AC - Alternating Current

ALTERNATING CURRENT (AC) - A current that flows back and forth between the source and load. The amplitude of the current varies from zero, through a positive peak, back through zero, through a negative peak, and back to zero. This occurs a specified number of times per second. (see Frequency) and often the current appears to be sinusoidal. (see Sine Wave)

ADJUSTSTABLE SPEED DRIVE (ASD) - Also known as a "DC Drive". A device to control the speed and efficiency of DC electric motors. The device operates by taking AC from the distribution system and rectifying it to power on a DC bus. The drive then controls the DC voltage level that powers the motor. Since the speed of a DC motor is proportional to the voltage level of the DC supply, the speed can be adjusted over a wide range. (see Inverter; Rectifier; AC Power; DC Power; Variable Frequency Drive)

AGM - Absorbent glass mat- a type of lead-acid battery construction

Ah -Amp Hour - a measure of current (measured in amperes drawn over time (measured in hours), typically used to describe battery capacity and battery charging or discharging.

AMBIENT TEMPERATURE - Temperature of the surroundings in which a piece of equipment is used or operated.

AMMETER - Meter for measuring the flow of current in an electrical circuit. Meters are available to measure AC or DC current. Low current measurements are often expressed in milliamperes (0.001 ampere) and higher currents are usually expressed in amperes. AC ammeters come in two main types: a "true rms ammeter" which measures rms current, and an "average responding, rms indicating ammeter" which only provides correct rms results when the current waveform is a sine wave. (see: Alternating Current; Direct Current, rms, fundamental.)

AMPERE - The unit of electrical current flow. Usually given the symbol "I", from the French "Intensity"." Related to voltage and resistance by Ohm's Law. Can be compared analogously to the flow of water in a pipe. The same unit is used for alternating current and for direct current, but they are measured differently. An ampere is often referred to as an "amp", or the letter "A"; eg: 103 Amps or 103A (see: Voltage; Resistance; Ohm's Law; Alternating Current; Direct Current; RMS/Root Mean Square)

AMPLITUDE - The height or value above or below the zero point reached by an AC waveform. (see: Alternating Current.)

AMPS - abbreviation for amperes.

APPARENT POWER - The total amount of power that must be delivered to a load to enable it to work. This includes the real power (useful power which does the work) and the reactive power (overhead, but necessary). Apparent Power = Real Power + Reactive power. Example: the Apparent Power necessary to turn a motor at a specific speed and torque consists of the Real Power (contributes to speed and torque) and the Reactive power (energizes the motor coil, but does not contribute to speed or torque). Apparent power is calculated by multiplying current times voltage. (Note that if the load is resistive, true power factor is unity and the apparent power equals the real power. If the true power factor is less than unity, apparent power will be greater than real power.) (see: Voltamp; Current; Watt; Power Factor; Real Power; Reactive Power.)

Battery cycle life - the number of discharge and recharge cycles that a battery can undergo before degrading below its capacity rating.

BEMF (Back-EMF) - the

*Electro-Magnetic Field*formed by a DC motor's coils passing its magnets; increases with RPMs, reducing the motor's ability to turn faster .

BEV -Battery Electric Vehicle- An EV powered by electricity stored in batteries.

BLDC -Brushless Direct Current - same as a brushless motor (see below).

BMS -Battery Management System - a circuit that protects battery cells against harmful operating conditions. Typically required for lithium batteries.

Brushed -Brushed DC Electric Motor, a motor that uses carbon brushes to switch the motor windings.

Brushless - Brushless DC motor, a motor that uses transistors to switch the motor windings.

C-rate - Battery "Current" expressed in terms of the battery capacity. For example, a 10 A-hr battery with a current of 10 amps would be running 1C. At 20 amps it would be 2C, etc. Applies to both charging and discharging.

Capacity - The amp-hour rating of a battery. Bigger batteries have more capacity.

CAPACITOR - A device that stores electrical charge. Alternating current capacitors are used to provide reactive power which leads the real power. Direct current capacitors are used to store power by holding charge. Capacitors resist a change in voltage. The unit used to measure capacitors is "farad." A farad, abbreviated "f" is a very large value, so the more common unit is "microfarad" (0.000001 f) or Ãƒâ€šÂµf. The relationship between farads and voltage results in the reactive unit "VAR" or "kVAR" which is another unit capacitors are also measured in. (see: Alternating Current; Inductor; Real Power; Reactive Power; Leading; VoltAmp (Reactive); Lagging.)

CIRCUIT - Any path through which an electric current can flow. A circuit can be made up of elements including such things as resistors, capacitors, wires, transformers, switchgear, motors, computers, etc.

