On 5/5/21 8:07 AM, Grant Taylor via cctalk wrote: > I have found the Motor Generator thread to be fascinating and > enlightening. But it has made many a reference to the 400 Hz or other > frequency much higher than mains line frequency. Despite the comments > about the frequency, I'm still confused as to why the higher than mains > frequency was used.
Iron and filtering. 400Hz means far less iron needed in transformers and variacs (CDC used a three-phase variac at the CPU cabinet for adjustment of voltage). Compare the sizes and it's obvious. Filtering the ripple out of a 2400 Hz 92% DC rectified supply is comparatively simple. A 360Hz supply, less so. In my salad days, I worked at a steel mill where a fair amount of equipment ran from 25 Hz voltage. The transformers were huge in comparison to their 60 Hz cousins. --Chuck
