Re: [Electronics_101] RE: 1-phase -> 3-phase transformer?
- Thanks for taking the time to report your experience with building a single phase to 3 phase converter using capacitors, sometimes called a static converter and a rotary converter, also called an idler.
The other Howard
On 9/24/2013 9:15 AM, A6intruder@... wrote:
I’ve been though most of this discussion. I acquired a “free” three phase air compressor that I wanted to use at my home shop. I worked for a company that had lots of used motors and electrical gismos sitting around.
First thing I tried was the factory built capacitor circuit that was supposed to run my 2Hp three phase air compressor from my house single phase 220V. For whatever reason it did not work – maybe already past useful life?
Second, I tried the idler motor system with its associated capacitors. Following the directions I found on the internet, I purchased supporting capacitors on eBay and set up a panel complete with appropriate fuses on each leg. The problem I ran into was uneven current between the three legs. I kept blowing a fuse on one leg. Further research showed that I probably needed a larger selection of capacitor values to find the correct balance. It also appeared that the “correct” value of capacitor would depend on the load…At this point I had spend $60-$70 on capacitors and I wasn’t gaining any confidence with the process. My overall goal of having a reliable air compressor was turning into a significant project (it was just a tool after all) so I finally spent the big $$ and bought the appropriate single phase motor to run my compressor.
For those of you mathematically proficient it might be possible to calculate the correct capacitance values for the idler circuit but I could not find enough reference material to work that angle.
So I can say the idler circuit did work but in my case it didn’t work well probably due to my limited knowledge and experience.
I know in the late 1960’s my grandfather installed two grain bins in rural Illinois. There was only single phase power to the farm and he had two 7.5hp 3-phase fan motors to run. The power company installed a motor alternator system right at the base of the power pole that held the transformer. So he had a single phase motor driving an alternator and he had good quality 3-phase power to run his fan motors. I’m sure it wasn’t cheap but it was the solution that lasted for years, might still be running for all I know.
If I ever get a Bridgeport vertical mill for my home workshop (they normally have a 2Hp 3-phase motor) I will be investing in the VFD that accepts single phase input and gives 3-phase output. It will be worth every cent to do the job right with today’s technology.
What you guys are talking about is called the Steinmetz circuit.
I see no reason why it woulnd't work to some extent with a transformer instead of the motor, but it may work even worse than it does on the motor especially for variable loads.