From: dhky@shaw.ca   
      
   On 24/09/2014 4:30 AM, tctomcosby@hotmail.com wrote:   
   >   
   >   
   > Tomtech, I will try to contact you if time permits. You cannot on one   
   > hand state that "leakage Flux" whatever you think it means has no   
   > role in the power transfer process, and on the other hand state the   
   > poynting vector is correct view. I do not know the problem you are   
   > having with H flux? IT IS FLUX, formed in the air spaces, due to the   
   > MMF from winding current, either primary or secondary. Perhaps what   
   > we have is a semantics problem. IF you do not think H flux is real,   
   > remove the core from an energized transformer, A SMALL ONE, LIKE A   
   > DOOR BELL TRANSFORMER. Yeah the exciting current will go thru the   
   > roof, BUT a back EMF will still be produced and the same "FLUX" will   
   > form, but NO CORE to form in, only the air.   
      
   I have clipped the Billyfish part as there is no point repeating it.   
      
   However, the problem above goes beyond semantics. We typically speak of   
     flux  as phi- webers  and B as flux density. This is analogous of   
   speaking of current and current in a conductor. In this case, one can   
   consider H as equivalent to E  -i.e. the integral of H.dL around a path   
   (closed)is analogous to the V applied to a circuit =the integral of E   
   around the path (closed).   
      
   Maxwell /Faraday Integral of E.dl around a closed loop = -integral of   
   (-dB/dt) .dA  which comes down to Voltage (applied -ignoring series   
   drops- or back EMF -in either case a generated voltage ) is determined   
   by -d(phi)/dt   
      
   One can go from this to Vave (half wave average=4fNA(Bmax) for a   
   symmetrical waveform. If a sine wave multiply by 1.11. to get rms.   
      
   The result of this is that there is a direct relationship between   
   induced voltage and the flux (phi) or flux density which doesn't involve   
   the path length or material (B will depend on cross sectional area). You   
   have correctly said that.   
   Now, you have correctly said that the exciting current goes up   
   drastically. That means the total NI and the H must be higher--why?   
   longer path and lower mu. In the AC case it is the flux (phi =B*A) that   
   with consideration of materials etc, the magnetizing current and H.   
      
   Yes- in the DC case, it is the current that determines H and the   
   corresponding B but there is no induced voltage-but in the AC case it is   
   the opposite( one can induce a DC voltage with a steady current ramp but   
   only for a short time before magic smoke appears.   
      
   >I am not trying to say   
   > the core flux is not important, only that the ENERGY does not travel   
   > thru the iron core from one winding to another via the B flux in the   
   > core. If core flux did transfer the energy it would, by one working   
   > definition of REAL power, have to be in phase with the primary   
   > voltage, it is lagging 90 degrees...   
      
   Please note that H for an unloaded transformer, is determined by the   
   core flux. load the transformer and as the primary voltage is fixed,   
   ignoring series losses and leakage reactances, NI total =NIprimary(+in)   
   -NI secondary(+out) =NI magnetizing- which doesn't change in phase or   
   magnitude so isn't involved in power transfer.\   
   Note that for the core flux lagging the primary voltage by 90 degrees,   
   with respect to the primary voltage- the induced secondary voltage is   
   also in quadrature with the core flux. In fact, with a secondary load of   
   any phase, there appears, on the primary a load that has the same phase.   
   The transformer acts in a manner equivalent to a gear or a lever.   
      
   No nonsense at all, the other   
   > item probably hard to see is that the Leakage flux DOES NOT have to   
   > LINK with the secondary to transfer power.I agree, some of the   
   > leakage flux does not participate in power transfer, only to act as a   
   > choke.   
      
   None of the leakage flux is involved in power transfer.   
      
   Standard practice for transformer builders used to be to short   
   > the secondary and gradually apply voltage to the primary until the   
   > rated secondary current is reached. Percent impedance used to be   
   > stamped on power and distribution transformers.   
      
   Yep -done it many times (and know the approximations involved) Combine   
   this with an open circuit test (apprximations known)and you have the   
   basis of a complete "standard" model including the data needed to   
   correct the approximations If one has better facilities, then back to   
   back tests may give better information.   
   Nothing that I have said is not in the literature readily available.   
   Just remember V<-->B and H<--->I magnetizing   
      
     At you request,   
   > because our discussion has run on, and I would like to hear and learn   
   > more from you, I will try to e-mail or at least clean up my posts as   
   > to make them readable....Thanks...   
   >   
   Your posts are OK, the problem may be at my end and curable by simply   
   telling Thunderbird to rewrap.   
      
   --   
   Don Kelly   
   remove the cross to reply   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)