On 4/15/12 12:43 PM, Tesla wrote:
Hi IMHO the use of MWO caps and diodes arranged to have similar ratings and values as the original cct is practical and cost effective. I personally had some reservations about the chokes used in that design as not being able to maintain 7.5Hy at the currents encountered and strongly suspect the inductance of those 4 in series would be considerably less at the charging current peaks . The cheap and practical approach IMHO is to use slightly gapped MOT secondary's as inductors. I used two un-gapped MOT secondary's in series in my version. I note the diodes used in the original were 1N5403 types (1kV PIV 3A) not 1N4009 as you suggested, those diodes are rated at 25v PIV. There is a possibility that the considerably lower 0.5 amp rating of the MWO diodes could be an issue. My version used 20 1N4007's in series for the
one issue with any sort of rectifier scheme is that if there is a flashover, or you short the output, you might put a very high current transient through your diodes, cooking them.
This is particularly a problem with voltage multipliers. Short the output, and the entire capacitor stack discharges through the diodes.
Also, you need to be aware of the ringing from the inductance in the load, which might give you twice the voltage, and cook your diodes (or forward bias them with a high peak current.. a bridge feeding a capacitor, if you short it, the voltage on the cap actually oscillates, or it would if the diode bridge didn't clamp it until the diodes go open from the peak current.
I blew up a fair number of HV diode strings charging several microfarad caps to 10kV before I figured out what was going on.
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