Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

Ward-Leonard drive
an adjustable voltage control drive system for the speed control of DC machines, whereby variable voltage is supplied to the armature, while maintaining constant voltage across the shunt or separately excited fields. The variable voltage is obtained from a motor-generator set. The Ward-Leonard drive was frequently used in elevators.
warm start
(1) reassumption, without loss, of some processes of the system from the point of detected fault.

(2) the restart of a computer operating system without going through the power-on (cold) boot process.
water resistivity
a measure of the purity of cooling liquid for a power tube, typically measured in megohms per centimeter.
unit of power in the SI system of units.
Watt, James (1736-1819) Born: Greenock, Scotland, U.K.

is best known for his work in the development of efficient steam power. Watt began his career as an instrument maker.
When asked to fix a troublesome Newcomen engine, he began to make improvements.

Watt eventually partnered with industrialist Matthew Boulton to form a steam engine company. Watt is credited with having devised the horsepower system. The unit of power, the watt, is named in his honor.
watt-VAR meter
meter capable of simultaneously measuring the real and reactive power delivered to an AC load.
an instrument for measuring electric power in watts. A wattmeter requires connections to measure both the current through and the voltage across the load being measured.
Weber, Wilhelm (1804-1891) Born: Wittenberg, Germany

is best known as the person who deduced that electricity consists of charged particles. Weber held several university appointments including professorships at Gottingen, where he had a very productive collaboration with Karl Gauss. Weber insisted on precision in his mathematical and experimental work. He developed a number of very precise measurement instruments. His efforts helped establish a sound foundation for the study of electricity and magnetism. He is honored by having his name used as the SI unit of magnetic flux density, the weber.
Weber's law
an experimental result that states that the smallest luminance increment ΔL at which a region of luminance L + ΔL is just discernible from a background of luminance L is such that the ratio ΔL/L is constant. See also brightness constancy, simultaneous contrast.
Westinghouse, George (1846-1914) Born: Central Bridge, New York, U.S.A.

is best known as a financier and industrialist during America's age of great commercial expansion. What is less
known today is that Westinghouse's fortune was based on his early inventions in the railroad industry. His braking system was eventually adopted in most rail cars. Westinghouse went on to secure over 400 patents in the rail and the gas distribution industries. Before hiring Tesla and buying his patents, Westinghouse had been a champion of alternating current for power distribution. His company provided illumination for the great Chicago Exposition of 1893. Before
his death, Westinghouse was to lose control of the companies that bear his name. Undaunted, he returned to the laboratory for a number of additional years of invention.
Wheatstone bridge
a bridge circuit where all arms are resistors. The condition of balance in the circuit is used for precise measurement of resisors. In this case, one of the arms is an unknown resistor, another arm is a standard resistor (usually a variable resistor box), and two other arms (called ratio arms) are variable resistors with a well determined ratio. When the condition of balance is achieved, one can calculate the unknown resistor multiplying the standard resistor value by the ratio of ratio arms resistors. The precision of measurements is 0.05% for the range 10 ohms to 1 megohm.

The Wheatstone bridge is used for resistor measurements at DC and AC (in the universal impedance bridges).

Moreover, the Wheatstone bridge is widely used in resistive transducers where one or more arms is substituted by resistors
the resistance of which depends on a physical variable (temperature, pressure, force, etc.). In these applications, the deflection from balance is used for measurement of the physical variable.
wind farm
a plot of land on which several power-generating windmills are placed.
wind power generator
a system that utilizes the energy in the wind to generate electricity. The energy in the wind drives a wind turbine which acts as the prime mover for the generator. A wind turbine operates at a variable speed, and an appropriate electric machine and controller converts the mechanical energy into electrical energy and pumps it into a utility grid.
wind-electric conversion
the process by which wind (mechanical) energy is converted to electrical energy, usually by the use of wind turbine.
a conductive path, usually wire, inductively coupled to a magnetic core or cell.
winding factor
a design parameter for electric machines that is the product of the pitch factor and the distribution factor.
wiped joint
a fused joint used in splicing lead-sheathed cables.
withstand test
a test of an insulator's ability to withstand a high voltage of some specified waveform.
wound rotor induction motor
an induction motor in which the secondary circuit consists of a polyphase winding or coils connected through a suitable circuit. When provided with slip rings, the term slip-ring induction motor is used.
pre-formed wire grips or ties for mechanically joining overhead conductors to insulators.