While designing an power inductance (shape of magnetic core:U ; 25KV as voltage and 22A as current) to protect capacitor banks(used as power factor correction's) from transient switching conditions (over-current ), i realized that it is very important to have B (the magnetic flux density ) as high as possible. You can play with your airgap to store more energy but there are consequences.
In fact, at the time B=Bsat, an increasing magnetic flux density lead to the decreasing of the permeability of the magnetic core. Therefore, the inductance value will decreases too since you want it to be kept constant .
At this point, i have 03 questions:
1. Which material core can be used to solve this issue, since trying to increase B sometime leads to increase losses in magnetic core too.
2. How to solve arcing issues due to capacitors banks switching which creates harmonics.
The magnetic design is similar to any other inductor, the main problem is the electric field. In this type of designs is very important the coil former (shape and material), the insulation of the cables and especially the final connections. If "N" is the total number of turns, the coil former must have different compartments so that the voltage between turns does not exceed the wire maximum voltage. If the coil former provides insulation it is not necessary to use a special cable, although special care must be taken at the distances to the core and between clays. Serial connection of small inductors using high voltage cable is another option.
Hello Aristide,
It is important to not from where the arcing is actually initiated. The source is the induced voltage in your inductor due to changes in current through the inductor. Is it possible to reduce the change in current? May an increase of the total inductance be of help?
Regarding the winding design of the inductor, as Jose already stated, the winding structure defines how much volume is necessary for the insulation. If the cable itself is able to withstand the full voltage, it costs a lot money and volume. If you know the total maximum voltage expected and the total number of turns, you can calculate the voltage drop per turn. Depending on what cable you choose you may arrange the turns such that the turns facing each other are not seeing too much voltage. As stated, the coil bobbin may have separate sections and you may use techniques as package winding.
If 25 kV is the system voltage, this can be exceeded by the inductor - depending on the capacitor and inductor value. Please simulate or calculate the possible peak current of your setup in order to get a notion about the possible peak voltage in the inductor.
Much success!
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