CIRCUIT BREAKER - An over-current protective device, which consists of a mechanical switching device, that automatically switches off when the current exceeds a certain ampere value for a certain duration. Circuit breakers can be designed to have a long or short trip time depending on how critical small overloads are to a circuit. The trip time on a direct short circuit is almost instantaneous. Circuit breakers have an ampere trip rating for normal overload protection and a maximum magnetic ampere interrupting capacity (AIC) for short circuit protection. (see: Fuse)

COMMON MODE VOLTAGE - Electrical "noise" voltage that is measured between the neutral conductor and the system ground. This "noise" is often generated when harmonic currents in power conductors couple into close, parallel, unshielded signal conductors, creating harmonic voltages and often results in loss of data which are being shared among computers on a network. (see: Isolated Ground, Conductor, Noise, Voltage,).

CONDUCTOR - A wire, cable or bus bar designed to carry electrical current as part of a circuit. (see: Circuit.)

CONTACTOR - An electro-mechanical switch that is opened and closed by turning an electromagnetic coil on or off. The coil requires only a low current to operate, (and often operates at a low voltage) and the contactor is capable of switching large currents. A high-power circuit can be controlled with a small switch and small/thing wire from a remote location. (see: Contacts.)

CONTACTS - The part of an electrical switch that actually carries the current, contacts are found in all electrical switching devices including switches, circuit breakers, and contactors. (see: Circuit Breaker; Contactor; Switch, Disconnect.)

Controller - Motor speed controller

CREST FACTOR - The ratio of the peak value of an electrical waveform to the RMS value of the waveform. The crest factor of a sinusoidal wave is the square root of two (1.414.) When a waveform is distorted the crest factor can be either higher or lower than the crest factor of a non-distorted sine wave. (see: RMS Value, Distortion, Voltage Distortion, Current Distortion.)

CRITICAL LOAD - Devices and equipment whose failure to operate satisfactorily jeopardizes the health or safety of personnel, and/or results in loss of function, financial loss, or damage to property deemed critical by the user. Sites that must operate critical loads with no failure or downtime permitted are often called "24 x 7 sites."

CURRENT - see Ampere

CURRENT DISTORTION - Any current waveform deviation from the sinusoidal waveform. When a current waveform is distorted, current harmonics are present. (see: Harmonic, Distortion, Voltage Distortion, Sine Wave)

CYCLE - The repeat time for an alternating voltage or current wave. During one cycle, a single wave is completed. A cycle can also be measured in electrical degrees, with 360Ãƒâ€šÂ° equal to one cycle. The higher the frequency of an electrical wave, the shorter the cycle. For harmonic waves, the higher the harmonic number, the shorter the cycle, or the greater the number of complete harmonic cycles in one fundamental cycle. For a "60Hz" or "60 Cycle" distribution system, one cycle lasts 1/60 of a second (16ms). (see: Alternating Current; Fundamental; Hertz; Harmonic Number; Frequency.)

CYCLING LOADS - Loads that are not on constantly, but rather, go on and off frequently, either manually or automatically.

Dc-dc -DC-DC converter, a device that converts one dc voltage to another. For instance, converting the 48V ebike battery voltage to 12V to power lights or a radio.

DC -Direct Current

DELTA CONNECTION - A method of connecting three phase transformer windings so that the three phase coils are connected end to end (eg: the end of one phase is connected to the beginning of the next phase). This configuration contains no neutral wire, and is intended for only phase-to-phase (aka line-to-line) loads. Schematically the three phase windings take the form of a triangle (or Greek letter delta) and the three phase wires are connected to the corners of the triangle. Some transformers are described as a "Delta-Delta" or "Delta-Wye" transformer, indicating that either the primary-and-secondary, or just the primary (respectively) has a Delta configuration. (see: Conductor; Neutral; Phase; Wye Connection; Transformer)

Depth of discharge - the percent of rated capacity of a battery that has been discharged from the battery.

Duty cycle - The percentage of "on time" in a circuit, 0% = off, 100% = always on. See Duty Cycle

Ebike - Electric-powered or -assisted Bicycle (abbreviated ebike or eBike).

EMF - The magnetic field formed any time current flows through a conductor.

Electrolyte - a nonmetallic conductor of electricity usually consisting of a liquid or paste in which the flow of electricity is by ions. Used in batteries.

Energy - the capacity for, or the ability to do, mechanical work. Electrical energy is measured in kilowatt-hours for billing purposes.

EV - Electric Vehicle - a vehicle where an electric motor powers the wheels.

FCV - Fuel Cell Vehicle

FET - Field effect transistors

Float charge - charging current supplied to a battery which overcomes the battery self-discharge rate. This current, under otherwise normal conditions, will maintain the battery in a fully charged state.

