Shunting

(electricity) The act of connecting one device to the terminals of another so that the current is divided between the two devices in proportion to their respective admittances.

The act of connecting an electrical element in parallel with (across) another element. The shunting connection is shown in illus. a.

resistor R_S.">
Shunting. (a) Shunting connection. (b) Ammeter shunted by resistor R_S.

An example of shunting involves a measuring instrument whose movement coil is designed to carry only a small current for a full-scale deflection of the meter. To protect this coil from an excessive current that would destroy it when measuring currents that exceed its rating, a shunt resistor carries the excess current.

Illustration b shows an ammeter (a current-measuring instrument) with internal resistance R_A. It is shunted by a resistor R_S. The current through the movement coil is a fraction of the measured current, and is given by the equation below. With different choices of R_S, the measuring range for the current I can be changed. See also Ammeter; Current measurement.

Similar connections and calculations are used in a shunt ohmmeter to measure electrical resistance. Shunt capacitors are often used for voltage correction in power transmission lines. A shunt capacitor may be used for the correction of the power factor of a load. In direct current shunt motors, the excitation (field) winding is connected in parallel with the armature. See also Direct-current motor; Ohmmeter; Power factor; Resistance measurement.

In electronic applications, a shunt regulator is used to divert an excessive current around a particular circuit. In broadband electronic amplifiers, several techniques may be used to extend the bandwidth. For high-frequency extension, a shunt compensation is used where, typically, a capacitor is shunted across an appropriate part of the circuit. Shunt capacitors (or more complicated circuits) are often used to stabilize and prevent undesired oscillations in amplifier and feedback circuits. See also Amplifier; Feedback circuit.

The diversion of blood from one region of the body to another. During exercise, special vessels, called shunt vessels, enable blood to be diverted from the intestines to skeletal muscle.

Shunting

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)