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 HOME EXPLANATION ABOUT THE SYMBOLS TUTORIAL ON CREATING THE MENU'S SYMBOLS LIST DATABASE SCHEMATIC MEMENTO-1 GENERAL MEMENTO-2 CABLES MEMENTO-3 MOTORS MEMENTO-4 FORMULA MEMENTO-5 BELGIAN ELECTRICAL INSTALLATION NORM LINKS PRIVATE - NO ACCESS

### Memento - 4    Electric formula

Electric formula

Voltage drop in direct current with known power value : u = 2.L.P / (S.U) [V] u = Voltage drop $\frac{}{}$ [V]

U = Voltage [V]

I = Current strength [A]

P = Power [W]

L = Length of cable [m]

S = Cross section of wire [mm²]

Voltage drop in direct current with known Current strength : u = 2.L.I / S $\frac{}{}$ [V]

Alternative current monophase u =2.L.r.(I.cos f) / U $\frac{}{}$ [V]

Alternative current triphase u = (3)½.L.r.(I.cos f) / U $\frac{}{}$ [V]

Magnetic field produced by a coil of n windings with a current strength I H = n.I / L $\frac{}{}$ [A/m]

n = Number of windings

I = Current strength [A]

L = Length [m]

Magnetic induction B = µor.H [T]

µo= 4.p.10-7

µr= Magnetic relative permeability of the material

magnetic flux quantum f = B.S.cos a [Wb]

B = Magnetic induction [T]

S = Area [m²]

a = Angle between B and S

Electromagnetic force F = B.I.L.sin a [N]

B = Magnetic induction [T]

I = Current strength [A]

L = Length [m]

a = Angle between B and the conductor

Dynamic force between 2 // conductors F = 0,2.I1.I2.d.e [N]

I1 = Current strength of conductor 1 [A]

I2 = Current strength of conductor 2 [A]

d = Distance where the 2 conductors are // [m]

e = Spacing between the 2 conductors [m]

p = 3.1415

f = Frequency [Hz]

Frequency f = 1 / T [Hz] T = Period [s]
Voltage drop U = R.I $\frac{}{}$ [V]

R = Resistance of the conductor [W]

I = Current strength [A]

Resistance R = r . L / S [W]

r = Resistivity of the conductor [W.m]

r of cooper at 20°C = 17,24 10-6 [W.m]

L = Length [m]

S = Cross section of the conductor [m²]

Active Power in triphase S = 1,732.U.I $\frac{}{}$ [VA]
Active Power in triphase P = 1,732.U.I.cos f $\frac{}{}$ [W]
Reactive Power in triphase Q = 1,732.U.I.sin f $\frac{}{}$ [VAr]
Relation between powers S2 = P2 + Q2 $\frac{}{}$ [VA]

Moment

M = ML+Ma $\frac{}{}$ [Nm]

M = ML+(p/30).J.(Dn/ta) $\frac{}{}$ [Nm]

M = Motor moment [Nm]

Ma = Acceleration moment [Nm]

J = Global mass moment inertia [kg m²]

Dn = Differentiel speed [m-1]

P = Motor power [kW]

Pa = Acceleration power [kW]

ta = Time of acceleration necessary to go up of the differential speed [s]

Acceleration moment

Ma = (p/30).J.(Dn/ta) $\frac{}{}$ [Nm]

Ma = (0,105).J.(Dn/ta) $\frac{}{}$ [Nm]

Work - Energy

W = (p2/1800).J.(Dn2).M / (M-ML) $\frac{}{}$ [Nm]

W = J.(Dn2).M / (182,4.(M-ML)) $\frac{}{}$ [Nm]

Total power P = PL+Pa $\frac{}{}$ [Nm]
Acceleration time

ta = (p/30).J.Dn/(M-ML) $\frac{}{}$ [s]

ta = 0,105.J.Dn/(M-ML) $\frac{}{}$ [s]

ta = p2.J.Dn2/(9.105.(P-PL)) $\frac{}{}$ [s]

ta = J.Dn2/(9,12.104.(P-PL)) $\frac{}{}$ [s]

Impedance Z = U / I [W]
Impedance of a winding

Z = L.2.p.f [W]

Z = L.314,16 [W] at 50Hz

Impedance of a capacity

Z = 1 / (C.2.p.f) [W]

Z = 1 / (C.314,16) [W] at 50Hz

Synchronizing speed of an asynchrone triphase motor

ns = 2.60.f / p [r/min]

f = Frequency [Hz]

p = Numbre of pole per phase

 ns ( at 50Hz) p 1500 4 1000 6 750 8 375 16 250 24

Power

1 HP = 0,73549 kW = 0,74 kW

1 kcal/h = 1,163 W = 1,16 W

1 kcal/h = 4,1868 kJ/h = 4,2 kJ/h

Energy 1 kcal = 4,1868 kJ = 4,2 kJ