Reactive Power

(1) electrical energy per unit time that is alternately stored, then released. For example, reactive power is associated with a capacitor charging and discharging
as it operates on an AC system. Symbolized byQ, with units of volt-amperes reactive (VAR), it is the imaginary part of the complex power.

(2) the power consumed by the reactive part of the load impedance, calculated by multiplying the line current by the voltage across the reactive portion of the load. The units are vars (volt-ampere reactive) or kilovars.

Phase Shifter

A device that changes the phase angle between two buses in a power system. Conventional phase shifters are special autotransformers in with each phase  voltage in connected in series with a variable component of voltage from another phase.

Phase Sequence

Describes the rotational orientation of the voltage phasors in a 3-phase electrical power system. A positive phase sequence, designated by the nomenclature ABC, indicates a 3-phase connection in which the B phase voltage lags the A phase voltage by 120 degrees, and the C phase voltage leads the A phase voltage by 120 degrees. A negative phase sequence, designated by ACB, reverses this  relationship so that the B phase leads the A phase, and the C phase lags the A phase.

Permeability

Tensor relationship between the magnetic field vector and the  magnetic flux density vector in a medium with no hysteresis; flux density divided by the magnetic field in scalar media. Permeability indicates the ease with which a magnetic material can be magnetized. An electromagnet with a higher permeable core material will produce a stronger magnetic field than one  with a lower permeable core material. Permeability is analogous to conductance, when describing electron flow through a material.

Permanent Split-capacitor (PSC) Motor

A induction motor that operates from a singlephase supply. The motor contains two phase windings in quadrature; however, one of them has a capacitor in series with it to create a phase shift between the winding currents. Both windings and the capacitor operate continuously so the machine acts like a two-phase machine when running at its operating speed, producing less vibration and noise than a single-phase motor. Since the capacitor runs continuously, it is sized smaller than the capacitor used in a capacitor-start induction motor (CSIM). Thus, the PSC motor produces a lower starting torque than the CSIM.

Permanent Magnet Brushless DC Machine

A machine that is similar in structure to a permanent magnet synchronous machine, containing armature windings on the stator and permanent magnets on the rotor. The permanent magnet brushless DC machine, however, is characterized by a trapezoidal flux density distribution in the airgap instead of
the sinusoidal distribution of the synchronous machine. In operation, a DC  voltage is applied sequentially to the stator coils to create a rotating field that pulls the rotor with it. To correctly operate, the brushless DC machine requires sensors to determine the rotor position so that the proper stator phases may be excited.

Ohm, Georg Simon (1789–1854)

Born: Erlangen, Germany
Ohm is best known for his discovery of what we now call Ohm’s Law. Ohm held a variety of teaching posts at secondary schools as well as universities. In 1827 he published his greatest work, Die Galvanische Kette. Along with Andre Ampere, Ohmwas the first to publish rigorously mathematical and theoretical work on electricity. Ohm’s famous law states that current in a resistor is  proportional to the applied voltage and inversely proportional to the resistance. Ohm’s work was initially scorned because it lacked the experimental evidence.  Worldwide acclaim changed Ohm’s fortunes several years later.
He is honored by having his name used asthe unit of resistance, the ohm, and the unit of conductivity, the mho.

Ohm’s Law

A fundamental law which states that the voltage across a resistance is directly proportional to the current flowing through it. The constant of proportionality is
known as the resistance. This concept can be generalized to include the relationship between the voltage and current in all situations, including  alternating voltages and currents. In this case, all the quantities are measured as complex numbers, known as phasors, that are functions of frequency. This broadens the basic definition of resistance, which is a real number measured in ohms, to that of impedance, which is a complex number with magnitude  measured in ohms and phase angle in degrees. The real part of the complex number representing impedance is the resistance while the imaginary part is the reactance. Ohm’s Law is a central concept to most electrical engineering
theories.

