Introduction: 50 CYCLE GENERATOR

About: Last time in my life that I saw the moon that close to me... I was born in the capital city of a country that no longer exists.... I'm in my own timeline and an Electronic Engineer... Received my first degr...

Here you see a large alternator providing 50 Cycle AC Power and is shaft driven by a 60 Cycle motor.
Called a Motor Generator used to test equipment I occasionally designed for England, Europe and Australia.

Step 1: MOTOR

The motor is an old 7420 Frame 115VAC 9.6 Amperes  1725 RPM  1/2 Shaft Horsepower  60 Cycle  Continuous Duty  machine.


You need to find a set of pulleys with differing diameters to translate the motor's 1725 RPM to the alternator's 50 cycle output.

These machines are how 50 Cycle power was generated before
the semiconductor was invented at Bell Labs.
And were known as MG Set  ( Motor Generator Setup ).

Well ... Yes ... Vacuum Tubes like the Thyratron tube
which is the Vacuum tube equivalent of the SCR Silicon Controlled Rectifier
and Mercury vapor tube devices could make 50 cycle electronic supplies
before the advent of semiconductors.

Of course tubes generate Heat and take up a large volume even compared to the MG Set.

Here is a video what they looked like long ago.

Video By Radu Motisan


A short video of this MG running in the lab.
... Only about 15 seconds ...


The MG Set has a  simple motor has an On / off switch
Power comes through the gray power cord.
The system diagram shows the 60 Hz input power  Motorswitch  with a  duplex outlet
The output power 50 cycle wiring feeds the right half of the  Double Duplex outlet

Only the 100 VAC Outlet is active all the time when running..
When 240 VAC is needed,  the transformer is plugged into the Right 100VAC outlet .
This delivers power to the Left  240VAC 50 Hz outlet.

The transformer is designed for both 50 and 60 cycle operation.
That means it has been designed for 50 Hz and will run even cooler at 60 Hz.


Storing MG unit under another machine in my shop.



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    6 Discussions

    AH! Excellent you constructed a power converter set. My experience with a converter set was about 30 years ago in the US Air Force when I was stationed in Germany. Our radios were set to run on 60 Hz and the German power grid is 50 Hz. The driving motor was a 600 hp 50 Hz motor direct coupled to a 60 Hz Alternator it ran very well.

    3 replies

    600 HP Wow,  makes sense for the Air Force.

    As frequency goes up magnetic weight goes proportionally down.
    WWII bombers and many military transports use 400 Hx (cycle).

    Most of the younger crowd probably have never seen an MG cycle converter.  Thanks for sharing.


    Your Welcome.

    The reason for the large converter set was that at that time there were 40 single channel transmitters at my base being powered. They were of the WWll tube type and the chassis were the size of footlockers. The radios were later upgraded to transistor types, then the power requirement was reduced, DRASTICALLY. The converter set was no longer needed as the power supplies of the new radios could be selected to run on 50, 60, or 400Hz, AC voltages from 90 - 265 vac. and also almost any DC configuration.

    Electronic power supplies have com into their own since or about the time Apple got involved.
    As you point out 50 through 400 Hz and 90 to 240+ VAC and sometimes DC if the device has input to that stage of the UpDownVerter.
    Impressive techno world.