I’m trying to help a distant (location) friend get a vintage (1950’s) lathe running. It has 3phase 220v input and the motor is two speed DC. 115v field, 200v armature (motor & drive by Louis Allis Co). He does not have 3-phase power. We are hoping to convert the drive to single phase rather than scrapping the whole setup and using a 3ph motor & VFD. His pics show a bewildering array of transformers, heat sinks and slide wire resistors. From his description I’m guessing the 3 phase feed is transformed into 115v & 200v 3phase and then these are rectified to 115v & 200v dc output. The 115v dc would then go to the motor field. The 200v dc would be split to feed the 2 sets of armature leads by a Hi/Lo switch. Then through a two section stacked Rheostat for infinitely variable speed to the armature leads. I would think the 3phase rectification circuits could be replaced by single-phase full wave bridge rectifiers (plenty of heat sinks available). Could the three-phase step down transformers be wired for single phase? Any comments or anyone familiar with this type of drive?