Induction Voltage Transformer

Specially constructed transformer with a rotating primary coil that is used to provide voltage regulation on individual power circuits. The secondary of an induction regulator is mounted on the stationary shell of cylindrical core, and the primary is mounted on a movable, center rotor. In the neutral position, the  magnetic axes of the primary and secondary coils are oriented 90 degrees to each other, reducing the magnetic coupling to zero. In this position, energizing the primary does not induce voltage in the secondary; however, rotating the primary coil in either direction from the neutral position creates mutual flux linkage and causes a secondary voltage to appear. Rotation in one direction causes secondary
voltage to be in phase with the primary; rotation in the opposite direction causes secondary voltage to be out of phase with the primary. Voltage regulation is  provided by connecting the primary coil across the line to be regulated and connecting the secondary coil in series with the load. By positioning the primary coil based on load demand in the line, secondary voltage can be used to adjust line voltage either up or down. Induction regulators are also equipped with a
short-circuited coil mounted on the primary in spatial quadrature with the primary coil. In the neutral position, this coil has maximum coupling with the secondary coil, which minimizes the inductive reactance in the load line due to the secondary coil.

Ideal Transformer

A transformer with zero winding resistance and a lossless, infinite permeability  core resulting in a transformer efficiency of 100 percent. Infinite permeability would result in zero exciting current and no leakage flux. For an ideal   transformer, the ratio of the voltages on the primary and secondary sides would be exactly the same as the ratio of turns in the windings, while the ratio of currents would be the inverse of the turns ratio.

Hysteresis Motor

Any of a variety of single-phase AC motors that use the hysteresis properties of hard magnetic materials to develop torque. Stator windings of a hysteresis motor can be of any design that produces a rotating flux within the machine. Motion of
the rotating flux over the rotor magnetizes the hard magnetic material on the  rotor; however, the hysteresis characteristics of the material cause the alignment of magnet flux to lag the rotating stator flux. This misalignment produces rotor torque. Because of the nature of the torque production, hysteresis motors operate at synchronous speed and have a constant torque characteristic, which permits them to synchronize any load that they can accelerate.

Hysteresis

(1) the phenomenon that the magnetic state of a substance is dependent upon its magnetic history, so that its magnetization for an increasing magnetizing force differs from that for a decreasing magnetizing force.

(2) the characteristic of magnetic materials that causes the trajectory of the flux density vs. field intensity curve as the intensity is increased to be different from that when the intensity is decreased, giving rise to a loss, which is proportional to the area enclosed by the two trajectories.

Hysteresis Brake
A braking device utilizing hysteresis to provide a constant braking torque irrespective of slip speed.

Faraday, Michael (1791–1867)

Born: Newington, Surrey, England
Faraday is best known as the greatest experimental physicist of the 19th century. It was Faraday who invented the electric motor, generator, and transformer, and first described electromagnetic induction and the laws of electrolysis. Faraday had no formal schooling, although he attended many lectures. The most  inspirational of these lectures were by the famed chemist Sir Humphry Davy. Faraday became Davy’s assistant and thus began an extraordinary career as an  experimentalist. Faraday’s contributions are recognized by the use of his name as he unit of electrical capacitance, the farad in the SI system, and the Faraday  constant in electrolysis.

Faraday’s Law

One of Maxwell’s equations that describes the fundamental relationship between induced voltage and a time varying magnetic field. For a conducting coil, the induced voltage is proportional to the time rate of change in the magnetic flux linking the coil. This change may be produced either by actual variation of field strength or by relative motion between coil and field.

Electromagnetic Interference (EMI)

(1) any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of a spurious emissions and responses,  intermodulation products, and the like. Additionally, EMI may be caused by atmospheric phenomena, such as lightning and precipitation static and non-telecommunication equipment, such as vehicles and industry machinery.

(2) unwanted high-frequency electrical signals, also known as radio frequency interference (RFI), which can be generated by power electronic circuits switching at high frequencies. The signals can be transmitted by conduction along cables (450 kHz to 30 MHz) or by radiation (30MHzto 40 GHz) and can interfere with control or other electronic equipment.

