Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

integral horsepower motor
a motor built in a frame as large as or larger than that of a motor of open construction having a continuous rating of one horsepower at 1700-1800 rpm.
interharmonic component
the frequency component that is not an integer value of the periodic supply waveform.
interior permanent magnet machine
a permanent magnet machine in which the permanent magnets are buried in the rotor iron. With this construction the airgap is small, allowing the airgap flux to be reduced by current control. This allows an operating mode in which the top speed of the motor can be as much as five times the base speed, and is one of the main features of this motor.
interruptible load
a load, typically of a commercial customer, which by contract may be interrupted by the utility for purposes of system stability.
interrupting capacity

See interrupting rating
interrupting rating
for a circuit breaker, fuse, or switch, the maximum fault level that the device can safely interrupt. The interrupting rating can be expressed in terms of amps or volt-amps.
intrinsic impedance
(1) the impedance presented when a source is open-circuited.

(2) a characteristic parameter associated with a medium that is the ratio of the magnitudes of the transverse components of the electric field intensity and magnetic field intensity for a wave propagating in a given direction. It has units of ohms.
jumper
a plug or wire used for setting the configuration of system. It can be used for changing the hardware configuration by forcing some line to be high or low. It is used to change software configuration (especially on embedded systems) when the status of the jumper is read by the microprocessor.
jumping jack
a voltmeter.
kilovolt-ampere (KVA)
a measure of apparent power, often in the rating of a piece of equipment or the measure of an electrical load, which is obtained by multiplying the device voltage in kilovolts by the current in amperes.
klydonograph
a measuring instruments for high-voltage impulses which makes use of Lichtenburg figures impressed on photographic film.
left-hand circular polarization
the state of an electromagnetic wave in which the electric field vector rotates anticlockwise when viewed in the direction of propagation of the wave.
line drop compensator
a multiply-tapped autotransformer equipped with a load-sensing relay which will adjust the line voltage to compensate for the impedance drop in the circuit between the device and the load center.
line impedance stabilization network (LISN)
a network designed to present a defined impedance at high frequency to a device under test, to filter any existing noise on the power mains, and to provide a 50 Ω impedance to the noise receiver.
load tap changer (LTC)
a tapped transformer winding combined with mechanically or electronically switched taps that can be changed under load conditions. The load tap changer is used to automatically regulate the output of a transformer secondary as load and source conditions vary.
load-pull
the systematic variance of the magnitude and phase of the load termination of a device under test.
low-pressure discharge
a discharge in which the pressure is less than a torr or a few torrs; low-pressure gases can be easily excited, giving spectra characteristic of their energy structure.
magnetic clamp
a device employing a magnetic field to deliver a clamping action.
magnetic damper
any device using a magnetic field to damp motion.
magnetic dipole
an arrangement of one or more magnets to form a magnet system that produces a magnetic field with one pair of opposite poles.
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