Current Sense Transformer
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Current sense transformers, also called current sensing transformers or current transformers, are static electrical devices used to measure alternating electric currents (AC). When the current in a circuit is too high to directly apply to measuring instruments, a current sense transformer will reduce the current to an accurate proportion that can be conveniently connected to recording or measuring instruments. Current sensing transformers can also isolate instruments from potentially very high voltage in monitored circuits. Current transformers are most commonly used for measuring current in a power grid, and monitoring its operation. These devices, in conjunction with voltage leads, drive watt-hour meters on virtually every building with three-phase electrical service, as well as those with single-phase electrical service greater than 200 amps. Multiple current sense transformers may be stacked for isolation between metering and protection circuits, among other functions. A current transformer consists of a primary winding, a magnetic core, and a secondary winding. The most common design involves a length of wire wrapped many times around a silicon steel ring, which is, in turn, passed around the circuit being measured. Shapes and sizes can vary greatly. Current sensing transformers are generally described by their current ratios (primary/secondary).