[Amps] SCR to adjust 240v to 200v

[Roger (K8RI)]

I've used a lot of high power SCRs in industry and built controllers 
using them.
As Roy said, they will likely prove to be very difficult because of the 
tremendous hash they create.

An SCR is turned on somewhere during one half of the AC cycle. A second 
SCR handles the other half. The turn on leads to a very fast rise time 
into an inductive load (the transformer). This creates a ringing through 
a range of frequencies, much like a lightening strike.
There are ways of taming this, but In plain language, I think you will 
find this approach a royal PITA
I again agree with Roy, that another transformer used in a bucking 
configuration would be the most economical and probably easier than 
replacing that transformer.

73

Roger (K8RI)


On 8/12/2016 Friday 1:07 PM, Jim Durham wrote:
> Hello all,
>
> This is my first posting, so Howdy..
>
> I have a Henry 2k-2 (modified to take 3-500Zs).  After I bought it, 
> some years back, I fired it up and tube filaments were very bright and 
> HV was high.
>
> Talked to Henry. They asked me the plate transformer number, which 
> they looked up and said "Oh, that's the 200v European transformer". 
> So, I put a hefty variac on the 240v AC incoming and all is fine, 
> except I'd like to ditch the variac and was wondering about if anyone 
> on here had any wise words about using an SCR instead to back the AC 
> voltage off.
>
> My experience with big SCRs (TV studio lighting) was that they tend 
> to  put out a lot of RF hash.  I also wonder about how the choke and 
> filter cap in the power supply would like non-sinusoidal AC waveform?
>
> Anyone have any experience with this?
>
> Thanks and 73,
>
> Jim, W2XO
>
>
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