Flooded batteries - Batteries that use a free-flowing liquid electrolyte, like a common automobile battery.

Freehub (cogset): A type of bicycle hub that incorporates a ratcheting mechanism, and the name freehub is a registered trademark of Shimano. A set of sprockets (called a cassette) are mounted onto a splined shaft of the freehub to engage the chain. The ratcheting mechanism is a part of the hub, in contrast to a freewheel, an older technology, which contains both the sprockets and a ratcheting mechanism in a single unit separate from the hub. In many high-end and midrange bicycles, freehubs have replaced freewheel systems. (from Wikipedia)

Freewheel (clutching): 1. Also called an overrunning clutch, it is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. 2. The condition of a driven shaft spinning faster than its driveshaft exists in most bicycles when the rider holds his or her feet still, no longer pushing the pedals. In a fixed-gear bicycle, without a freewheel, the rear wheel would drive the pedals around. (from Wikipedia)

Freewheel (cogset): Also known as a block or cluster, it consists of the rear set of sprockets and a ratcheting mechanism in a single assembly that mounts on a threaded hub. Traditional rear hubs have a standardized right-hand thread (1.375 x 24 TPI) onto which a standard freewheel is screwed. (from Wikipedia)

Freewheeling Speed: The speed at which the hub motor and wheel will spin (whether kmh or mph) without having contact with the ground; literally “free wheel". Also called "unloaded top speed"

Frequency - the number of complete alternations or cycles per second of an alternating current. It is measured in Hertz. The standard frequency in the US is 60 Hz. However, in some other countries the standard is 50 Hz.

FULL LOAD CURRENT - The greatest current that a distribution system or part of such a system is designed to carry. For motors or other device the full load current is the current used by the device when it is operating at its maximum rating. Any current in excess of the full load current is considered an overload.

FUNDAMENTAL (COMPONENT) - Voltage or current at the planned frequency for a distribution system. In the United States the fundamental is usually 60 Hz. In many European countries the fundamental is 50 Hz, and in some aircraft systems a fundamental of 400 Hz is used. When discussing harmonics the fundamental component is the 1st harmonic, or has a harmonic number equal to one (1.) (see: Frequency; Harmonic Number; Hertz)

FUSE - An over-current protective device, which consists of a conductor, that melts and opens the circuit when the current exceeds a certain ampere value for a certain duration. Fuses can be designed to have a long or short trip time depending on how critical small overloads are to a circuit. The trip time on a direct short circuit is almost instantaneous. Current limiting fuses are designed to trip very rapidly and to limit the energy in a short circuit to a small value, thus preventing a possible electrical explosion. (see also: Circuit Breaker.)

Ga. - American Wire Gauge - see AWG above

Gassing - Gas by-products produced by the chemical reactions that occur when charging a battery. Since one of these gasses is often hydrogen, safety precautions must be taken to ensure proper ventilation to avoid the danger of explosion.

Grid - in the electrical arena, a term used to refer to the electrical utility distribution network.

Ground - a conducting connection between an electrical circuit or device and the earth. A ground may be intentional, such as in the case of a safety ground, or accidental which may result in high overcurrents.

H1, H2, H3 - The names given to the three phase primary (input) terminals of a transformer. (see: Delta Connection; Wye Connection; X1, X2, X3.)

HARMONIC (COMPONENT) -An integral multiple of the fundamental frequency. A distorted waveform can be broken down into a series of harmonic components using equations developed by Fourier. The distorted waveform can be thought of as being composed of sinusoidal harmonic components, each component having a particular amplitude and phase relationship to the fundamental. (see: Amplitude; Distortion; Phase Relationship.)

Hall -Hall effect sensor, hall effect throttle - A device that produces an electrical signal based on the strength of a magnetic field.

Heatsink - A big chunk of aluminum or copper with cooling fins.

HARMONIC DISTORTION - Periodic distortion of the sine wave. See Distortion and Total Harmonic Distortion (THD).

HARMONIC FILTER - A device for removing harmonic currents that are flowing in a power distribution system. Harmonic filters can be passive in operation, in which case they absorb harmonics using a tuned electrical circuit comprised of capacitors, resistors, and inductors, or they can be active in operation in which case they remove harmonics electronically. (see: Harmonic Suppression System.)

HARMONIC NUMBER - The integral number given by the ratio of the frequency of a harmonic to the fundamental frequency. EG: for a frequency of 180 Hz, the harmonic number is "3" (180/60) or the "3rd harmonic".

