[Amps] SMPS Question

[TexasRF at aol.com]

Also in reply to Charlie, re: why not used more often.
 
Back in bygone days we were allowed to run 1 KW power input for cw or 2000  
watts input peak input for SSB and other modes. Many, if not most of the  
commercial amplifiers were designed to tune up with a cw carrier and 1000 
watts  input power. These amplifiers typically had a cw/ssb switch on the front 
panel  that changed the plate transformer primary or secondary tap to cause 
the  plate voltage to increase about 40%.
 
The idea was you could tune up at 1000 watts input, make the switch, adjust 
 the drive level enough to increase the plate current about 40% and end up 
with  2000 watts input power and the have the same plate load impedance.
 
It was illegal to make the switch and adjust the drive level using a cw  
carrier as that would always exceed the legal input power limit of 1000 watts. 
 Of course no one ever did that, right?
 
So, the scheme has been around for a long time; just not described as we  
have been discussing here recently.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 7/24/2015 10:30:07 A.M. Central Daylight Time,  
chris at chriswilson.tv writes:



Hello Charlie,

On Tuesday, July 21, 2015,  you  wrote:

> Along the same vein as Colin, I have an adjustable 0-4kv,  0-2.5Amp SMPS. 
It
> has a switch freq of 18 khz.

> Will this  allow to change the Ep, and not retune?

> If so, why not use more  often? Seems like an efficient way to go. Much
> lighter, and voltage  regulation is <1%.

> What am I missing?

> Charlie  N6CFH


I would be most interested in seeing photos and a schematic  of this,
or a similar high voltage, high current SMPS, either home brew  or
commercial. The tight voltage regulation, and not having to put  my
back out lifting huge linear supplies is very appealing!

A big  thanks to Manfred too, for another fascinating post on  SMPS
matters.

I run a big transformer that gives 5kV at well over an  Amp off a 25
Amp variac. I mainly run it with the variac switched out, but  it's a
very useful beast for general HV supply duty, and regulation,  looked
at on a scope with a loosely coupled coil winding, is pretty good  even
with the variac giving about 180V AC into it, instead of our UK 240V  @
50Hz. It's just so *BIG* though, in a castored cabinet, and would  need
dismantling to safely get it down the stairs from my upstairs  "shack".




-- 
Best regards,
Chris        mailto:chris at chriswilson.tv

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