Rotary converters are still viable today. In areas where three phase power is either too expensive or completely unavailable, a rotary converter can be purchased to run three phase motors. For instance, in my area three phase is available, but prohibitively expensive for casual usage. If I could locate a surplus bridgeport or medium size engine lathe it would be considerably cheaper for me to purchase a rotary converter than attempting to retrofit the machine's power plant or acquire three phase power. 20 years ago I wanted to run three phase to my shop. To run the lines 40 feet and install the transformers the poco wanted $20k. The service was going to cost $900 per month + usage. I opted against :-) I truly do not understand why my local poco is so prejudice against running three phase to commercial locations, but they are. I run 5 tons of refrigeration and 9 tons of HVAC, in most areas three phase would be a cost effective alternative, but that power bill only averages $850/month using single phase. A buddy of mine in a different area has a wood shop with three phase power, his bill is never over $400/month, and he has a 75hp shaper that surely spikes the demand meter every time he flips the switch. Locally I know a man who owns an ice plant, in the summer his power bill is upwards of $25k/month! Another local business was purchased by a larger corporation several years back. The site is physically adjacent to a nuclear power plant. The large corporation sent in a EE team in an attempt to reduce the power overhead, which was averaging $1.5M/Month. At the end of the analysis the EE's determined that the plant's usage only warranted ~$500k/month. The corporation went to the poco and discussed the disparity in an attempt to re-negotiate the rates. The then CEO of the poco listened patiently to the presentation and then told them that the poco had no intention of lowering their rates. The team left, and a week later they announced their intention to build a large steam generation plant; and that the nuclear plant would be required to purchase the excess steam in accordance with federal guidelines. When completed, the plant would be required to purchase an estimated $250k/month of their excess steam. While the plant and the poco are distinctly different entities, the then CEO of the poco had a very sudden career change. The local papers and TV news had a field day, but local rates remained unaffected ;-) The new CEO of the poco obviously correctly ascertained that there were no other customers capable of circumventing their pricing structure. I never read or heard what the then CEO of the poco was making in salary, but loosing that particular account (regardless if the revenue was $500k/month or $1.5M/month) obviously angered the poco's board, and I would suspect the nuclear plant's parent company was less than happy to be required to accommodate their new neighbor's plans, though I suspect this was less annoying than dealing with the NRC. I have often wondered if the then CEO would have had the same career change had he decided to reduce the rates, perhaps met them half-way? Probably. I am not, in general, a conspiracy theory supporter, and I certainly have no affinity for my local poco; however, the track record of ADM:http://en.wikipedia.org/wiki/Archer_Daniels_Midland
is somewhat darker than our little po-dunk poco. The local media fell just short of portraying ADM as the "David who slue Goliath", but the undertones were certainly present. I viewed it more like Goliath stepping on an ant, not out of any particular meanness; rather, oblivious to the trivial toils of the ant, aware only of the steady march along their path.
Off the soap box :-)