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Re: microwave trans



Subject: 
            Re: microwave trans
       Date: 
            Thu, 27 Mar 1997 09:02:20 +1200
       From: 
            "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: 
            Wellington Polytechnic, NZ
         To: 
            tesla-at-pupman-dot-com


Hi all,
        Having measured primary currents and motitored waveforms on 
these things, I offer the following:
    Calculating power dissipation in the house supply when 
paralleling these things up is completely unrealistic if you base it 
on RMS values. A single transformer has a terrible form-factor and 
generated current waveforms like this:
      **
     *  *
    *    *    
   *      *
*            *           *
                *     *
                 *   *
                  * *
                   *
with current peaks hitting around 18A  (230V supply). Two paralleled 
gave the variac a real workout. A TC cap across the secondary made no 
sybstabtial difference to the primary current either. These peaks 
will be causing I^2R heating in any poor connections in the household 
wiring while the transformer is drawing little real power due to the 
phase difference between current and voltage.

Malcolm