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An electronic phase-sequence indicator for indicating the cyclic sequence order for three-phase electric systems using a single-phase indicator-detector having an ammeter circuit and a voltmeter circuit interconnected to the three-phase system with resistors and capacitors, or alternatively with inductances and capacitors.
The voltmeter moving element is placed between the pole pieces of a ferromagnetic circuit and is composed of a small freely rotatable frame, upon which the voltmeter small coil is wound and which is composed of many turns of a very thin copper wire. Upon the axle of the small frame two spiral springs are mounted having the functions of determining the counteracting torque and of conveying the voltmeter current to the small coil.
The voltmeter pointer is mounted upon the axle of the voltmeter moving element and is of the center-zero type, with a dial, divided by a line into two sectors, each of which respectively represents a predetermined indication for the correct and simple use of the sequence-phase indicator.
Fig(Phase Sequence Indicator)