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Single Phase, 25mH Common Mode Choke
in 50Hz net for suppressing up to 50kHz current harmonics

 

Description

This choke has 2 windings. Through these windings flow 2 currents:

– the load current I I and
– the capacitive, common mode current, Ic=(Ic1+Ic2)/2 <<I

The total ampere turns of the current I in the core window are equal 0 and the core is not magnetized by this current. The line voltages drive the core magnetizing ampere turns 2*W*Ic, where W are the turns only of one winding ..,.
In order to use the Small Chokes Program, you need to know:
1. The inductance L of both in series connected windings W at the peak current value Ic=(Ic1+Ic2)/2. Note that the role of the inductance L is to limit the current Ic.

If L1w is prescribed the inductance of the winding W, then L >= 4*L1w .
2. The current I with all harmonics s and the frequency of its 1. harmonic
3. Ic = (IcI+ Ic2)/2 and its max. frequency. For the frequency range over 10kHz you have to use powder or ferrite core material. Due to the fact that this core material have very low permeability, the calculated gaps can be very small.

 

Design example

Input:

– Set the inductance L=25mH of both in series connected windings at the peak value of the current Ic (Ic = =0.01 x I=0.1A, 50kHz

• Set the compensated harmonics of the thermal current. Note that the sign “+” marks the compensated current harmonics: I=+10A, 50Hz
• Set the other harmonics of the thermal current,t which are not compensated without the sign “+”.
• Sellect thel inductance : L-Type = 1
• Select Cu round wire: Wire = 0
• The frequency of the first harmonic is 50Hz
• Set the the temperature rise to 60°K and the criterion = 2
• Select ferrite with a good permeability.
• Select suitable core family and the gap positions