HARMONIC RESONANCE - A condition in which a three-phase power distribution system becomes tuned to one of the harmonic frequencies. When such tuning occurs, huge amounts of harmonic current circulate within the system. If this condition persists for any length of time, the entire system can be destroyed by fire or explosion. This is a very dangerous situation that is usually found when an attempt is made to add capacitors to a 3-phase distribution system that is already carrying small amounts of harmonic currents.

HARMONIC SUPPRESSION SYSTEM - A device used to render a distribution system free of harmonic currents by preventing the formation of these currents. A harmonic suppression system differs from a harmonic filter in the way it deals with harmonic currents. Instead of removing harmonic currents after they are circulating in the distribution system (treatment) the suppression system keeps them from ever existing in the system (prevention.) Harmonic suppression systems are totally passive in their operation. (see: Harmonic Filter.)

HERTZ (Hz) - A unit used to express frequency. It is named in honor of Hertz who did pioneering work measuring the frequency of audio waves. This term is preferable to "cycles per second (and is easier to say.) 1 Hz = 1 cycle per second. (see: Cycle; Frequency.)

HP - Horsepower - a measure of power (power is energy per time). For engines this is torque multiplied by rotational speed. In the automotive world, it is used to rate engines, but comparisons based on engine horsepower can be misleading because torque varies significantly with RPM for an ICE and the test conditions of the measurement must be carefully specified (e.g. SAE test procedures). In contrast, for electric motors, horsepower is simply defined as 746 Watts (0.746KW).

HVC - High Voltage Cutoff; a parameter applicable to programming the controller chip. HVC is used during charging and regeneration of the battery pack. In use, once the battery pack reaches the HVC limit any additional voltage above is shunted to waste heat.

Hz - Hertz - cycles per second, a measure of AC frequency. The U.S. AC electric grid is 60Hz.

ICE - Internal Combustion Engine - An engine that burns fuel inside a reaction chamber to create pressure inside the chamber that is converted into rotary motion. ICE engines are typically based on the Otto cycle, Atkinson cycle, or Wankel engine.

IMPEDANCE - The AC circuit equivalent of resistance in DC circuits. Impedance is the opposition to AC current flow made up of the available circuit elements of resistance, capacitive reactance, and inductive reactance. Each AC current frequency (harmonic) may be subject to a different impedance in the circuit.

INCOMING POWER - Electrical power being supplied either by a public utility or by self-generation.

INDUCTIVE LOAD - A load that draws AC power through a magnetic coil. Examples include AC motors, lighting ballasts, and transformers. (see: Alternating Current; Capacitor; Inductor.)

INDUCTOR - Also called a reactor or line reactor. A device that stores electrical current as a magnetic field. Inductors resist a change in current. Inductors are used to create system impedance by resisting a sudden change in current with the magnetic field. The unit used to measure inductors is "henry." A henry, abbreviated "H", is a very large value, so the more common unit is "milli" (0.001 H) or mH. (see: Capacitor; Inductive Load; Magnetic Field; Real Power; Reactive Power; Leading; Lagging.)

IN PHASE - A term used to describe the angular relationship between two or more waveforms. When the waveforms are in phase, the starting points of the various waveforms are at the same point in time and are not separated by any electrical degrees. (see: Out of Phase.)

IN-RUSH CURRENT - The maximum current drawn by a transformer when it is first energized or by a motor during the starting period. The inrush current on a transformer consists both of the current necessary to power connected loads and the current necessary to first magnetize the transformer windings. (see: Current; Transformer)

INTERRUPTION, MOMENTARY - A type of short duration variation. The complete loss of voltage on one or more phase conductors for a time period between 30 cycles (0.5 seconds) and 3 seconds. (see: Voltage; Cycle; Conductor)

INTERRUPTION, SUSTAINED - Any interruption not classified as a momentary interruption. A type of long duration variation. The complete loss of voltage on one of more phase conductors for a time greater than 1 minute. (see: Interruption, Momentary)

INVERTER - A device that converts DC power to AC power. Term "inverter" is sometimes used interchangeably with "Variable Frequency Drive" or "VFD". (see: AC Power; DC Power; Adjustable Speed Drive; Rectifier; Variable Frequency Drive)

ISOLATED GROUND - An extra insulated equipment grounding conductor run in the same conduit or raceway as the supply conductors and separate from the normal equipment grounding conductor. This conductor is insulated from the metallic raceway and all ground points from its origin at the grounding point in the main entrance to its termination at a special isolated ground-type receptacle. The theory is that by grounding sensitive electronic equipment with a separate isolated grounding wire, noise caused by currents flowing on the normal grounding system will not affect the sensitive equipment. There is no firm evidence that this extra isolated ground wire contributes substantially to better equipment operation. (see: Common Mode Voltage; Ground; Noise; Isolation; Main Entrance.)

