1. Home
  2. ⏚ Electrical Engineering
  3. An (AFAIK) unsolved conundrum

An (AFAIK) unsolved conundrum

Hi, I posted this a couple of years ago in this NG. It generated a heap of
responses and discussion, but I don't believe any of them could be called a
good explanation. I would really like to know the answer, so here goes
again. Maybe there's someone out there that can advise.
THOUGHT EXPERIMENT.
You have an 'ideal' transformer on a toroidal topology, square section core.
The core is quite wide, with the primary on one side, and the secondary,
with an unknown load, on the other. You are given access to the centre of
the core, ie. between the windings, and you are required to measure the
power that is transferring from the primary to the secondary. You have no
access to the windings or input/output connections, otherwise you can do
whatever you want. How do you determine the power flow? Obviously the core
flux is not the answer, it is mostly a function of primary voltage.
Reply to
bruce varley
Loading thread data ...
Ideal? 100% of power in appears as power out. Solved. Ed
Reply to
ehsjr
The OP wanted some way of measuring the power by only looking at the transformer core, not the input or output terminals.
Hint: Although the flux is (mostly) a function of voltage, the MMF (ampere turns) integrated around the closed path of the core can tell you something, particularly if the primary and secondary windings are separated.
Reply to
Paul Hovnanian
Agree, but how does one know the MMF without measuring the current through one of the windings? I think the OP wants to just look at the magnetic parameters in the core, half-way between the primary and secondary windings, and be able to monitor the amount of power flowing.
The flux levels don't change much with the amount of load on the secondary, yet the amount of power flowing through the core from primary to secondary does. The trick is defining the amount of energy *flow* through the core.
daestrom
Reply to
daestrom
If you could measure E and H at all points on a surface surrounding either the primary or the secondary winding, I guess you could calculate a value for power crossing the surface (along the lines of Poynting). So, if you had many sensors distributed in a surface like arrangement, you might be able to calculate an estimate of the power transfer. Right?
j
Reply to
operator jay
Maybe. But how about a method that looks only at the core section between the windings. I think that's what the OP had in mind.
Think about creating a magnetic flux leakage path of a known but high reluctance bypassing the secondary windings with a Hall effect sensor in it. The flux through the bypass should be proportional to the MMF between these two points. The reluctance needs to be high enough so that the flux bypassing the secondary is small compared to the secondary winding flux.
Reply to
Paul Hovnanian
Speaking of leakage flux, I guess we're considering practical transformers, at least to some extent, and dropping the 'ideal' transformer. I imagine this is still in the spirit of the question.
With your measurement, would you get an indication of winding current? Is there more you could derive?
If it turns out that most energy transfer in a transformer is transferred through the core (which seems likely but it's only an assumption) then I guess sensing E and H in a single 'slice' of the core between windings might be sufficient.
Your suggestion sounds a lot more implement-able so far.
Later,
j
Reply to
operator jay
The setup I described measures winding current.
One could also throw a turn around any section of the core and measure voltage. Multiply the two and get power. Both measurements could be made on a section of the core lying between the primary and secondary windings, satisfying the OPs request to measure power transferred only using measurements made of the core.
Reply to
Paul Hovnanian P.E.

Further Reading

  • Shuns,etc. - returning this NG to sanity.

  • One advantage of the proposed shun is that the group ofprominent infantile...

  • I haven't been on this NG for years

  • It seems to have gone to hell.PLC programming anyone? I'd like to change...

  • What's happened to this NG?

  • Hi, I just wondered what happened to this NG? Used to be a lot of commenting,...

  • Are standards important in this NG?

  • This NG is used to field many questions upon the subject ofElectrical...

  • What is the point of this NG?

  • Is it really an electrically-oriented group or is this just another...

  • Looking for a plexiglass dome

  • I got one about 12" diameter from Edmund Scientific a couple of years ago.I...

  • testing this NG

  • I think Dan was in for some "renovations". There are a couple ofpathetic little...

  • Twenty-two years ago

  • In 1990, I owned a welding company. A homeowner's association called me to...

  • Derivation Of The Spectrum Due To f(t).d(t - T)?????

  • This NG is an international public forumwherein one expects to see technical...

  • 15 Years ago....

  • Mr M Perman was taking the editor of 'Old Glory' magazine to task over...

  • This job leaves me perplexed; it's from 20 years ago

  • The die makers put a punch on a steel plate. They then put keys butted up next...

  • What kind of rod is this?

  • I just bought some assorted welding rod at an auction (a local machine/fab shop...

  • what kind of propane torch is this?

  • This is a weird Bernzomatic handheld propane torch. Screws onto a bottle. It has...

  • moderate or dissolve this NG ??

  • In looking at the (lack of) content, the spamming, nutcase postings, bleachbot...

  • Listing this NG in the Wikipedia

  • Hi, Brian. Hey, gang.Doing better with a lot of help to get there. I'm...

  • Battery Charger Blues

  • I made the mistake of buying a Chinese-made battery-operated electric drill,...
  • « previous thread

  • circuit breakers?

  • Hey guys, Got a question about circuit breakers, I have a HarbourFreight stick...
  • next thread »

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.