Delmar's Definitions T thru

Unity

100%, or 1.

Thermal fuse

A fuse designed to open due to excessive heat.

Voltage surge

A momentary increase of voltage lasting 50 microseconds or less.

True power

generally expressed as watts. Describes the amount of electrical energy converted into some other form.

Torque motor

motor designed to operate with the rotor stalled without damage to the motor.

Unidirectional

moving in only one direction.

Three-phase VARs

reactive power in a three-phase circuit.

Wire-wound resistors

resistors that are constructed by winding resistive wire around a nonconductive material.

Wattless power

see reactive power

Three-phase bank

single-phase transformers connected in such a way as to operate on a three-phase system.

Useful static charges

static electric charges that are intentionally placed on objects.

Time constant

the amount of time required for the current flow through an inductor or for the voltage applied to a capacitor to reach 63.2% of its total value.

Tolerance

the amount of variation from a standard value that is permissible.

Voltage drop across the capacitor

the amount of voltage measured across a capacitor.

Voltage drop across the resistor

the amount of voltage measured across a resistor.

Voltage drop

the amount of voltage required to cause an amount of current to flow through a certain resistance.

Tangent

the angular relationship of the opposite side of a right triangle and the adjacent side.

Windage loss

the losses encountered by the armature or rotor of a rotating machine caused by the friction of the surrounding air.

Turns of wire

the number of turns of wire in a coil.

Triplen harmonics

the odd multiples of the third harmonic.

Voltage polarity

the polarity of the voltage at a particular point in a circuit. Generally of concern in direct current circuits.

Turns ratio

the ratio of the number of turns in the primary winding of a transformer as compared to the turns of wire in the secondary winding.

Zener region

the region of a semiconductor device that is reached when current flows through it in the reverse direction.

Waveform

the shape of a wave as obtained by plotting a graph with respect to voltage and time.

Three-phase watts

the true power in a three-phase system. The formula used is dependent on whether line or phase values of voltage and current are to be employed.

Torque

the turning force developed by a motor.

Total voltage

the voltage applied to the circuit.

Troubleshoot

to locate and eliminate problems in a circuit.

Total current (IT)

total amount of current flow in a circuit.

Trace the current path

tracing the path of current through a circuit.

Thermal overload relay

An overload relay that senses motor current by connecting a heater in series with the motor.

Unity power factor

a power factor of 1 (100%). Unity power factor is accomplished when the applied voltage and circuit current are in phase with each other.

Two-phase

a power system that contains two phases 90deg out-of-phase with each other.

Voltage rating

a rating that indicates the amount of voltage that can be safely connected to a device.

Temperature relay

a relay that functions at a predetermined temperature. Generally used to protect some other component from excessive temperature.

Varistor

a resistor that changes its resistance value with a change of voltage.

Thermistor

a resistor that changes its resistance with a change of temperature.

Variable resistor

a resistor whose resistance value can be varied between its minimum and maximum values.

Thevenin's theorem

used to reduce a circuit to a single voltage source and a series resistor.

Transistor

a solid-state device made by combining three layers of semiconductor material together. A small amount of current flow through the base-emitter can control a larger amount of current flow through the collector-emitter.

Valence electrons

electrons located in the outer orbit of an atom.

Termination temperature

The temperature of an electrical termination.

TRIAC

a bidirectional thyristor used to control AC voltage.

Trimmer capacitor

a capacitor that can be adjusted over a narrow range of values.

Voltage divider

a circuit that generally is constructed by connecting resistors in series to produce desired voltage drops across the resistors.

Wheatstone bridge

a circuit used to accurately measure resistance.

Thundercloud

a cloud that contains charged particles.

Wye connection

a connection of three components made in such a manner that one end of each component is connected. This connection is generally used to connect devices to a three-phase power system.

Tape-wound core

a core made by winding a continuous length of magnetic metal into a spiral.

Zenith

a culmination or high point.

Thermocouple

a device for producing a voltage due to a difference of temperature.

Voltage regulator

a device or circuit that maintains a constant value of voltage.

Voltaic cell

a device that converts chemical energy into electric energy.

Transducer

a device that converts one type of energy into another type of energy. For example, a solar cell converts light into electricity.

Zener diode

a diode that has a constant voltage drop when operated in the reverse direction. Zener diodes are commonly used as voltage regulators in electronic circuits.

Toroid core

a doughnut-shaped electromagnet.

Terminal

a fitting attached to a device for the purpose of connecting wires to it.

Voltaic pile

a group of voltaic cells connected together to form a battery.

Vector

a line having a specific length and direction.

Triangle wave

a linear wave form.

Volt (V)

a measure of electromotive force. The potential necessary to cause 1 coulomb to produce 1 joule of work.

Weber (Wb)

a measure of magnetic lines of flux in the MKS (Meter-Kilogram-Second) system. 1 Wb 5 100 million lines of flux.

Watt (W)

a measure of true power.

Wattmeter

a meter used to measure true power or watts.

Vector addition

a method of adding angles.

Tagging

a method of identifying conductors or components.

Tera-

a metric prefix meaning one trillion (10 to the 12th power)

Voltage spike

a momentary increase of voltage lasting 2 nanoseconds or less.

Volt-ohm-milliammeter (VOM)

a test instrument designed to measure voltage, resistance, or milliamperes.

Wound-rotor motor

a three-phase motor containing a rotor with windings and sliprings. This rotor permits control of rotor current by connecting external resistance in series with the rotor winding.

Wye-delta

a three-phase transformer connection that has its primary connected in wye and a secondary connected in delta.

Universal motor

a type of motor that can be operated on AC or DC power.

Warren motor

a type of single-phase synchronous motor.

Wound rotor

a type of three-phase rotor that contains phase winding and slip rings.

Tesla (T)

a unit of magnetic measure in the MKS system. 1 Tesla = 1 weber per square meter.

Watt-hour (W-hr)

a unit of measure for describing the current capacity of a battery or a cell.

Vacuum-tube voltmeter (VTVM)

a voltmeter that uses the grid of a vacuum tube to produce a very high input impedance. VTVMs are used in electronic circuits to prevent loading the circuit that is being tested. Modern VTVMs replace the vacuum tubes with field-effect transistors (FETs).

VTVM

abbreviation for vacuum-tube voltmeter.

Zone

an area, region, or division distinguished from adjacent parts or objects by some feature, characteristic, or barrier.

Transformer

an electric device that changes one value of AC voltage into another value of AC voltage.

Wiring diagram

an electrical diagram used to show components in their approximate physical location with connecting wires.

Voltage

an electrical measurement of potential difference, electrical pressure, or electromotive force (EMF).

Thyristor

an electronic component that has only two states of operation, on and off.

Tank circuit

an inductor and capacitor connected in parallel.

Trimmer inductor

an inductor that can be adjusted over a narrow range of values.

Voltmeter

an instrument used to measure a level of voltage.

Wet locations

areas that are subject to saturation with water or other liquids.

Wave-wound armatures

armatures that have their windings connected in such a way as to form a series connection.

X-rays

beams of high-energy protons.

Variable capacitors

capacitors whose value can be changed.

Volts-per-turn ratio

determined by dividing the voltage applied to the primary of a transformer by the number of turns of wire in the primary.