50/60 Hz motor conversions

From time to time, some of us are faced with a challenge when a customer has a special motor with a rated frequency that doesn’t match the available grid frequency.
Apart from the basic:
Current stays the same,
Torque stays the same,
Speed and HP change in the ratio of 5:6 or 6:5,
What challenges have you met in the field?
What are the effects of a changed speed on the load and how may these effects be mitigated?
What results may be expected when you are not able to easily provide the optimum V/Hz ratio?
Open for discussion.

Was given a task to make a demo unit (incorporating a 1/2 hp motor to drive a positive displacement pump) work on multiple voltages and frequencies (110/220 and 50/60 Hz) for use all over the world.

My “fix” was to install a 220 volt input VFD to drive a 1/2hp 3 phase motor. The 110v power cord was connected to a step up transformer, and the 220 volt power cord was wired direct. So far no reports of sales people blowing fuses or burning down trade shows…

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I like it.
Thanks for sharing.