Dynamo

A term used to describe any of a variety of rotating machines that convert mechanical to electrical energy, or less commonly, electrical to mechanical  energy. Dynamos typically consist of a stationary structure, called the stator, supporting a rotating element called the rotor. Energy conversion occurs via Faraday induction. A field winding (or in some smaller machines, permanent
magnets) is mounted on one of the mechanical structures and produces a  magnetic flux. An armature winding is mounted on the other structure, and rotation of the rotor produces relative motion between the field flux and the coils of an armature winding, inducing a Faraday voltage in the armature coil. This Faraday induced voltage is the source of electrical energy at the dynamo output.

Current Transformer (CT)

(1) a transformer that is employed to provide a secondary current proportional to primary current flowing. The primary “winding” is often created by passing the system conductor or bus bar through an opening in the device and the secondary is typically rated at a standard value to match common meters and display units. Current transformers are used in current measurement, protective relays, and power metering applications. The load (meter) on a CT should never be removed without first shorting the secondary of the CT, otherwise dangerous voltage levels may result when the load is removed.

(2) a device which measures the instantaneous current through a conductor of an electric power line and transmits a signal proportional to this current to the power system’s instrumentation.

Constant-Current Transformer

Two-coil transformer with a moveable secondary coil used to provide constant output current to a variable load. Constant current is maintained by mounting both the primary and secondary coils on the center element of a shell type core and allowing the secondary coil to move up and down with changes in demand
for load current. Increasing current demand due to a reduction in load impedance causes the secondary coil to move away from the primary coil. Increasing the coil separation increases flux leakage and reduces the secondary output voltage. The reduced output voltage counteracts the demand for more current. Increases in load impedance reverse the process. Movement of the secondary coil is controlled automatically by attaching the secondary coil to a counterweight and pulley assembly and orienting the coil windings such that their flux directions oppose. Increases in secondary current increase the magnetic repulsion between the coils, which, aided by the counterweight, moves the secondary coil away from the primary. Reductions in secondary current produce the opposite effect.

Commutation

The process by which alternating current in the rotating coil of a DC machine is converted to unidirectional current. Commutation is accomplished via a set of stationary electrical contacts (brushes) sliding over multiple, shaft-mounted  electrical contacts that turn with the machine rotor. The contacts are the  connection points in a series-connected loop of the coils that make up the rotor winding. The brushes, sliding over these contacts, continually divide the loop into two parallel electrical paths between the brushes. The brushes are positioned such that they make contact with those commutator segments that are connected to coils that are moving through a magnetic neutral point between poles of the machine’s field flux. As a result, all coils making up one parallel path are always moving under a north magnetic pole, and the others are always moving under a south magnetic pole. The movement of the commutator contacts underneath the brushes automatically switches a coil from one path to the other as it moves from a north pole region to a south pole region. Since the coils in both paths move in the same direction, but through opposite flux regions, the voltages induced in the two paths are opposite. Consequently, the positive and negative ends of each path occur at the same points in the series loop, which are at the points where the brushes contact the commutator. The brush positions, thus, represent a  unidirectional (or DC) connection to the rotating coil.

Centrifugal Switch

A speed-sensitive switch operated by centrifugal force, mounted on the shaft of a motor, used to perform a circuit switching function. Used in single-phase induction motors to disconnect the starting winding when the motor approaches operating speed.

Capacitance

The measure of the electrical size of a capacitor, in units of farads. Thus a capacitor with a large capacitance stores more electrons (coulombs of charge)
at a given voltage than one with a smaller capacitance.

 In a multiconductor system separated by nonconductive mediums, capacitance (C) is the proportionality constant between the charge (q) on each conductor and the voltage (V ) between each conductor. The total equilibrium system charge is zero. Capacitance is dependent on conductor geometry, conductor spatial relationships, and the material properties surrounding the conductors.

 Capacitors are constructed as two metal surfaces separated by a nonconducting electrolytic material. When a voltage is applied to the capacitor the electrical charge accumulates in the metals on either side of the nonconducting material, negative charge on one side and positive on the other. If this material is a fluid then the capacitor is electrolytic; otherwise, it is nonelectrolytic.

