power controller

[roo7flat5]

I came across a circuit at EDN Design Ideas 1/7/99 that uses a fan
controller to switch back to back SCR's via a 1:1:1 pulse transformer to
control 1-3kw (a.c. mains) load.
What is the difference between a 1:1:1 and a 1:1+1 pulse transformer?
What rating would the SCR's have to be...half or full current rated?

 

[Brian Goldsmith]

"roo7flat5" <roo7flat5@dodo.com.au> wrote

I came across a circuit at EDN Design Ideas 1/7/99 that uses a fan
controller to switch back to back SCR's via a 1:1:1 pulse transformer to
control 1-3kw (a.c. mains) load.


What is the difference between a 1:1:1 and a 1:1+1 pulse
transformer?


*** They are the same.

What rating would the SCR's have to be...half or full current rated?

**** Full current rating.
Brian Goldsmith.

 

[Bob M]

Hi there,

When I was a kid, I wanted to build an AC mains controller as well.
Getting 1:1:1 pulse transformers turned out to be difficult and
expensive. After some investigation, what I did instead was use a full
wave bridge rectifier, 1 SCR, and an opto isolator.

One side of the AC mains is directly connected to the load. The
remaining side of the AC mains is connected to the AC input of the
bridge rectifier. The other AC input of the bridge rectifier is
connected to the remaining side of the load. The SCR is connected
across the + and - terminals of the bridge rectifier.

Finally, the opto isolator and a couple of resistors are connected to
control the gate of the SCR.

At the time I built this (Apollo moon launch days), opto isolators
were cheaper than pulse transformers, and bridge rectifiers were
cheaper than SCRs. Additionally, the opto isolator can be directly
driven by TTL or any micro. Both the SCR and the bridge rectifier must
be rated to carry the full load connected to the AC mains.

I absolutely suck at ascii diagrams, so if you need one, send me an
email and I will send you a diagram that you can display with
Microsoft Word.

Cheers from Canada!

Bob Morgoch

"Brian Goldsmith" <brian.goldsmith@nospamecho1.com.au> wrote in message news:<0va9b.102704$bo1.91204@news-server.bigpond.net.au>...

"roo7flat5" <roo7flat5@dodo.com.au> wrote

I came across a circuit at EDN Design Ideas 1/7/99 that uses a fan
controller to switch back to back SCR's via a 1:1:1 pulse transformer to
control 1-3kw (a.c. mains) load.


What is the difference between a 1:1:1 and a 1:1+1 pulse
transformer?


*** They are the same.

What rating would the SCR's have to be...half or full current rated?

**** Full current rating.
Brian Goldsmith.