Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

fractional horsepower
National Electrical Manufacturers Association (NEMA) classification describing any "motor built in a frame smaller than that having a continuous rating of 1 horsepower, open type, at 1700 to 1800 rpm."
full-wave rectifier
a device that passes positive polarity portions of a signal and reverses negative polarity portions of an AC signal. Ideally, for a sinusoidal input vi(t) = Vm cos(ωt), the output of an ideal full-wave rectifier is vo(t) = |Vm cos(ωt)|.
fused disconnect
a disconnect switch that also employs fuse(s) for the purpose of over-current protection.
half-wave rectifier
a device that passes positive polarity portions of a signal and blocks negative polarity portions of an AC signal. Ideally, for a sinusoidal input vi.t) = Vm cos.!t/, the output equals the input while the input is positive and is zero while the input is negative.
holographic interconnect
free-space interconnect that uses holograms to control optical paths from sources to detectors. The hologram provides the interconnection by forming the intentionally distorted image of the source array on the detector array. A hologram can be viewed as a combination of gratings. Each grating directs a light beam passing through it to a new direction. The hologram can be displayed by a spatial light modulator to achieve dynamic reconfiguration.
hydroelectric generator
large, three-phase synchronous alternator powered by a water-driven turbine. See also generator.
inductance
a parameter that describes the ability of a device to store magnetic flux. The units are henrys per meter.
induction furnace
a method of smelting or heating metals with eddy currents induced by a high-frequency coil surrounding the crucible.
induction generator
an induction machine operated as a generator. If the machine is connected to an AC system and is driven at greater than synchronous speed, the machine can convert mechanical energy to electrical form. The induction generator requires a source of reactive power.
induction machine
classification of any of a variety of electrical machines in which an AC current in the stator coils is used to produce a rotating magnetic flux that, by Faraday action, induces an AC voltage in a set of coils (the induction coils) on the machine's rotor. The rotor coils are shorted to cause a second AC current to flow in the rotor coils, which produces, in turn, a second rotating flux. The interaction of the rotor-and stator-produced fluxes creates torque.
induction motor

See induction machine
induction regulator

See induction voltage transformer
induction theorem
states that if the incident tangential magnetic and electric fields are known everywhere on some closed surface, then these fields may be replaced with equivalent electric and magnetic surface currents.
induction voltage transformer
specially constructed transformer with a rotating primary coil that is used to provide voltage regulation on individual power circuits. The secondary of an induction regulator is mounted on the stationary shell of cylindrical core, and the primary is mounted on a movable, center rotor. In the neutral position, the magnetic axes of the primary and secondary coils are oriented 90 degrees to each other, reducing the magnetic coupling to zero. In this position, energizing the primary does not induce voltage in the secondary; however, rotating the primary coil in either direction from the neutral position creates mutual flux linkage and causes a secondary voltage to appear.

Rotation in one direction causes secondary voltage to be in phase with the primary; rotation in the opposite direction causes secondary voltage to be out of phase with the primary. Voltage regulation is provided by connecting the primary coil across the line to be regulated and connecting the secondary coil in series with the load. By positioning the primary coil based on load demand in the line, secondary voltage can be used to adjust line voltage either up or down. Induction regulators are also equipped with a short-circuited coil mounted on the primary in spatial quadrature with the primary coil. In the neutral position, this coil has maximum coupling with the secondary coil, which minimizes the inductive reactance in the load line due to the secondary coil.
inductive coupling
a means of transferring electrical energy from one part (area) of a circuit to another part without requiring any ohmic (wire) connection. Instead, magnetic flux linkages couple two inductors (coils). The coils must be in close proximity in order to establish sufficient mutual inductance.
inductive discontinuity
a type of discontinuity that exhibits an inductive, or quasi-inductive, behavior. As an example, magnetic plane iris in metallic rectangular waveguides produces this type of response.
inductor
a two-terminal electrical element that satisfies a prescribed algebraic relationship in the flux-current (θ - I) plane.
instantaneous contact
the contacts of a contactor or relay that open or close with no time delay.
Institute of Electrical and Electronics Engineers (IEEE)
a professional organization of electrical engineers and computer scientists. The world's largest professional organization.
intrinsic induction
the vector difference between the magnetic induction and the applied external magnetic field, or the magnetic field established by the magnetic material itself.
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