AC Voltage Regulators

They also make electro-mechanical ones that don't use relays. These may be a better thing for you to think about. Imagine an object that looks mechanically like an AC motor.

The stator is much as you would expect in the AC motor.

The rotor has a winding on it that is only part of the secondary turns.

If you imagine the stator and rotor windings connected in series, you will see how turning the shaft will vary the turns ratio from less than 1:1 to more than 1:1.

To remove the leakage inductance, a heavy copper strap is used to act as a shorted turn to the leakage.

Ones like these are still in use here and there in China. They are extremely robust but they don't remove sudden pulses of power. They are still worth knowing about because the theory they work on may be adapted to something more modern.

All such devices make matters worse for others. When the mains voltage is low, they draw more current and when it goes high they draw less current. This makes the variations worse. For this reason, they con only be used on a small fraction of the loads if you want the power system to be stable.

Sola "Adjust-A-Volt"

AFAIK they are still used for electrical distribution systems.

The relay system you describe would appear to me capable of only producing step-incremental voltage changes, - not what I would term a "good voltage regulation scheme".

High power systems which I saw used around the 1970's, employed motor driven variacs which produced a much smoother response than relay switched schemes.

That's exactly the units I was referring to (at Pier Exchange in Perth) but it was a lot earlier than the 80's. Several 48Vdc/1000A rectifiers for battery charging.

One good example of such a system is the GE Inductrol, which we used with great success 35 years ago, and is still available.

John Perry

I've seen my share of CVTs, however I only once ever worked on a system with a magnetic amplifier and I don't know anyone else who has.

This is not a magnetic amplifier. This is a variable transformer similar to what was described in my attribution, which you deleted.

The variable transformer adds a controllable small AC voltage to the line voltage, with consequent smooth sine wave output.

Magnetic amplifier operation is very similar in operation to an SCR power controller. In an SCR controller, the control signal causes the semiconductor to be an open circuit until conditions cause it to switch to a low resistance, with consequent waveform chopping. In a magnetic amplifier, the control signal causes the inductor to be a high reactance until conditions cause the core to saturate, switching to a low reactance, with consequent waveform chopping.

jp

It was just an observation.

But isn't this basically a CVT?

Unfortunately, I can't because it is something I saw in the real world.

I have, but they are pretty rare.

Look at magnetic amplifers then.