Thre PHASE CONVERTER

[flintstone mop]

OK Guys
Me and the family visited a fellow and his wife. He is a machinist and repairs these huge lathes and other motorized and computerized tools. His shop had a few of these monsters inside and they run on three phase power. He flipped a breaker and the lights dimmed for a while and this huge motor started up. He explained it was for converting single phase to three. He said it would start and carry a 60hp three phase electric motor. I explained that in our hobby some times we get broadcast transmitters that require a three phase source and some folks convert the power supply to single phase. I didn't ask how much the converter cost.

fred

[WBear2GCR]

It's a no-brainer. You take a three phase (usually 240v) motor of about 25% or more larger than the motor you want to power... run two legs on the 240, and add caps between one leg and the third leg. It then makes 3phase which you wire to the three legs... assuming you "tuned" the caps properly. When you get bigger, and run more juice the receipe gets more critical, and you probably need starting caps, contactors and push buttons to make the thing run right. But I do the simple version of this trick to run a 2hp motor on my old clunker Index milling machine all the time... works jes' fine!

     

          Oh, should work on 3 phase transformers as well...

                  _-_-WBear2GCR

[Bill, KD0HG]

We use those rotary converters a lot in broadcasting. They're called "Phasemasters" and made by a company called Kay Industries. They're used to power 3-phase loads like big transmitters, irrigation pumps  or welders from a single phase source. The biggest one we currently have can produce 75 KW of three-phase AC from a 400 amp 240V single-phase service. It's about 2/3 the bulk of a home washing machine and weighs around a ton.

Phasemasters are actually a rotary transformer. It mechanically phase shifts a portion of the single-phase supply from the utility creating true 3-phase power. There's a big bank of capacitors in the box attached to the motor.

Extremely reliable piece of gear. We've got one in Denver that's been in continuous service since 1984. Once a year you shoot some grease into the ball bearings, and that's it.

Cold starting them under load results in some interesting effects, we measured a momentary draw of > 2,000 amps at 240 volts with the larger one of the two. Almost half a megawatt. Dimmed lights all the way down the mountain for a second. There is a 'soft-start' option available, but we don't have one.
 
http://www.kayind.com/pdf_files/product_data_sheets/t_brochure.pdf

The dynamotor lives on!

[VE1IDX]

The place I just picked up my BTA-1S had a roto-phase unit running their 10Kw solidstate TX and has been doing so for the past 30 years continously without failure.Now that's service.