrangements, Figs. 3 and 4 (not shown), the resistance 4 may be connected across an inductance 5 and condenser 6, and an additional inductance or condenser may be connected in series with the main voltage coil circuit. The currentresponsive element 7 of the relay is fed directly from a current transformer 8 in the line 1.

Inventors

No inventors recorded.

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