I

= current intensity in A

E

= empressed voltage in V

U

= voltage, terminal voltage in V

R

= resistance in w

L

= inductivity in H

w

= gyro-frequency in or Hz

f

= frequency in or Hz

C

= capacity in F

r

= resistivity in

c

= unit conductance in

A

= conductor cross-section in mm²

d

= diameter in mm

P

= power in W (active power)

Q

= reactive power in Var

S

= apparent power in VA

W

= work in Wh or Ws

cos j

= power factor

h

= efficiency

= flux in A

B

= magnetic induction in T or or

H

= magnetic field strength in

E

= electric field strength in

f

= magnetic flux in Wb or Vs

F

= force in N

v

= velocity in

w

= number of turns

t

= time in s or h

J K

= initial temperature

J W

= final temperature

R_K

= resistance at initial temperature

R_W

= resistance at final temperature

µ

= temperature coefficient in

p

= 3,14

Ohm’s Law

power

P = U₂ · I

[W]

P = I² · R

[W]

[W]

work

W = U · I · t

[V · A · s = Ws]

W = P · t

[W · s = Ws]

diameter of a conductor

[mm²]

resistance of a conductor

[W]

[W]

influence of temperature on the resistance of the conductor

R_W = R_K

[1 + µ(J₂ - J₁)]

condition: R_i1 = R_i2 = R_i3

R_E = equivalent resistance

I_G = total current intensity

Condition:

Equal power sources are connected in parallel.

E = E₁ = E₂ = E₃

for 2 resistances connected

for n equal resistances

I_G = I₁ + I₂ + I₃

flux:

magnetic flux:

magnetic resistance:

1 = magnetically effective length in m

A = flux passage area in m²

comparative figure u_r for air = 1, 000 000 4

magnetic permeability

relative permeability

m_r - comparative figure

induction constant

magnetic field strength

magnetic induction

B = m · H = m_o · m_r · H

induced voltage

[V]

self-induction

- self-inductance

[H]

[H]

- voltage of the self-induction

[V]

electric field strength

= voltage in V

= thickness of the dielectric in m

charge

Q = I · t

[A_s]

capacity

[F]

Q = quantity of electricity in A_S

C in F (1F = 1 A_S/V)

equation of dimensioning

dielectric constant

relative dielectric constant

e_r: matter constant, relative to the vacuum

absolute dielectric constant

dielectric flux density

D = e · E

frequency

T = cycle duration in s

gyro-frequency

phase angle

instantaneous value of a sinusoidal a.c. voltage

instantaneous value of a sinusoidal a.c. current

maximum value

- of a sine-wave voltage

U = virtual value

- of a sine current

I = virtual value

inductive resistance

(inductive reactance)

L in H

capacitive resistance

(capacitive reactance)

C = capacity in F

impedance

[W]

ohmic drop in voltage

U_R = I · R

[V]

inductive voltage drop

U_L = I · X_L = I · w L

[V]

capacitive voltage drop

[V]

Ohm’s law for alternating current

[A]

apparent power

S = U · I

[VA]

active power

P = U · I · cos z

[W]

reactive power

Q = U · I · sin z

[Var]

power factor

apparent power

[VA]

active power

[W]

reactive power

[Var]

power factor

efficiency for motors and generators

P_e = effective power

P_i = indicated power

speed calculation of three-phase motors rotating field speed

p = number of pole pairs

slip

[%]

n = rotor speed

[%]

[%]

[%]

[V];

[V]

[V];

[V]

[V];

[V]

J

erg

kpm

kWh

PSh

kcal

1 1

10⁷

0.102

0.278 · 10^-6

0.378 · 10^-6

0.239 · 10^-3

10⁷

1

0.102 · 10^-7

0.278 · 10^-13

0.378 · 10^-13

0.239 · 10^-10

9.81

9.81 · 10⁷

1

2.72 · 10^-6

3.70 · 10^-6

2.34 · 10^-3

3.60 · 10⁶

3.60 · 10¹³

3.67 · 10⁵

1

1.36

860

2.65 · 10⁶

2.65 · 10¹³

2.70 · 10⁵

0.7355

1

632

4187

4.19 · 10¹⁰

427

1.16 · 10^-3

1.58 · 10^-3

1

W

kW

kpm s^-1

PS

kcal s^-1

kcal h^-1

1

10^-3

0.102

1.36 · 10^-3

2.39 · 10^-4

0.86

10³

1

102

1.36

0.239

860

9.81

9.81 · 10^-3

1

0.0133

2.34 · 10^-3

8.43

735.5

0.7355

75

1

0.1757

632

4187

4.19

427

5.69

1

3600

1.16

1.16 · 10^-3

0.119

1.58 · 10^-3

2.78 · 10^-4

1