What is the typical voltage and frequency of the electrical generator in an airliner?
A constant speed drive (CSD) converts the rotation from the accessory gearbox to a predetermined constant rotation rate.  The rate of the accessory gearbox is directly related to the high pressure spool (N2) rate and changes with power adjustments.

The CSD will ensure its rotation rate is constant.  The Challenger 604 CSD rotates at 12,000 RPM and outputs 115 VAC @ 400 hertz.  Its max output is something like 30 kVA or kilovolts-amps.  Since we are talking AC power, it is not appropriate to call that watts.  The AC power is converted to 28 VDC by the way of transformers called transformer rectifier units (TRU).