WVProfessor
New Member
I am trying to learn the ancient art of magnetic amplifiers. Not power supplies but real DC operational totally magnetic amplifiers.
I saw a schematic of a magnetic amplifier once at the University of New Orleans Physics Lab. It was used to amplify the millivolt output of our laboratory gaussmeter up to a volt or so to control the current in the big magnet. It's gain was set by a feedback resistor just like a real op-amp. The circuit was powered by an audio frequency AC source. There were at least two inductors and at least four windings. I cannot understand how the two gain stages were connected or how the output was rectified to DC without phase sensitive detector diodes. Maybe it was a chopper but the frequency, I think, was about 2KHz. I saw no semiconductor devices at all in the schematic, only transformers and resistors and few capacitors. The DC gain was around 1000.
I have some tape wound toroids waiting to be wound with wire, to make a home made two stage amplifier if I can get some good ideas.
The important principle here is that saturation will reduce the inductance of a winding on a piece of iron. And it is easy to saturate a big piece of iron with a low voltage DC using plenty of turns..
I built a DC ammeter that used two highly saturable toroids driven by AC, a phase sensitive detector and a feedback winding. All that stuff was easy compared to the magnetic amplifier mystery.
If you can find me someone who knows about this subject, I would be very grateful.
I saw a schematic of a magnetic amplifier once at the University of New Orleans Physics Lab. It was used to amplify the millivolt output of our laboratory gaussmeter up to a volt or so to control the current in the big magnet. It's gain was set by a feedback resistor just like a real op-amp. The circuit was powered by an audio frequency AC source. There were at least two inductors and at least four windings. I cannot understand how the two gain stages were connected or how the output was rectified to DC without phase sensitive detector diodes. Maybe it was a chopper but the frequency, I think, was about 2KHz. I saw no semiconductor devices at all in the schematic, only transformers and resistors and few capacitors. The DC gain was around 1000.
I have some tape wound toroids waiting to be wound with wire, to make a home made two stage amplifier if I can get some good ideas.
The important principle here is that saturation will reduce the inductance of a winding on a piece of iron. And it is easy to saturate a big piece of iron with a low voltage DC using plenty of turns..
I built a DC ammeter that used two highly saturable toroids driven by AC, a phase sensitive detector and a feedback winding. All that stuff was easy compared to the magnetic amplifier mystery.
If you can find me someone who knows about this subject, I would be very grateful.