Motor generator

On May 4, 2021, at 5:03 PM, Jon Elson via cctalk <cctalk at classiccmp.org> wrote: ?On 05/04/2021 06:06 PM, Donald via cctalk wrote: Nope. I know the 360/50 and 360/65 used a "converter-inverter" that converted 208 3-phase to about 280 V DC, then inverted it with a 4-SCR inverter feeding a resonant transformer to create 120 V 2.5 KHz regulated single-phase sine wave power. All the critical loads in the CPU ran off this power. Notably, the I/O power sequencer and console lamps power supply did not run off this power. The converter-inverter made an absolutely HORRIBLE whine that could be heard 20+ feet from the back of the CPU even in a very noisy machine room. The only "360" machine I know of that used 415 Hz was the Model 195, although I can guess that the 360/85 used 415 Hz also, as it was essentially the prototype of the 370/165. The 370/145 used an internal motor/generator set in the back of the CPU cabinet to produce 120 V 415 Hz 3-phase power. Larger 370's generally were provided with UPS's instead of M/G sets to create the 415 Hz power. Also, the 709X series ran off 400 Hz from a motor/generator set. The 360/50 and /65, at least, were pretty sensitive to noise and short dropouts in the mains supply. The 370's with the MG sets rode through pretty severe power dips with no effect at all, until the disk drives and tape drives went offline. Jon