Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > AC Power and Grounding
3-phase power demonstration
Mike Sokol:
I was just contacted by a company that wants me to train their crew and make a video for them on the differences between the main 3-phase transformer connections, and how to recognize them in the field. Yup, I need to get them up to speed on how to recognize and measure Delta, Wye and Wild-Leg Delta services, as well as 2-pole 120/240-volt service.
Of course it's easy enough for me to create a nice Powerpoint presentation, but I always say that nothing beats a real example. So I'm envisioning how to build a tiny 3-phase signal generator that will make 120/208 volts in WYE, Delta or High-Leg, in a place that doesn't have 3-phase power.
So the thought occurred to me that all I have to do is take any multi-track mixing program, generate a 10 minute track of a 60 Hz sine wave, duplicate it on tracks 2 and 3, then slip those tracks back 120 and 240 degrees out of phase. Then I just output the 3 audio tracks on 3 outputs of an I/O interface like my MOTU Audio Express. Next, I hook up three 120/240-volt primary filament transformers with the 6.3-volt side being driven by the TRS outputs on the MOTU. Finally, I can wire the 120/240-volt sides of the transformers into Delta, Wye or High-Leg Delta configurations with a few banana plugs. Of course, the MOTU can't drive any real amperage through the transformers. But I just need it to make 3-phase voltage in the 120 volt range that can be measured with a DMM.
I don't see why it won't work. Has anyone here tried something like this?
Tim McCulloch:
Ask yourself "WWNTD" What Would Nicola Tesla Do?
Riley Casey:
Nicola would claim wireless was better
--- Quote from: Tim McCulloch on December 06, 2018, 08:25:09 PM ---Ask yourself "WWNTD" What Would Nicola Tesla Do?
--- End quote ---
Mike Sokol:
--- Quote from: Tim McCulloch on December 06, 2018, 08:25:09 PM ---Ask yourself "WWNTD" What Would Nicola Tesla Do?
--- End quote ---
Well, Tesla always said he knew his inventions would work just envisioning them in his mind. He only had to do demonstrations to prove it to other people.
Frank Koenig:
Another approach would be to get your hands on a small, fractional-horsepower three-phase motor. These will work as a (not very good) single-phase motor with power applied to one of the three windings if you give them a spin to get started, which you could do with a starter cord and pully, a la lawnmower (good for dramatic effect). The other two windings will produce power suitably shifted in phase. You would still need a center-tapped transformer to simulate high-leg delta.
--Frank
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