Thursday, March 19, 2009
Letter Z
Zener: It is used to make votahe stable at certain fix volt,it always operate under reverse bias condition
Letter W
Watt
The basic unit of electric power. The symbol for watt is “W.”
Word
Usually one or more bytes used to represent instructions or
data in digital equipment.
Wye
A connection arrangement used for the primary and/or
secondary of a three-phase transformer.
The basic unit of electric power. The symbol for watt is “W.”
Word
Usually one or more bytes used to represent instructions or
data in digital equipment.
Wye
A connection arrangement used for the primary and/or
secondary of a three-phase transformer.
Letter Vo
Volt
The basic unit of voltage. The symbol for volt is “V.”
Voltage
Also called difference of potential, electromotive force, or EMF.
Voltage is a force that, when applied to a conductor, causes
current to flow. Voltage is symbolized by “E” or “V” and is
measured in volts.
Voltmeter
A meter designed to measure voltage.
Volts per Hertz (V/Hz)Operation
Describes the operation of many variable frequency drives that
control the speed of an AC motor by varying the frequency of
the voltage applied to the motor while maintaining a constant
voltage to frequency ratio.
Letter V
Var
The basic unit for reactive power. Shortened from volt-ampere
reactive.
Variable Frequency Drive (VFD)An electronic device used to control the speed a of an AC
motor. A VFD controls the motor speed by varying the
frequency and voltage applied to the motor. Also called an AC
drive.
Variable Speed Drive An electronic drive device used to control the speed of an electric motor. This term applies to both AC Drives and DC
Drives.
Vector Control
A technique employed by some variable frequency drives that
involves calculations of AC motor current vectors and precise
control of motor flux to provide excellent speed and torque
control.
Letter Tr
Transformer
Coils of wire wound on a common frame that allow electrical
energy to be transferred from one circuit to another.
Transformers used in low frequency applications are commonly
wound around an iron core to improve energy transfer.
Transistor
A semiconductor device which usually has three terminals
although the names of the terminals are different for different
types of transistors. Some types of transistors are used as
electronic switches.
Trim
The front cover of a panelboard which includes an access door.
Trip Unit
The part of the circuit breaker that determines when the
breaker will trip. Many circuit breakers use a thermal-magnetic
or magnetic-only trip unit. Other circuit breakers have a solidstate
trip unit with multiple adjustments to custom fit the circuit
breaker’s time current curve to the application.
True Power
Also called real power, true power is the power dissipated by
circuit resistance. True power is equal to I2R and is measured in
watts. True power is also equal to the apparent power multiplied
by the power factor.
Coils of wire wound on a common frame that allow electrical
energy to be transferred from one circuit to another.
Transformers used in low frequency applications are commonly
wound around an iron core to improve energy transfer.
Transistor
A semiconductor device which usually has three terminals
although the names of the terminals are different for different
types of transistors. Some types of transistors are used as
electronic switches.
Trim
The front cover of a panelboard which includes an access door.
Trip Unit
The part of the circuit breaker that determines when the
breaker will trip. Many circuit breakers use a thermal-magnetic
or magnetic-only trip unit. Other circuit breakers have a solidstate
trip unit with multiple adjustments to custom fit the circuit
breaker’s time current curve to the application.
True Power
Also called real power, true power is the power dissipated by
circuit resistance. True power is equal to I2R and is measured in
watts. True power is also equal to the apparent power multiplied
by the power factor.
Letter Ti
Timing Relay
A control relay that incorporates a preset delay in contact
response. Some timing relays begin the time delay when the
relay is energized. Others begin the time delay when the relay
is de-energized.
Torque
A turning or twisting force. Since torque is expressed as a force
times the length of the radius at which the force is measured,
torque is represented in compound units such as pound-feet
(lb.-ft.)
Totally Enclosed Fan Cooled (TEFC )A motor enclosure type that restricts the flow of air into or out of the motor, but uses a fan to blow air over the
motor’s exterior.
Totally Enclosed Non-ventilated (TENV) A motor enclosure type that restricts the flow of air into or out of the motor. Because there are no ventilating openings, all
heat generated by the motor must be dissipated by conduction
through the encl
A control relay that incorporates a preset delay in contact
response. Some timing relays begin the time delay when the
relay is energized. Others begin the time delay when the relay
is de-energized.
Torque
A turning or twisting force. Since torque is expressed as a force
times the length of the radius at which the force is measured,
torque is represented in compound units such as pound-feet
(lb.-ft.)
Totally Enclosed Fan Cooled (TEFC )A motor enclosure type that restricts the flow of air into or out of the motor, but uses a fan to blow air over the
motor’s exterior.
Totally Enclosed Non-ventilated (TENV) A motor enclosure type that restricts the flow of air into or out of the motor. Because there are no ventilating openings, all
heat generated by the motor must be dissipated by conduction
through the encl
Letter T
Thermal-Magnetic
Used to describe a device that uses both heat and magnetism
as part of its operating principles. For example, a thermalmagnetic
circuit breaker can be tripped either by heat or
magnetic force resulting from an overcurrent.
Thermistor
A device used to sense temperature that varies in resistance as
temperature changes.
Thyristor
A family of multi-layer semiconductor devices that includes
silicon controlled rectifiers (SCR), gate turnoff (GTO) thyristors,
and other similar devices. Thyristors are often used in rectifier or
power switching circuits.
Time-Current Curve
A graph showing how long before a circuit breaker will trip at
each level of fault current.
Used to describe a device that uses both heat and magnetism
as part of its operating principles. For example, a thermalmagnetic
circuit breaker can be tripped either by heat or
magnetic force resulting from an overcurrent.
Thermistor
A device used to sense temperature that varies in resistance as
temperature changes.
Thyristor
A family of multi-layer semiconductor devices that includes
silicon controlled rectifiers (SCR), gate turnoff (GTO) thyristors,
and other similar devices. Thyristors are often used in rectifier or
power switching circuits.
Time-Current Curve
A graph showing how long before a circuit breaker will trip at
each level of fault current.
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