Simplified circuit diagram of a <a href="https://en.wikipedia.org/wiki/quadrature_booster" class="extiw" title="en:quadrature booster">quadrature booster</a>, or phase-shifting transformer.<br>
The quadrature booster consists of two <a href="https://en.wikipedia.org/wiki/transformer" class="extiw" title="en:transformer">transformers</a>, a shunt unit and a series unit. Each phase of the shunt unit's primary winding is connected across a pair of the incoming lines and so is 90° in phase behind the other line, that is, it is at <a href="https://en.wikipedia.org/wiki/quadrature" class="extiw" title="en:quadrature">quadrature</a>. Its secondary is connected to the primary of the series unit, whose secondary winding is in series with the other line. The resulting voltage is thus the <a href="https://en.wikipedia.org/wiki/vector_sum" class="extiw" title="en:vector sum">vector sum</a> of the incoming voltage and the quadrature component.
<a href="https://en.wikipedia.org/wiki/User:BillC" class="extiw" title="en:User:BillC">BillC</a>
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