ISOLATION - Separation of one section of a system from undesired influences of other sections. Isolated grounds, circuit breakers, and transformers are three very different examples of isolation.

Inverter - an electrical device which is designed to convert direct current into alternating current.

kV: Kilovolts; 1000 volts.

Kv: Also denoted as KV, is the measurement of RPMs per volt as used in reference to the rotational speed of brushless motors.

KW - kilowatt - unit of power equal to 1000 watts. Abbreviated kW or KW.

KWh - kilowatt-hour - unit of energy or work equal to one kilowatt for one hour. See watt-hour

Joule - a unit of work or energy equal to one watt for one second. One kilowatt hour equals 3,600,000 Joules.

LAGGING - A term used to describe the relationship between voltage and current sine waves for a device being powered by an AC supply. When the current waveform starts later than the voltage waveform the current is said to be lagging. Induction motors have lagging currents. (see: Leading; Displacement Power Factor.)

LBS - Local Bicycle Shop

LEADING - A term used to describe the relationship between voltage and current sine waves for a device being powered by an AC supply. When the current waveform starts earlier than the voltage waveform the current is said to be leading. Capacitors have leading currents. (see: Lagging; Displacement Power Factor.)

Li-Ion - Lithium Ion- a battery technology.

LiFeP04 - Lithium Iron Phosphate battery - These kind are very fire resistant

LiPo - Lithium-ion polymer batteries, polymer lithium ion, or more commonly lithium polymer batteries (abbreviated Li-poly, Li-Pol, LiPo, LIP, PLI or LiP) are rechargeable batteries (secondary cell batteries).

LINE LOSS - The power lost when a current passes through the resistance of the wires of an electrical distribution system from the source to the load. This power is given in watts and is calculated using the formula: Line loss = I2R. To keep this loss at a minimum large wires are used to reduce the resistance. High harmonic currents increase line loss due to the large I2 factor, which is why it is important, in order to save power, to reduce harmonic current flow in a distribution system. (see: Ampere; Resistance)

LINEAR LOAD - Electrical load which draws current continuously or whose current waveform is the same as the voltage waveform supplying the load. Systems with all linear loads do not have harmonic currents in the electrical distribution system. Linear loads typically draw sinusoidal current and voltage waveforms. Examples of linear loads include motors, incandescent lights, and heaters. (see: Nonlinear)

LOAD - Any piece of equipment that uses electricity to power it. Examples are motors, computers, etc. Also the name for the conductor between a distribution device (transformer, disconnect, drive) and a piece of equipment. Usage: the "load side" of the transformer is also the side where the load is connected, and is opposite the "line side" of the transformer. (see: Line; Transformer; Distribution System)

LOAD BALANCE (OR LOAD IMBALANCE/UNBALANCE) - In a 3-phase Wye electrical distribution system powering loads connected phase-to-neutral, load balance refers to how closely the currents flowing in each of the phases are equal. To reduce neutral currents it is important to keep the phase loads as closely balanced as possible. (see: Wye; Current; Neutral; Voltage Imbalance)

LONG DURATION VARIATION - A variation of the RMS value of the voltage from nominal voltage for a time greater than one minute. Usually further described using a modifier indicating the magnitude of a voltage variation (see: Undervoltage; Overvoltage; Voltage Interruption).

LVC - Low Voltage Cutoff; a parameter applicable to programming the controller chip. LVC is typically set close to the manufacturer's recommended low voltage limit for the specific battery chemistry. In use, LVC determines when the controller sets the throttle signal to zero, effectively cutting off acceleration and protecting the battery from further discharge and/or potential damage.

LYCRA - In the ebike community the more concise & technical term for the 'big athletic type' that ride bicycles are known as Lycras. And it has nothing to do with what they wear but rather an attitude of smug superiority.

MAGNETIC FIELD (EMF) - The magnetic field formed any time current flows through a conductor.

NEV - Neighborhood Electric Vehicle

NiCd - nickel-cadmium battery; (abbreviated as NiCd or NiCad) - nickel-cadmium battery

NiMH - Nickel Metal Hydride- a battery technology.

NOISE - Unwanted electrical signals occurring in an electrical distribution system, which can produce undesirable effects in the circuits of equipment powered by the system.

