Interphase unbalance detector for AC load circuit

Abstract

In polyphase AC load circuits, the current of each phase, which varies over a wide range, is led out to detect the unbalances of currents in the respective phases at arbitrarily adjustable predetermined unbalance factor by stationary-type device. The DC voltages (E.sub.U to E.sub.W) corresponding to the currents in the respective phases are divided into forward constant-voltage elements (D.sub.1 to D.sub.3) and passive voltage varying elements (VR.sub.1 to VR.sub.3). The voltages at the elements (VR.sub.1 to VR.sub.3) are defined as current comparison voltages (e.sub.1 to e.sub.3), and the voltages (E.sub.U to E.sub.W) in the respective phases are reduced by level adjusting circuits (LA.sub.1 to LA.sub.3) to reference level voltages (e.sub.U to e.sub.W). Both voltages (e.sub.U to e.sub.W) and (e.sub.1 to e.sub.3) are applied to the positive and negative terminals of the same elements (D.sub.4 to D.sub.6) to thus form an unbalance detecting circuit. When an unbalance occurs between two phases of the load circuit to cause the voltages (e.sub.1 to e.sub.3) to be lower than the voltages (e.sub.U to e.sub.W) over the constant voltage of the elements (D.sub.4 to D.sub.6), relays (RY.sub.1 to RY.sub.3) are operated to break the circuit or to generate an alarm. The unbalance factor detecting sensitivity of this device is determined by the setting factor of the reference level voltages (e.sub.U to e.sub.W) adjusted by the variable resistors (R.sub.1 to R.sub.3) in the adjusting circuits (LA.sub.1 to LA.sub.3).

Dependencies are inferred from the claim text.