Droop current transformer, droop CT or quadrature droop CT - a current transformer used for improvement of regulation of parallel operation of generators.

Typical droop current transformer

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Construction of a droop CT

^{by S. Zurek, E. Magnetica, CC-BY-3.0}

Such current transformers do not have any special construction. They follow the usual design for CTs but are used for special role to facilitate sharing the reactive load in parallel circuits. For this reason their parameters (e.g. operating primary current and rated burden) must be selected for the correct type of generator. Also, the polarity must be connected correctly and on the correct phase (in three-phase systems). ¹⁾

If a generator is to work alone, then the signal from the droop CT can be shorted or the droop compensation disabled, as it does not add any useful information for the control circuit.²⁾

The secondary winding terminals are sometimes referred to as S1 and S2, and the primary as P1 and P2, respectively.³⁾⁴⁾

• Current transformer