On Saturday 03 August 2019 23:30:47 John Hasler wrote: > A static converter doesn't produce three phase. It converts a > three-phase motor into a capacitor start, capacitor run single phase > motor by connecting two of the phases to the single phase lines and > connecting the third phase to one of the lines through capacitors. It > only works for motors and needs to be tuned for a specific motor. > > A real motor generator set *will* produce 60 Hz three phase because > the motor and generator will be synchronous. The power will also be > seperately derived (not connected in any way to the single phase). > > More comon than real motor-generator sets are "rotary converters". > These are large three phase motors wired up like the static converter > discussed above but with slightly different capacitor values and not > connected to any mechanical load. Three phase loads are then > connected to the phases of the motor. This produces a fair > approximation of three phase but note that two of the phases are > connected to the single phase lines. This means that you have neither > a neutral nor a grounded conductor (unless you are in Europe in which > case you have > corner-grounded delta).
Three phase, at most any frequency can be had a lot cheaper at up to 10 horse or so by using a suitably sized VFD. I'm useing 2 1.5 horse rated, to drive a 1 horse 3 phase motor, currently available from ebay for about a hundred bucks. Top frequency is 400 hz, but motor inductance reduces the drive currant to under an amp a phase at around 200 hz, so theres little torque to do work above 150 hz. But I can get turn the house around torque at 5 hz, not forever because the motors fan does not move cooling air when its not running at normal speed. But for a 20 minute job its fine. Lathe itself has an 8 speed drive, rarely changed out of 5th, the vfd does it all. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
