Not very practical for your application, but about 50 years ago, my
father's company (http://sujan.hallikainen.org/hi/ ) had an interesting
way of generating 50Hz for equipment they shipped outside the US. This was
process chemical analysis equipment for oil refineries. It measured
viscosity, boiling point, specific gravity, color, etc. of petrochemicals.
Their method of generating 50Hz consisted of two three phase motors
connected together. One would rotate the other at a relatively slow speed.
On the one being rotated, they drove the armature (I think it was) with
60Hz. They got 3 phase 50 Hz off the field windings. The rotation of the
shaft subtracted 10Hz from the 60Hz.

There is, of course, test equipment to generate various line frequencies.
My former employer had a couple of these units. I used them a lot in the
design and testing of phase control light dimmers. In those dimmers, the
PIC would time between zero crossings of the AC line on power up, then
decide which table to use in converting from DMX values to timer clicks.

Your idea is probably the simplest. Are the 50Hz countries you're shipping
to 120V or 230V? It seems that most 50Hz countries use a 230V line, so you
would not need the transformer.

Good luck!

Harold



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