operating cell temperatureNorton theoremimpressed current source theoremNRELNational Renewable Energy Laboratory
O
ocopen circuitOPoperationalORCorganic Rankine cycleoutoutputωangular frequency or angular velocityωangular frequency or angular velocity at resonance, undamped natural angular frequency, center frequencyωmmechanical angular velocityreference/nominal/rated (*) value of mechanical (m) angular velocityωHIupper (HI) break or cutoff frequency, half‐power angular frequencyωLOlower (LO) break or cutoff frequencyωLO, ωHIhalf‐power frequenciesΩunit for ohmsωLloadreactance due to load inductanceωLload1reactance due to load 1 inductanceωLload2reactance due to load 2 inductanceωMmutual reactance due to coupling of two windingsωL1self‐reactance of winding 1ωL2self‐reactance of winding 2reactance due to load impedance referred to primary side per phase reactance of delta‐connected first loadper phase reactance of delta‐connected second loadper phase reactance of Y‐connected first loadper phase reactance of Y‐connected second loadωLlsleakage reactance of secondary windingωLls ′leakage reactance of secondary winding referred to primary side of transformerper phase reactance of delta‐connected loadωLlpleakage reactance of primary windingωLmreactance of magnetizing/cross‐branch of transformerωLlineper phase reactance of distribution/transmission lineωm(t)time‐dependent mechanical angular velocity
P
ppole, peak, parallel, primaryPperformance, phosphorous, proportional control, average or real power, proportionalpoles of transfer function G(jω) from 1, …, nPDproportional–differentialPIproportional–integralPIDproportional–integral–differentialP1input real powerP2output real powerPFpower factorp(t)instantaneous powerPratrated real output powerPactualactual real output powerpin(t)input power as a function of timepout(t)output power as a function of timePininput real powerPoutoutput real powercopper loss of primary windingcopper loss of secondary windingPfeiron‐core lossPCCpoint of common couplingphphasePLLphase‐lock loopperperiodPFdisplacement or fundamental power factorPEMproton exchange membranePEMFCproton exchange membrane fuel cellpico10−12phasermsphase (phase) root‐mean‐square (rms) valuePMpermanent magnetPMGpermanent‐magnet generatorPMMpermanent‐magnet machinepnpositive and negative typesppmparts per millionPSPICEPersonal Simulation Program with Integrated Circuit Emphasispuper unitPVphotovoltaicspwpulse widthpw/perpulse width per periodPWMpulse‐width‐modulatedposcillation(t)oscillating powerπpi, or 3.141 59…
Q
Qelectric charge, imaginary or reactive powerQ = 1/(ωRC) = 1/BW = = = quality factorqquadratureq(t)electric charge as a function of timequadrantone‐quarter area of complex/Gaussian plane
R
rrotorRradius, resistanceRaarmature resistance of DC machineRCresistor–capacitor networkℜreluctance, magnetic resistanceRccore‐loss resistance, resistance of iron coreRgresistance of air gap of iron coreℜgreluctance or magnetic resistance of air gap of iron coreℜcreluctance or magnetic resistance of iron coreRpresistance of primary windingRsresistance of secondary windingsecondary resistance referred to primary side of transformerRcloss (series) resistance of capacitorR1resistance of primary winding 1R2resistance of secondary winding 2Rlineper phase resistance of distribution/transmission lineRLCresistor–inductor–capacitor networkradradiansratratedReindicates real part of a complex numberRloadload resistanceRload1resistance of load 1Rload2resistance of load 2per phase resistance of delta‐connected loadper phase resistance of delta‐connected first loadper phase resistance of delta second connected loadper phase resistance of Y‐connected first loadper phase resistance of Y‐connected second loadRHSright‐hand siderinradius inside of round wireroutradius outside of round wirermsroot‐mean‐squarermsloadsubscript for root‐mean‐square value of a load quantity (e.g. voltage)rmssourceindicates root‐mean‐square value of a source quantity (e.g. voltage)rpmrevolutions per minuterpsrevolutions per second(R − jX)complex conjugate of (R + jX)(r, Φ, z)r coordinate, Φ coordinate, z coordinate
S
ssource, stator, synchronous, slip, unit of second, abbreviation symbol for first derivative , secondary, abbreviation for jω =s, seconds 2abbreviation symbol for second derivativeSsouth (pole), surface, source terminalS = apparent power, magnitude of complex powercomplex powers1, s2two roots of characteristic equationscshort circuitcomplex output powerSratrated apparent powerSactualactual apparent powerSEERseasonal energy efficiency ratioSCRsilicon‐controlled rectifierSISystème International d’Unités (French for International System of Units)SisiliconSiCsilicon carbidesinglesingle‐phase valueSMsynchronous machineSOFCsolid oxide fuel cellSSsteady statestartstartingSMsynchronous motor/machineSTCStandard Test ConditionSTEMscience, technology, engineering, and mathematicssubsubstationSUMsummationsyssystemSWMStadtwerke Münchenswitchmechanical or electronic switch
T
tturn, time variableTunit of Tesla, period length/duration, time constant, transformer, absolute temperaturetorque in vector notationT(t)time‐dependent torquetddelay timeTeelectric torqueTcmechanical torque due to Coulomb (c) friction Tsmechanical torque due to standstill (s)TLmechanical load torqueTmmechanical torque performing useful workTGVTrain à Grande Vitesse (French high‐speed trains)ththeoreticalTHthyristor, Thévenin (TH)transtransresistanceThévenin theoremimpressed voltage source theoremTHDitotal harmonic distortion of currentTHDvtotal harmonic distortion of voltagethreethree‐phase valueτtime constant, time constant RCτptime constant for peak rectificationτRCtime constant for RC circuitτRLtime constant for RL circuitθphase shift of a time function, power factor angleθvphase shift of a voltage v(t)θiphase shift of a current i(t)θmmechanical displacement angleθnphase shift of Fourier componentθpphase shift angle between