NONLINEAR LOAD - Electrical load which draws current discontinuously or whose current waveform is different from the voltage waveform supplying the load. Systems with some or all nonlinear loads have harmonic currents in the electrical distribution system. Nonlinear loads typically draw distorted current and/or voltage waveforms. Examples of nonlinear loads include variable frequency drives, computers, fluorescent lighting. (see: Variable Frequency Drives; Distortion; Linear)

NORMAL MODE NOISE - Electrical "noise" voltage that is measured between or among the phase conductors in a 3-phase Wye distribution system. (see: Noise; Common Mode Voltage; Phase; Voltage; Conductor; Wye)

Ohm - a unit of electrical resistance. A circuit resistance of one ohm will pass a current of one ampere with a potential difference of one volt. See Ohm's Law

OHM - Unit of electrical resistance. One volt will cause a current of one ampere to flow through a resistance of one ohm. Ohm is represented by the Greek letter for omega: "W." (see: Resistance)

OHM'S LAW - Credited to the German scientist Georg Ohm. The relationship between voltage, current and resistance in an electrical circuit. The law states that R = V / I. (The resistance-R equals voltage-V divided by current-I.) If any two of the parameters are known for a circuit, the third can be calculated using Ohm's Law. (see: Voltage; Ampere; Ohm; Resistance)

OHMMETER - A meter for directly measuring electrical resistance expressed in ohms. (see: Ohm; Resistance)

ON LINE - A term used to designate that a connected electrical load is powered up and operating. In the case of a UPS, an on line device powers the load from batteries at all times, and the batteries are continuously charged by the line. When incoming power disappears there is no switching since the batteries are already powering the load. (see: Off Line; Incoming Power; Load; UPS.)

OUT OF PHASE - A term used to describe the angular relationship between two or more waveforms. When the waveforms are out of phase, the starting points of the various waveforms are at different points in time and are separated by some number of electrical degrees. (see: In Phase; Leading; Lagging)

PASSIVE FILTER - A filter containing no active or electronic components. Usually constructed with inductors, capacitors, and resistors. (see: Harmonic Filter; Shunt Filter)

PbA - Lead Acid- a battery technology.

Peukert's Law (Peukert Effect) - estimates the capacity of an electric battery over a range of discharge rates. See Wikipedia Peukert's law for more information. Basically, the faster you discharge a lead-acid battery, the less capacity it has.

PEV - Personal Electric Vehicle

PHASE (THREE PHASE CIRCUIT) - One of the three line or load connection points on a transformer or the wire connected to that point. In a 3-phase transformer the sinusoidal voltage waves are out of phase with each other by exactly 120 electrical degrees.

PHASE SHIFT - The displacement in time or in electrical degrees of one sinusoidal waveform relative to other sinusoidal waveform(s). (see: In Phase; Out Of Phase; Leading; Lagging)

PHEV - Plug In Hybrid Electric Vehicle

Pot - potentiometer, a variable resistor. Also a medicinal-herb used to adjust attitude.

Power - the rate at which work is performed or that energy is transferred. Electric power is commonly measured in watts or kilowatts. A power of 746 watts is equivalent to 1 horsepower.

POWER CONDITIONER - Any device which helps to improve the quality of incoming power by carrying out one or more functions, such as reducing spikes and surges, lightening arrestor, removing harmonics, balancing loads, correcting power factor, etc. (see: Spike; Sag; Surge; Incoming Power; Harmonics; Load Balance; Power Factor)

POWER FACTOR (TRUE OR TOTAL POWER FACTOR) - This is the ratio of real power to apparent power being supplied to any electrical load, linear or non-linear. Another way to describe power factor is: the ratio of the power that actually does useful work to the power that must be supplied to get the work done. If all the power supplied does useful work, the ratio is one (1) and the power factor is unity. (Power Factor (true) equals the real power, which is delivered at 60 Hz, divided by rms apparent power, or FPTrue = kW60 Hz / kVArms) Power factor ranges from zero (no useful work done) to unity. Resistive loads such as heaters have a unity power factor. When non-linear loads are being powered and harmonic currents are flowing in the system, true power factor is always lower than displacement power factor. (see: Linear Load; Nonlinear Load; Displacement Power Factor; rms)

PV - Photovoltaic

PWM - Pulse Width Modulation

REACTIVE POWER - The power delivered that does no useful work, but must be present so that the work can be done. Example: the Apparent Power necessary to turn a motor at a specific speed and torque consists of the Real Power (contributes to speed and torque) and the Reactive power (energizes the motor coil, but does not contribute to speed or torque. The Reactive power is measured in volt amps-reactive, or kilo-volt amps-reactive; abbreviated "VAR" or "kVAR". (see: Apparent Power; Real Power; Volt Amp Reactive)

RECTIFIER - A device that converts AC power to DC power. A rectifier may include SCRs, Diodes, or IGBTs for rectification. Only Diodes are passive non-controlled devices. (see: Inverter; SCR)

