Uk - calculation of a choke’s voltage drop
The voltage drop of a smoothing coil and thus the voltage reduction of the connected load at the output can be determined as following. The inductive or reactive reactance (XL) dof the smoothing choke can be calculated with the inductance of the choke (L) and the mains frquency (fmains):
XL = ω x L = 2Pi x fmains x L
The voltage drop (Uk) of the smoothing choke can be calculated with the rated current (IN) and the inductive reactance of the choke (XL)
for 1-phase smoothing coils: Uk = IN x XL
for 3-phase smoothing coils: Uk = IN x XL √3
Calculation of the voltage drop (Uk) of an one-phase smoothing coil with an inductance of L = 0,3 mH, a current of I = 100 A and a rated voltage of 230 V at f = 50 Hz:
Reactance: XL = ω x L = 2Pi x 50 Hz x 0,3 mH = 0,094 Ω
Voltage drop: Uk = IN x XL = 100 A x 0,094 Ω = 9,4 V
or given as percentage to mains voltage: Uk% = Uk / Umains = 9,4 / 230 = 4%
In an american net with U = 110 V and f = 60 Hz the choke acts as following:
Reactance: XL = ω x L = 2Pi x 60 Hz x 0,3 mH = 0,113 Ω
Voltage drop: Uk = IN x XL = 100 A x 0,113 Ω = 11,3 V
or given as percentage to mains voltage: Uk% = Uk / Umains = 11,3 / 110 = 10,2%
This means the same choke will have more than twice the Uk%, if operated in an american net.
Tauscher chokes are calculated to have a small Uk%. Especially cut cores and cores made of amorphous and nanocrystalline materials have a small Uk% and thus low losses and a very good attenuation of harmonics.