Potential Transformer
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From: Phil Allison on 20 Jan 2006 00:12 "John Larkin ** Big noting yourself like this does not work with me. In fact, it makes you look like a pathetic jerk. > Why would I care how I look to you? ** Missed the point - yet again. What a complete goose. >>>>>>Small mains toroidals generally have no such issues. >>>>> >>>>> What makes a toroid different? >>>> >>>> >>>>** Very low Imag when used within ratings. >>>> >>> >>> Any core can be run at low Imag. The shape doesn't matter. >> >> >>** You are quite wrong, yet again, plus missing the point entirely and as >>usual. > > > You might be a tad more specific. ** I have been as specific as possible. Better re-read the thread. > So how does the shape of the core > affect the available Bmax? ** More of Larkin's red herrings. So the posturing clot has no knowledge of toroidal transformers either. >> The point related to using " any ole " transformer". >> >> Remember those words ?? > > Sure. Most any AC power transformer will make a decent PT for > metering. ** Now the posturing clot comes around full circle. Yawn. > And this is a school project... ** No it is not. Try reading the OP's post properly. Try reading any of mine properly. Make a nice change. ........... Phil
From: John Popelish on 20 Jan 2006 00:22 Phil Allison wrote: > "John Popelish" > >>Phil Allison wrote: >> >> >>>>If so, you might look at some toroidal transformers with dual primaries >>>>(115-230). They have quite good voltage regulation under light load. >>> >>> >>> ** That last bit looks like a tautology. >> >> >>It is pretty close, as long as the core is no where near saturation. If it >>is near saturation, a slight change in voltage or frequency can change the >>input to output ratio. When dealing with instrumentation instead of power >>transformers, you have to be more flexible with the concept of regulation >>than just load current regulation. ;-) > > ** That is purest gobbledegook. > > The term "voltage regulation" when referring to transformer is related to > load. > > The term you needed and should have used was was " voltage linearity" . Thank you.
From: John Popelish on 20 Jan 2006 00:23 Phil Allison wrote: > "John Popelish" > >>Phil Allison wrote: >> >>>"John Larkin" >>> >>> >>> >>>>Use a resistibe voltage divider. Or a series resistor into a small >>>>audio-type transformer, operated in current mode. Or any ole 240-to-6 >>>>or whatever transformer. You'll probably have to to a phase tweak >>>>somewhere in the system anyhow. >>> >>> >>> >>> ** Using "any ole" transformer is bad advice. >>> >>>Small E core mains transformers have high and non linear magnetising >>>currents - so the output waveform is distorted and does not follow >>>input voltage changes linearly. There is often significant phase shift >>>as well. >>> >>>Small mains toroidal generally have no such issues. >> >>Agreed. That is why I offered an example of a toroidal, 50-60 Hz >>transformer. > > > > > ** Shame you gave a fallacious reason. > > Good thing the true one is now posted. (hanging head in shame)-;
From: John Larkin on 20 Jan 2006 00:21 On Fri, 20 Jan 2006 16:12:08 +1100, "Phil Allison" <philallison(a)tpg.com.au> wrote: > >> And this is a school project... > > >** No it is not. > > Try reading the OP's post properly. > Are you insulting the South Dakota School of Mines and Technology? That's not nice. John
From: John Larkin on 20 Jan 2006 00:52
On 19 Jan 2006 11:43:48 -0800, "Kit Talich" <Oxmmdox(a)gmail.com> wrote: >Hello all! > > I am currently working on my senior design project of a Digital >Power Meter here at the South Dakota School of Mines and Technology >(Shamless plug!). I plan to measure and display Voltage, Current, Power >and Power Factor. To do this I plan to sample both waveforms and >calculate the rest. I have found a Hall Effect type current sensing >chip. While I have found a few 120V-5V PT's my personal requirements >are 230V 10A. Potential Transformers that accomplish this feat seem to >be a little more rare. Does anyone out there know of somewhere I can >find some of these? Small size would also be desired. > > >P.S.: Gimme a JOB! B.S. EE minor:CSC Transformers aside, what sort of sample rates do you plan to run? Will you sample E and I simultaneously, or is there a single mux'd ADC? Any ideas on processing algorithms? Getting an electronic meter to, say, the accuracy and dynamic range of a rotating-disk meter is surprisingly difficult; those puppies have probably had thousands of engineer-years applied to their development, and they are *good*. John |