Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

overvoltage relay
a protective relay that operates on overvoltage.
photovoltaic
effect a photoelectric phenomenon in certain photorefractive crystals, for example, LiNbO3, BaTiO3, LiTaO3,in which the illumination of light leads to the generation of electric current along certain direction in the crystals. This leads to the accumulation of charges on the surfaces of the crystals, causing an open circuit voltage.
photovoltaics
conversion of insolation into DC electricity by means of solid state p-n junction diodes.
pickup voltage

See pickup current
primary voltage
in power distribution the voltage at the primary winding of the distribution transformer.
rated voltage
the voltage at which a power line or electrical equipment is designed to operate.
reduced-voltage motor starter
a device designed to safely connect an electric motor to the power source while limiting the magnitude of its starting current. Various electromechanical configurations may be used: primary resistor, delta-wye, part-winding (requires special motor or dual voltage windings). Power electronic devices may also be utilized to gradually increase the applied voltage to system levels. The complete starter must also include fault and overload protection.
sealing voltage
the voltage necessary to complete the movement of the armature of a magnetic circuit closing device from the position at which the contacts first touch each other.
secondary voltage
in power distribution work the voltage at the secondary of the distribution transformer.
secondary voltage control
an automatic voltage control scheme that is similar in function to the automatic voltage regulator, but its purpose is to control a bus voltage which need not have a synchronous generator connected at the bus.
step voltage
in power system safety studies, the voltage measured across two points on the ground which are separated by a distance equal to an average person's step while walking over the area in question.
surge response voltage
the voltage that appears at the output terminals of surge protection equipment and is seen by loads connected to that device both during and after a surge condition.
undervoltage
a voltage that is less than nominal for a time greater than 1 minute.
undervoltage relay
a protective relay that operates on low voltage or loss of voltage.
utilization voltage
the voltage across the power input terminals of a piece of electrical equipment.
voltage collapse
the rapid and uncontrollable drop of bus voltage due to a slight increase in load at the bus, generally characterized by inadequate reactive support in a high-load area.
voltage variation
long duration a change of voltage RMS value from nominal for a time period greater than 1 minute, and can be used with the words showing a magnitude change such as overvoltage, or under-voltage.
Volta
Volta, Alessando (Corte) (1745-1827) Born: Como, Italy

is best known for the invention of a number of practical devices including the first battery (voltaic pile), a simple electrometer for measuring current and electrophorus. Volta was not a theoretical physicist, but a good researcher. He was able to follow up Benjamin Franklin's early work and that of Luigi Galvani by devising devices and experiments that allowed him to explore the physics. Volta is honored by having his name used as the unit of electromotive force, the volt.
voltage
the potential to do work, voltage is the ratio of the energy available to the charge, expressed in volts.
voltage coefficient of resistance
the change in resistance per unit change in voltage, expressed as a percentage of the resistance at 10% of rated voltage.
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