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.

Step 2: CONNECTING MOTOR TO GENERATOR

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

Step 3: WATCH IT RUN

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

Step 4: WIRING THE SYSTEM

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.