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In Reply to: Whatever happend to center tapped chokes?? posted by Bas Horneman on June 17, 2002 at 09:18:33:
As a post below says, only one half of the choke is operating at a given time.I think there will be a problem with using this arrangement as an input choke, in that the normal function of an input choke is that the magnetic field storage in the core "fills in" the gaps between the current peaks of the input, the critical inductance being the lowest value with enough energy storage to achieve this. In the centre tap arrangement this can't happen because the magnetic flux must reverse direction each half cycle, so it must fall to zero on the way through.
Follow Ups:
Hey-Hey!!!,
I've been looking at this set up since you posted questions. I think that the half of the transformer winding--CT to leg in question, must have this inductance. THe other side is carrying little if any current to contribute to magnetizing things in the core. Another concern is the DC content, a 'regular' iron cored choke has a substantiol air gap, usually the E's and I's arranged seperately and spaced with some paper. A power trans won't have this air gap and will behave more like a swing choke, high inductance until current flows. This might be a good thing...as the critical inductance increases with decreasing current, the inductance will also increase with less current. I have a 2 kV power trans I am going to experiment on, it is a big one, about 10 kg, I think that the primary should be left open or with BIG resistor actoss it, will try both ways. Any suggestions for experiment set ups?
regards,
Douglas
Hey-Hey!!!,
There is one benefit I can see with this set up. I think that the PIV ratings for the diodes will be very low. I'll walk through a cycle, with Bas' schematic. As the top of the secondary goes high it will begin conducting current, this current will drive the lower half of the choke lower than B+, as the lower secondary is going negative wrt the top one. HTis is the primary reason for this in my book, I think that best use of the 600 PIV schottky diodes can be obtained in this sort of circuit. fewest diodes( two ) and ability to use a standard CT secondary of more than 200 V per side.
good listening,
Douglas
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