High power DC (AC) rotary generator

[Salvador12]

I know back in the day many places where high power was needed used a rotary machine whether DC or AC. This has been largely superseded by semiconductors and other solid state technology. But I do wonder though would there still be a need or a market for a high power DC generator for example which could output if needed in the megawatt range with controllable voltage and a pure DC output (no AC ripple) ?
Or for that matter a generator that can output both DC as well as AC with a variable frequency as needed. Where in the AC case the output frequency and waveform is not related to the shaft RPM but can be controlled separately like in an amplifier.

I tried google for various power supplies for stuff like water to hydrogen electrolysis or aluminum fabrication or others but I can't find what they use there nowadays.

 

[Salvador12]

Well I do get the attraction to label this is as something out of 19th century etc, truth be told it was first invented by Faraday in the 19th century but the underlying physics works nevertheless.
the interesting part is that the excitation magnet can rotate together with the current generating disk or parts of conductor. This way you can slice of the otherwise monolithic disk and produce so called pole-pairs. Say 4 pairs. so in two disk sections current goes from center to rim while in the other two from rim to center. Then put a sealed liquid metal channel at the rim and inside that channel is a moving electrical contact controlled by a motor.
Spin the generator, apply a variable frequency to the contact motor and your contact now moves with a different speed than the rotor itself. This way one can control the output voltage. Then one can take the produced current from the shaft at the center of it which is easier than from the rim or periphery of the rotor.

In DC only case one could stack up such planar rotor sections and produce a very large current easily, even moderate voltage given a larger radius is chosen.
For a larger diameter rotor and moderate RPM (1500-3000) one can easily generate couple hundred volts at MA of current if needed.

The thing is I am not sure whether there are areas that still would benefit from something like this,

 

[D.A.(Tony)Stewart]

Well I do get the attraction to label this is as something out of 19th century etc, truth be told it was first invented by Faraday in the 19th century but the underlying physics works nevertheless.


In DC only case one could stack up such planar rotor sections and produce a very large current easily, even moderate voltage given a larger radius is chosen.
For a larger diameter rotor and moderate RPM (1500-3000) one can easily generate couple hundred volts at MA of current if needed.

The thing is I am not sure whether there are areas that still would benefit from something like this,

DC motors are useful, but as generators with large inductive loads, DC can be a problem to transfer the load stored energy when switching off, without a zero-crossing current to extinguish the arc.

 

[Easy peasy]

Then put a sealed liquid metal channel at the rim and inside that channel is a moving electrical contact controlled by a motor.

this is the bit that you will find interesting - you have obviously never been in contact with any health and safety legislation .....