Bus

(1) a data path connecting the different subsystems or modules within a computer
system. A computer system will usually have more than one bus; each bus will
be customized to fit the data transfer needs between the modules that it connects.

(2) a conducting system or supply point, usually of large capacity. May be composed of one or more conductors, which may be wires, cables, or metal bars (busbars).

(3) a node in a power system problem

(4) a heavy conductor, typically used with generating and substation equipment.

Buck-Boost Transformer

A special purpose 2- or 4-coil transformer used to produce modest increases or decreases in the utilization voltage at a load site. The low-voltage coil(s), which typically have rated voltages of 5% to 15% of the high-voltage coils, and in use, the high- and low-voltage, coils, are connected in series to produce an  autotransformer arrangement. If primary voltage is applied to the high voltage coil and load voltage is taken from the series coil combination, the low-voltage coil adds to, or boosts, the load utilization voltage. Conversely, reductions in load utilization voltage occur when these primary and secondary connections are reversed causing the low-voltage coil to buck the supply voltage. A typical 4-coil buckboost transformer would have two 120 V primary coils and two 12 V secondary coils, which could be used to produce voltage ratios of (120/132), (120/144), (240/252), and (240/264). In a basic buck-boost converter, the  inductor accumulates energy from the input voltage source when the transistor is on and releases energy to the output when the transistor is off. It can be viewed as a buck converter followed by a boost converter with topologic simplification. In a buck-boost converter, the output voltage vo is related to the input voltage vi by vo = vid/(1 − d) and it can be controlled by varying the duty ratio d. Note
that the output voltage is opposite polarity to the input. Also called a buck-boost converter, up-down transformer or up-down converter

Braking

Operating condition in an electric motor in which the torque developed between
the stator and rotor coils opposes the direction of rotation of the rotor. Typical braking methods in DC machines include “plugging” in which the polarity of either the field or the armature coil, but not both, is reversed while the rotor is turning, “dynamic braking” in which generator action in the armature is used to dissipate rotor energy through a braking resistor, and “regenerative braking” in which generator action in the rotor is used to dissipate rotor energy by returning
electric power to the power source as the rotor slows. Typical braking methods in AC machines include switching of the phase sequence of the supply voltage, dynamic braking through the armature coils, and varying the frequency of the AC supply voltage.

Bipolar junction transistor (BJT)

A three-terminal nonlinear device composed of two bipolar junctions (collector-base, baseemitter) in close proximity. In normal operation, the voltage between base and emitter terminals is used to control the emitter current. The collector current either equals this (with BC junction in reverse bias), or goes into saturation (the BC junction goes into forward bias). Used for medium power (700 A) and medium speed (10 kHz) applications. In power electronics applications, BJTs are typically operated as switches, in either
their fully on or off states, to minimize losses. The base current flowing into the middle of the device controls the on–off state, where continuous base current is required to be in the on state. A disadvantage is the low current gain.
The base current is generally much smaller than collector and emitter currents,
but not negligible as in MOSFETs.

Ayrton, William Edward (1847–1908)

Born: London, England
Ayrton is best known as the inventor of a number of electrical measurement devices and as an engineering educator. Ayrton’s early work was with the Indian Telegraph Service, after which he studied with William Thomson (Lord Kelvin) in Glasgow. After several more telegraph assignments Ayrton traveled to Tokyo, where he established the first electrical engineering teaching laboratory at the Imperial Engineering College. Among his many inventions he is credited with the ammeter and an improved voltmeter. His wife Bertha was also an active researcher and became the first woman to be admitted to the Institute of Electrical Engineers.

Auto Transformer

A power transformer that has a single continuous winding per phase, part of this winding being common to both the primary and the secondary sides. As a result, these voltages are not isolated but the transformer is reduced in weight and size. Autotransformers are most suited for relatively small changes in voltage. Three phase autotransformers are by necessity connected in a wye configuration.

