Run a 120V/60Hz motor at 230V/50Hz
The power mains voltage in Ireland is 230V and the frequency is 50Hz.
The power mains voltage in the USA is 120V and the frequency is 60Hz.


To power a 120V motor from 230 volts, you need a step-DOWN transformer.

It is very unlikely that you have a "30Hz" motor. There is no commonly available mains utility power on this planet that operates at 30Hz.

If your (likely) 60Hz motor is actually mains-frequency sensitive (which many/most motors are NOT), then it will operate at 5/6 the speed compared to North America (60Hz).  Since you did not identify what this motor is for, you will have to make your own determination whether this is significant.

To answer your original question, NO, power converters (transformers, etc) do NOT change the power frequency.  But for 98% of appliances, this makes no difference.