Purchased power as applied to plate glass manufacture

C. W. Fick (communicated after adjournment): Mr. Harrington´s very interesting paper may raise the question of why this arrangement of vertical synchronous-motor drive is not universally adopted by the plate-glass manufacturers. There are some twenty plate-glass plants in this country with a total of 100 to 125 grinding and polishing machines. Of this number a majority must operate for a short time at slow speed at the beginning of each operating cycle, due to the method of lowering the grinder and polishing disks onto the glass. Thus, the synchronous motor is eliminated for these cases, unless a frequency changer and double bus arrangement is used.