Welder 1 - WTF is a Saturable Reactor?

A saturable reactor is an arcane piece of electrical kit that modulates a large AC current with a small DC input. This unit was removed from a Bridgeport Series II CNC milling machine where it was used to regulate the power supply to the stepper motor drivers that moved the X, Y, and Z axes. In this video I describe how it works and demonstrate it's operation.

[@lbochtler]

its basically a magnetic amplifier. very old technology that i find absolutely fascinating.

[@sylkelster]

VERY hard to find. I own three 'tri-core' types of varying sizes, with the largest at about 1kVa. I've been actively looking for a large unit (10kVa+) to control a utility pole transformer for a giant tesla coil for years. It really is like looking for a literal needle in a haystack. The few people who have them usually end up scrapping them or incorrectly list them as a transformer. The one or two companies that still make them (for use in harsh non-solid state friendly applications) demand outrageous prices for them. Definitely a unicorn find and my favorite magnetic device.

[@Greg_Chase]

What's happening in these devices is a bit unusual especially if you're used to semiconductor-based amplifiers, or older vacuum-tube amplifiers. The magnetic core, once it is purposely saturated by (a pretty low) DC current in the control coil winding, alters the behavior of the inductor (one of the coils, not the control coil) and allows AC current to be applied to that coil and pass freely. So the small DC current is like an on-off switch, the "on" mode being reached by the core become magnetically saturated when DC is passed through the control coil. It's an amplifier - a small (DC) signal can control (a much larger) AC signal. If you need to switch high AC power, and don't have a tube or transistor handy, this is an old way to do it. Very nice example you have there - I have seen the 'figure 8' variety but not an example like this, where the control coil surrounds the two 'amplifier' coils.

[@trollforge]

Very interesting project!

[@Lyrandar]

Oh man. First update in a while