[ARC5] Army/Navy transmitters from a NON COLLECTOR viewpoint, the ham version...

[Kenneth G. Gordon]

On 11 Feb 2020 at 17:01, Brian Clarke wrote:

> 
>     Hello Kenneth,
>      
>     Not just transformer-less power supplies. Most Voltage doublers are effectively half 
>     wave; some Cockcroft-Walton designs are full-wave - but they are quite complex.

In fact, that is exactly the design I am using. I don't consider them complex to wire, although 
they may be a bit complex to understand.

> With 
>     consumer-level Voltage doublers, DC does get back through the mains transformer 
>     because with half-wave rectification, only one half of the mains cycles are loaded. So, 
>     the transformer core is compromised, too.

I don't use half-wave designs. Never have. Don't like half-wave rectifier circuits. In fact, I 
usually replace half-wave circuits which show up in any of my equipment with full-wave 
designs. I could never understand the "economy" of half-wave.

>      
>     The mains distribution board fuse or circuit breaker is unlikely to trip. Its main purpose is 
>     to prevent fire in the wiring hidden inside the walls that services the power outlets.  You 
>     probably have 60 A fuses / circuit breakers

No. 20 amp for all new (#12) wiring I installed (I am an electrician), and 15 amp on those old 
circuits with #14 wire I couldn't reach to change. In our home, we still have "knob-and-tube" 
wiring to at least one circuit, but it is safe.

I do have one 30 amp circuit to my SB-220 amp, and of course there are two larger circuits 
for the electric range and for the dryer.

> for each mains circuit with NEMA-code 
>     wiring, and a 200 A fuse on the phase wire incoming from your local pole pig.

Yes. The panel is a 200-amp panel, so the main-breaker is a 200 amp.

>     However, equipment fuses are there for a different purpose -to protect the equipment - 
>     and hence, should be selected for their time vs current performance for each piece of 
>     equipment, with perhaps a 20% continuous overload. As you have bumped your 
>     smoothing filter capacitor from 150 to 640 uF, you have more than quadrupled the 
>     start-up surge load. And if you have used modern, low-ESR capacitors, all the rage 
>     these days, the start-up surge may be even higher. One hidden effect of such surge 
>     loading is that the turns inside the transformer starts to jump

...unless the transformer was designed for it...

> about and may hit the 
>     laminations, especially if an accountant has designed the transformer, giving intermittent 
>     shorted turns.
>      
>     Actually, the average load does increase with Voltage doubling. The rectification 
>     efficiency is lower than with full-wave rectification.

Which is only ONE reason I never use half-wave rectifier circuits.

>     When I have made changes to increase the filtering, rather than rely on the resistance of 
>     the transformer primary, I use a very simple soft-start circuit; I use a mains Voltage rated 
>     SPST relay, its solenoid across the transformer primary, with a resistor (select on test - 
>     usually about 10 Ohm) across the NO contacts in series with the incoming mains. If you 
>     don´t have mains rated relays, use a lower Voltage one across one of the lower Voltage 
>     secondaries, eg, a heater winding.

Yes. That is a good, un-complicated, reliable, soft-start circuit and one of my 
favorites....when I use one.

>      
>     Cheers es 73 de Brian, VK2GCE

And vy 73 to you, Brian.

Ken W7EKB