Autonomous System

A dynamic system described by a first-order vector differential equation that is unforced and stationary. In other words, such a system is governed by an equation of the form

x(t) = f(x(t))

Apparent Power

(1) in an AC system, the product of voltage, E and current, I . Apparent power (or total power) is composed of two mutually independent components—an active component (real power), and a reactive component (imaginary power).  Apparent power is denoted by S, and has the unit of volt-amperes.

(2) the scalar product of the voltage and current delivered to the load. It can also be expressed as the vector S= P + jQ, where P = real power and Q = reactive power.

ANSI (American National Standards Institute)

ANSI American National Standards Institute, a body which administers numerous industrial standards in the USA including several which pertain to electric utility construction practices.

Ampere, Andre Marie (1775–1836)

Born: Lyon, France
Ampere is best known for his pioneering work in the field of Electrodynamics. During his emotionally troubled life, he held several professorships: at Bourg, Lyon, and at the Ecole Polytechnic in Paris. While Ampere worked in several sciences, the work of the Danish physicist Hans Christian Oerstad on the electric deflection of a compass needle, as demonstrated to him by Dominique Arago,
caused Ampere’s great interest in electromagnetism. His seminal work, Notes on the Theory of Electrodynamic Phenomena Deduced Solely from Experiment, established the mathematical formulations for electromagnetics including what is now known as Ampere’s Law. It can be said that Ampere founded the field of electromagnetics. He is honored for this by the naming of the unit of electric current as the ampere.

Advanced Mobile Phone System (AMPS)

A standard for a cellular radio communications network originally developed in the 1970s by AT&T and later adopted as an industry standard by the U.S.-based Telecommunications Industries Association (TIA). It is the first cellular standard widely deployed in North America. It is also referred to as the analog cellular system. Frequency modulation with 30 kHz channels is used.

Active Network

An electrical network that contains some solid state devices such as bipolar junction transistors (BJTs) or metal oxide-silicon field effect transistors (FETs)
operating in their active region of the voltage vs. current characteristic. To ensure that these devices are operating in the active region, they must be supplied with proper DC biasing.

AC Coupling

A method of connecting two circuits that allows displacement current to
flow while preventing conductive currents. Reactive impedance devices (e.g., capacitors and inductive transformers) are used to provide continuity of alternating current flow between two circuits while simultaneously blocking the flow of direct current.

Exciting Current

The current drawn by a transformer primary with its secondary open circuited. It is the vector sum of the core loss current Ic and the magnetizing branch current
Im. The exciting current Ie is also the current measured in the open circuit test on
a transformer. The exciting current is calculated as the ratio of the primary induced EMF and the impedance of the tank circuit. On load, it is equal to the difference between the primary and reflected secondary currents of the transformer.

Edison, Thomas Alva (1847–1931)

Born: Milan, Ohio, U.S.A.
Edison is best known as the holder of 1069 patents secured during his lifetime.  Among these were patents for the phonograph and the incandescent filament lamp. Edison was largely self-taught. His early interest in communication devices stemmed from his employment as a telegraph operator. He used
the profits from the sale of his first invention, a “stock ticker,” to set up a lab in Newark, New Jersey. Always a shrewd commercial developer, he followed the invention of the light bulb with work on developing efficient generators to power these bulbs. Edison is considered the archetypal American inventive genius.

Coulomb’s Law

The force of repulsion/attraction between two like/unlike
charges of electricity concentrated at two points in an isotropic medium is proportional to the product of their magnitudes and inversely proportional to the square of the distance between them and to the dielectric constant of the medium.

Sources of Electricity

Electricity can be created by several means: Friction, Heat, Light, Pressure, Chemical Action, or Magnetic Action.

Only a few of these sources of energy are used in the automobile. The battery produces electricity through chemical action, and the alternator produces electricity through magnetic action.

Friction creates static electricity.
Heat can act upon a device called a thermo couple to create DC.
Light applied to photoelectric materials will produce DC electricity.
Pressure applied to a piezoelectric material will produce DC electricity.
Chemical Action of certain chemicals will create electricity.

