Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

half-power point
The two-sided half-power bandwidth is twice the half-power point.
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.
half-wave voltage
the voltage required to produce an amount of refractive index change in a medium that will retard the phase of a traversing optical wave.
harmonic analysis
the branch of mathematics dealing with the decomposition of signal functions as a linear combination of basis functions which represent "waves" of various frequencies.

When the basis functions are sines and cosines each with a frequency that is an integer multiple of the signal's frequency, we have trigonometric harmonic analysis, in other words classical Fourier analysis, which provides the amplitudes and phases of the constituent sinusoids.
harmonic component
a Fourier component of order greater than one of a periodic waveform.
harmonic content
the internally generated, harmonically related spectral output from a device or circuit. Harmonic energy is that energy that is at exact multiples of the fundamental frequency, generated by the nonlinearities within the device or circuit acting on the fundamental frequency.
harmonic distortion
caused by the nonlinear transfer characteristics of a device or circuit. When a sinusoidal signal of a single frequency (the fundamental frequency) is applied at the input of a nonlinear circuit, the output contains frequency components that are integer multiples of the fundamental frequency (harmonics). The resulting distortion is called harmonic distortion.
harmonic frequency
integral multiples of fundamental frequency. For example, for a 60-Hz supply, the harmonic frequencies are 120, 180, 240, 300, ....
harmonic load-pull measurement
a measurement method where transfer characteristics of a device at the fundamental
frequency can be measured by electrically changing the load impedance at harmonic frequencies.
harmonic sinusoidal
component of a periodic waveform that has a frequency equal to an integer multiple of the basic frequency (or fundamental frequency). Thus the third harmonic of a power system voltage in the U.S. has a frequency of 3 x 60, or 180 Hz. For electric systems powered by sinusoidal sources, harmonics are introduced by nonlinear devices such as saturated iron cores and power electronic devices.
heat sink
aluminum mountings of various shapes and sizes used for cooling power semiconductor devices. Heat sinks can be cooled by either natural convection or a fan, and heat dissipation can be improved by a coating of black oxide or if the heat sink is made with fins.
See overload heater
hermetic seal
a seal that is such that the object is gas-tight (usually a rate of less than 1 × 10-6 cc/s of helium).
a unit of frequency.
high pass filter
filter exhibiting frequency selective characteristic that allows high-frequency components of an input signal to pass from filter input to output unattenuated; all lower frequency components are attenuated.
high phase order (HPO)
polyphase systems that contain 6, 9, or more phases — rather than the standard three-phase system.

HPO systems may be used to provide a means of transmitting more electrical power down existing right-of-ways than three-phase systems, without an increase in transmission voltage, and without an increase in EMF levels at the edge of the right-of-way.
high rupturing capacity (HRC)
a term used to denote fuses having a high interrupting rating. Most low-voltage HRC-type fuses have an interrupting rating of 200 kA RMS symmetrical.
high side
pertains to the portion of a circuit connected to the higher voltage winding of a power transformer.
high-loss resonator
a resonator having a high value of loss (usually diffraction loss) per round trip; unstable resonator.
high-pass filter
a filter that has a transfer function, or frequency response, whose values are small for frequencies lower than some intermediate frequency. A filter whose impulse response is a high-pass signal.