# Transductors/Magnetic amplifiers and power supplies

Discussion in 'General Electronics Chat' started by recklessrog, Mar 20, 2016.

1. ### recklessrog Thread Starter Member

May 23, 2013
349
102
I don't want to hijack another thread, but electrophile started a thread.... Non-contact AC blocking. Some posts, including mine referred to Magnetic amplifiers, so I'm starting a new one as it is a little off tangent from his original post.
Having worked with Magnetic amplifiers/ Transductors many years ago, my interest in them has been re-kindled by his post, leading me to conduct some experiments as to how to make a regulated power supply that is somewhat different from the norm. (ie. AC in AC out)
I hope analogue kid (and others of course) will contribute some ideas, as I have a feeling that many, like me, prefers analogue power supplies to switch mode. ( With me, I think It's an age thing!!!)
My Idea is this:- Make a powerful, variable and stabilised AC in AC out supply with none of the control circuit connected to the mains (line).
A simple way of describing how a Transductor works is that by applying a small DC current to a winding, the core saturation can be controlled. Think of a load connected to AC via a large value choke. with enough inductance, very little power will reach the load due to the reactance of the choke.
If we reduce the inductance, the reactance becomes less and power will be able to be drawn by the load. At zero inductance, the only thing that will affect the output is the resistance of the winding.
Controlling the saturation of the core by applying a DC voltage to a separate winding, the power delivered to the load is also controlled.
One of the problems though, is how to keep AC being induced from the load winding out of the control circuit, so what I see is this:- Have two identical
load windings connected in series but in opposite phase to cancel out the coupling of AC into the common DC winding,,
Use a separate current transformer in series with the load to supply feedback to a standard regulator IC such as the ubiquitous 723 and bypass BJT feeding the DC winding.
My experiments so far In only a couple of days, have proved that I can easily vary the power to a 3kW heater with a couple of toroidal chokes and very small dc saturation current. I am now thinking about the design of a suitable regulator. ( as I have about 20 723's and dozens of 3055's, it looks like that's the way to start)
Lets see how this goes, any suggestions or criticisms are most welcome

2. ### GopherT AAC Fanatic!

Nov 23, 2012
6,330
4,072
Schematic(s)?

3. ### recklessrog Thread Starter Member

May 23, 2013
349
102
Early Days at the moment, as soon as I've got the control circuit working, I will post what I have for more input.