Alternating Current (AC)

Electricity with electrons flowing back and forth, negative - positive- negative, is called Alternating Current, or AC.

The electrical appliances in your home use AC power.

Direct Current (DC)

Electricity with electrons flowing in only one direction is called Direct Current or DC.
DC electrical systems are used in cars.

What Is Dynamic Electricity

Dynamic Electricity is electricity in motion, meaning you have electrons flowing, in other words voltage potential with electron flow.

Two types of dynamic electricity exists:
Direct Current (DC)
Alternating Current (AC)

Static Electricity

Voltage potential with NO electron flow.

Example: By rubbing a silk cloth on a glass rod, you physically remove electrons from the glass rod and place them on the cloth. The cloth now has a surplus of electrons (negatively charged), and the rod now has a deficiency of electrons (positively charged).

Another example: Rub your shoes on a rug and then touch a metal table or chair .... Zap!! The shock you felt was the static electricity dissipating through your body.

Types of Electricity

Two basic types of Electricity classifications:

STATIC ELECTRICITY is electricity that is standing still. Voltage potential with NO electron flow.

DYNAMIC ELECTRICITY is electricity that is in motion. Voltage potential WITH electron flow. Two types of Dynamic electricity exist:

    Direct Current (DC) Electron Flow is in only one direction.

    Alternating Current (AC) Electron flow alternates and flows in both directions (back and forth).

Effects of Current Flow

Two common effects of current flow are Heat Generation and Electromagnetism.
HEAT: When current flows, heat will be generated. The higher the current flow the greater the heat generated. An example would be a light bulb. If enough current flows across the filament, it will glow white hot and illuminate to produce light.
ELECTROMAGNETISM: When current flows, a small magnetic field is created. The higher the current flow, the stronger the magnetic field. An example: Electromagnetism principles are used in alternators, ignition systems, and other electronic devices.

Electron Theory

The Electron Theory states that current flows from NEGATIVE to POSITIVE. Electrons move from atom to atom as they move through the conductor towards positive.

Semiconductor

Any material with exactly 4 free flectrons in the outer orbit are called SEMICONDUCTORS.
A semiconductor is neither a conductor or insulator.
semiconductor material includes carbon, silicon, and germanium.
These materials are be used in the manufacturer of diodes, transistors, and integrated circuit chips.

Conductor

A CONDUCTOR is any material that easily allows electrons (electricity) to flow.
A CONDUCTOR has 1 to 3 free electrons in the outer ring.Because atoms with 1 to 3 electrons in the outer ring are held (bound) loosely to the atom, they can easily move to another atom or make room for more electrons.
Conductor material includes copper and gold.

Insulator

An INSULATOR is any material that inhibits (stops) the flow of electrons (electricity).
An insulator is any material with 5 to 8 free electrons in the outer ring.Because, atoms with 5 to 8 electrons in the outer ring are held (bound) tightly to the atom, they CANNOT be easily moved to another atom nor make room for more electrons.
Insulator material includes glass, rubber, and plastic.

Electrical Resistance

Electrical resistance is the repulsion of a current within a circuit. It explains the relationship between voltage (amount of electrical pressure) and the current (flow of electricity).

Resistance, discovered by Georg Simon Ohm in 1827, is the ratio between voltage and current. Ohm's law said that the voltage between any two points in a conductor changes directly as the current between the two points, given the temperature remains the same and does not change.

Potential Difference or Electromotive Force

Potential difference is the amount of work energy required to move an electric charge from one point to another.

The unit of potential difference is the volt (V)

Current

Current is a flow of electrical charge carriers, usually electrons or electron-deficient atoms. The common symbol for current is the uppercase letter I. The standard unit is the ampere, symbolized by A. One ampere of current represents one coulomb of electrical charge (6.24 x 1018 charge carriers) moving past a specific point in one second. Physicists consider current to flow from relatively positive points to relatively negative points; this is called conventional current or Franklin current. Electrons, the most common charge carriers, are negatively charged. They flow from relatively negative points to relatively positive points.