REAL POWER - The component of apparent power delivered that is useful and actually does the work. It flows from source to load and is totally used by the load. Example: the Apparent Power necessary to turn a motor at a specific speed and torque consists of the Real Power (contributes to speed and torque) and the Reactive power (energizes the motor coil, but does not contribute to speed or torque. Real power is calculated by multiplying current times voltage times true power factor. (Pwatts = I x V x FPtrue) Power losses in wires can be calculated by squaring the rms current and multiplying by the resistance. (Pwatts = I2rms x R). Real Power is measured in watts, or kilowatts; abbreviated "W" or "kW". (see: Volt Amp; Current; Power Factor; Apparent Power; Ohm's Law; Reactive Power; Watt)

REGEN - Regenerative braking: using a motor's ability to act as a generator, to slow the EV and supply the batteries with replacement power.

RESISTANCE - The non-reactive opposition, which a device or material offers, to the flow of direct, or alternating current. Measured in ohms. Given the symbol R for resistance or, sometimes in AC circuits, Z for impedance. Can be compared analogously to the size of a pipe in a water system. (see: Current; Voltage; Ohm's Law; Ohm; Reactive power)

RMS - In mathematics, the root mean square (abbreviated RMS or rms), also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids. RMS is used in various fields, including electrical engineering; one of the more prominent uses of RMS is in the field of signal amplifiers. (from Wikipedia)

RPM - Revolutions Per Minute

SAG - A lowering of voltage, common with battery supplied power. (See Peukert's Law)

SHIELD - As normally applied to instrumentation cables, refers to a conductive sheath (usually metallic) applied, over the insulation of a conductor or conductors, for the purpose of reducing the induction of electrical noise from one wire to another. The shield is usually grounded so that unwanted currents are transferred to the grounding system, rather than to the wires in the circuit. (see: Conductor; Current; Ground)

SHUNT FILTER - A passive filter consisting of inductors, capacitors, and resistors designed to eliminate one or more harmonics. The most common variety is an inductor in series with a shunt capacitor. When tuned to the proper harmonic frequency and connected phase-to-phase in a 3-phase distribution system, this shunt filter absorbs harmonic currents at the point where it is connected, keeping them from flowing back to the transformer. (see: Passive Filter; Inductor; Capacitor; Resistance; Harmonic; Harmonic Filter; Phase; Current)

SINE WAVE - The normal waveform of an AC voltage or current. (see: Alternating Current)

SINGLE PHASE - A system for delivering electrical power that utilizes one phase conductor (often called the "hot" wire) with a neutral leg as a return line.

SINGLE PHASE LOAD - A load connected between a phase wire and another return wire. In the case of single-phase loads connected in a 3-phase Wye distribution system, the loads are connected between a phase wire and the common neutral return wire. (see: Split Phase, Wye Connection)

SKIN EFFECT - Skin effect is the phenomenon where the apparent resistance of a wire increases as the frequency increases. At higher frequencies a thin surface layer of the wire carries all the current. Therefore the effective wire size is smaller. To avoid problems with increased resistance at high frequencies, large wires are often replaced with bundles of many small wires. Although the cross sections of the large and multiple-small wires are the same, the small wire bundle has a much larger surface area and therefore a greater current carrying capacity.

SLA - Sealed lead-acid, see VRLA

SPIKE - (slang for surge) A large momentary increase in the amount of voltage or current supplied to or carried by a circuit.

STALL - Condition where the motor is held against rotation. Stall torque is typically the maximum torque a motor can produce at zero RPM.

STAR CONNECTION - Same as a "Y" or "Wye" connection. A type of three-phase connection is so called because, schematically, the joint of the phases looks like a "Y" in a 3-coil motor phase (9 coils, in groups of three phases), and it looks like a 5-point star in a 5-coil motor phase (15 coils, groups of 5 coils in three phases). (see also: Wye)

SURGE - A Surge is an unwanted momentary transient over voltage that may be present on an AC power circuit. A Surge may be as brief as a few billionths of a second or as long as a few thousandths of a second (millisecond). For AC power circuits, surges are a few tens of volts constitute a surge. Electronic equipment connected to a circuit that experiences a surge may become damaged. (see: Swell)

SWELL - A temporary increase in the rms value of the voltage of more than 10% the nominal voltage, at the power frequency, for durations from 0.5 cycle to one minute. (see: Cycle; Voltage, Nominal)

SWITCH - A device for making, breaking, or changing connections in a circuit. (see: Contacts)

THREE PHASE CIRCUIT - See Phase (3-phase Circuit)

THREE PHASE LOAD - A load connected phase-to-phase so that it draws power equally from all three phases at the same time. Three phase loads can be powered either by a delta configured power distribution system or to a Wye connected system. When three phase loads are powered by a Wye system, the common or neutral wire is not used. (see: Delta; Wye; Phase; Distribution System; Neutral)

Timing - Angular relationship between magnetic poles and switching point in a motor.

