The reverse voltage on each diode leg is approximately equal to the TOTAL
transformer peak voltage whether it is a full wave or bridge.
The diode current requirements will be the same for full wave or bridge.
However the transformer can supply twice the current safely in full wave
compared to a bridge circuit.
Note that a transformer can only safely supply the same amount of power in
either full wave or in a bridge circuit. Twice the voltage and half the
current in bridge or 1 times voltage and 1 times the current in full wave.
A bridge circuit will use a transformer with half the total voltage that a
full wave will use.
I think that the Henry amplifier uses a tuned choke circuit so the DC
voltage will be around .9 times the rms voltage. So for 3200 VDC the rms
voltage would be around 3600 volts across the transformer if it was a bridge
circuit. If it is a full wave (not a bridge) the full transformer voltage
would be 7200 volts rms. The peak voltage for the 3600 volt transformer
would be 5090 and for the 7200 volt transformer it would be 10180 peak.
Each diode legs reverse voltage ratings should be 1.5 to 2 times the peak
voltage of the transformer. For the above example each diode leg should have
a PRV of 8000 to 10000 volts for the bridge circuit or 15000 to 20000 volts
for the full wave circuit.
When using strings of diodes (1N5408) do not put resistors or capacitors
across each diode. Just string them together for the desired voltage rating.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Han Higasa
> Sent: Wednesday, January 02, 2008 3:42 AM
> To: Amps@contesting.com
> Subject: Re: [Amps] High voltage power supply for linear amp
>
> Hi Jose
>
> A single leg in a HV rectifier bridge need half PIV (Peak Inverse
> Voltage)
> and provide two times a rating current compared to a half-wave rectifier
> because a bridge has two legs against reverse vulgates and also two legs
> for
> forward current.
>
> 1N5408 has 1000V RRV (max repetitive reverse voltage) and 3A average
> forward current.
>
> 3200 V-DC mean approx. 2285 V-AC rms.
> A reverse-voltage on a leg of a diode bridge is around 1600 or 1700 V.
>
> When using 1N5408 two diodes per leg is OK, if super-high reliability
> diodes and super air-conditioner have been chosen.
>
> To avoid any failure by temperature or surge voltage choose safety
> coefficients of x2 or 3x; use four, five or six diodes per leg.
>
> If you use five 1N5408 diodes per leg, the bridge will provide
> 10 kV RRV and 6 A average forward current.
> If six then 12kV RRV and 6A.
>
> Additionally someone says modern rectifier diodes need NO parallel
> capacitors or M-ohm balance resistors -- anyone's opinion?
>
> HNY to all,
> de Han JE1BMJ
>
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