Electronic Transformers and Circuits is a free introductory textbook on transformers and related circuits. See the editorial for more information....

List of Symbols

Page numbers are those on which the corresponding symbol first appears. A symbol formed from one of the tabulated letters, with a subscript or prime added, is not listed unless it is frequently and prominently used in the book. Sometimes the same symbol denotes more than one property; the meaning is then determined by the context. Units are given wherever symbols are used. Small letters indicate instantaneous or varying electrical quantities, and capital letters indicate steady, effective, or scalar values.

a Coil radius
a Coil winding height
a N2/N1
A Area
Ac Core area
An Ripple amplitude
b Winding traverse
B Xc/R1 at frequency fr
B Core flux density
Bm, Bmax Maximum operating flux density
Br Residual flux density
c Insulation thickness
c Specific heat
C Capacitance
C1, Cp Primary capacitance
C2, Cs Secondary capacitance
Ce Effective capacitance
Cg Capacitance of winding to ground
Cw Capacitance across winding
d Core tongue width
d Toroid diameter
D Winding height
D Xc/R2 at frequency fr
e Voltage (instantaneous value)
eg Alternating grid voltage
ep Alternating plate voltage
E Emissivity
E Voltage (effective value)
EB Plate voltage
E0 Output voltage
E1 Primary voltage
E2 Secondary voltage
ES Secondary no-load voltage
EL Secondary full-load voltage
Epk Peak value of alternating voltage
Edc D-c voltage
Ea Voltage at top of pulse
f Frequency
fm Midband frequency
fr Resonance frequency
fc Cut-off frequency
f( ) Function of
F Factor
gm Mutual conductance
G Gap loss constant
H Magnetizing force
Hc Coercive force
i Current (instantaneous value)
I, |I|, Irms Current (effective value)
Idc Direct component of current
Ipk Peak value of current
Iav Average value of current
Ip, Ib Plate current (d-c)
IL Load current
IE Loss component of exciting current
IM Magnetizing current
IN Exciting current
IG Grid current (d-c)
j sqrt(-1) (vector operator)
J Low-frequency permeability/pulse permeability
k Thermal conductivity
k Coefficient of coupling
k 1/2 ratio of impedance/circuit resistance = sqrt(L/C)/2R
K Constant
lc Mean length of core (or magnetic path)
lg Air gap
L Inductance
Le Open-circuit inductance (OCL).
Ls Short-circuit inductance
Lm Mutual inductance
m Decrement
m Order of harmonic
M Modulation factor
MT Mean turn length
n Number (e.g., of anodes)
N Turns
N1 Primary turns
N2 Secondary turns
NL Number of layers (of wire in coil)
OCL Open-circuit inductance
p Density
p Ratio of voltages (in autotransformer)
p Rectifier ripple frequency/line frequency (number of phases)
Pa Volt-amperes per pound
Pc Core loss
PA Ripple amplitude/Edc (in rectifier)
PR Ripple amplitude/Edc (across load)
PFN Pulse forming network
PRF Pulse repetition frequency
Q ωL/R = coil reactance/coil a-c resistance
r Radius
re Equivalent radius
rp Plate resistance
R Resistance
R1 Source resistance
R2 Load resistance
RL Load resistance
Re Equivalent core-loss (shunt) resistance
S Secondary winding
S Core window width
t Time (independent variable)
t Thickness of insulation
T Period of a wave
T 2πsqrt(LsC2) (undamped period of oscillatory wave)
V Commutation voltage
V Volume (of core)
w Core-stacking dimension
Wg Gap loss
We Core loss
Ws copper loss
X Reactance
XN Open-circuit reactance = 2πfLe
XC Capacitive reactance = 1/(2πfC)
XI Inductive reactance = 2πfL
Z Impedance
ZG Source impedance
ZL, Load impedance
Z0 Characteristic impedance
α Amplifier gain
α sqrt(CgCw)
α Damping factor
ω Feedback constant
ω Natural angular frequency
δ Small interval of time
Δ Increment (e.g., of flux)
Δ Exciting current/load current
ε Base of natural logarithms (= 2.718)
ε Dielectric constant of insulation
η Efficiency
θ Temperature
θ Phase angle
μ Amplification factor
μ Permeability
μΔ Incremental permeability
π 3.14159
φ Phase angle
φ Flux (varying)
φmax Peak value of flux
Σ Summation (of a series of elements)
τ Pulse duration
ω 2πf (angular frequency)

Last Update: 2011-02-17