TOTAL HARMONIC DISTORTION (THD) - The ratio of the rms value of the harmonic currents or voltages to the value of the fundamental current or voltage. This is usually expressed as a percent of the fundamental current or voltage.

TRANSFORMER - A passive electric device consisting of multiple coupled windings, used to transfer power by electromagnetic induction between circuits at the same frequency. A transformer can have the same input (primary) and output (secondary) voltage, in which case it is called an isolation transformer, or the output voltage can be higher than the input voltage (step-up transformer) or lower than the input voltage (step-down transformer.) Since the power supplied to the input must equal the power supplied at the output, current values will vary from primary to secondary in an inverse manner to the voltage. For instance, if a transformer is rated at 480 volts and 100 amps on the primary, at a 240 volt secondary the available current will be 200 amps. (see: Circuit; Frequency; Isolation; Volts; Amperes; OhmÃƒÂ¢Ã¢â€šÂ¬Ã¢â€žÂ¢s Law; Current)

TRIPLEN HARMONICS - A term that refers to odd multiples of the third harmonic (i.e. 3rd, 9th, 15th, 21st, etc.) In a three-phase wye connected system Triplen harmonics flowing in the phase wires are summed in the neutral so that the neutral carries more harmonic current than any of the phase wires.

VARIABLE FREQUENCY DRIVE (VFD) - A device to control the speed and efficiency of AC electric motors. The device operates by taking AC from the distribution system and rectifying it to power on a DC bus. An inverter with the capability to produce variable output frequencies then re-converts the DC to AC that powers the motor. Since the speed of an AC motor is proportional to the frequency of the AC supply, the speed can be adjusted over a wide range. (see: Adjustable Speed Drive; AC Power; DC Power; Rectifier; Inverter; SCR)

Volt - Named after the Italian engineer Alessandro Volta. The electrical potential difference or pressure across a one ohm resistance carrying a current of one ampere. One volt is originally estimated as the electrical pressure resulting from one wrap of wire through a transformer. Now more accurately known to be slightly more than that.

Voltage drop - a voltage reduction due to impedances between the power source and the load. These impedances are due to wiring and devices and are normally minimized to the extent possible.

VOLT AMP - The unit of measurement for apparent power (the total amount of power that must be delivered to a load to enable it to work.) Given the symbol VA or for large amounts, kVA.) (see: Watt; Apparent Power). Sometimes used as a power rating for an inverter which converts DC to AC.

VLRA - VRLA, Valve Regulated Lead-Acid battery

Watt - Named after the British Engineer James Watt. A unit of power equal to the rate of work represented by a current of one ampere at a potential of one volt. - see Watt

WYE CONNECTION - A method of connecting three phase transformer windings so that one end of each of the three phase coils is connected together to a common point. The other ends of the three phase windings are connected to the phase conductors. The common point is connected to a fourth line or load wire, called the "neutral" wire. With this configuration, single-phase loads can be connected from each phase wire to the neutral wire (aka phase-to-neutral, line-to-neutral).

The current in each phase wire returns to the transformer through the neutral wire. When only balanced fundamental currents are flowing in the phase wires, this configuration has the advantage that no current flows in the neutral, due to phase cancellation. If triplen harmonic currents are present in the phase wires, however, the Triplen harmonic currents do not cancel in the neutral, but are additive. Thus the neutral can carry more harmonic or rms current than any of the phase wires.

Schematically the three phase windings take the form of the letter "Y," hence the name wye connection. Some transformers are described as a "Delta-Wye" transformer, indicating that the primary side of the transformer has a Delta and the secondary has a Wye configuration. (see: Conductor; Delta Connection; Load Balance; Phase; Transformer; Neutral)

Xlyte - Crystalyte

X1, X2, X3 - The names given to the three phase secondary (output) terminals of a transformer. (see: Wye Connection; Delta Connection; H1, H2, H3)

X0 - The name given to the neutral secondary (output) terminal of a wye-connected transformer. (see: Wye Connection; X1, X2, X3; H1, H2, H3)

ZERO CROSSING - The point on an AC wave where the wave crosses the zero-amplitude line and changes sign from positive to negative or negative to positive. (see: Alternating Current)

-and yes, you have my permission to copy this and post it elsewhere as long as I get credit-

-some material sourced from http://www.harmonicslimited.com/foundations/store/storepage.asp?page=glossary (TD)