| phil-news-nospam@ipal.net 2008-03-26, 9:25 am |
| On Wed, 26 Mar 2008 06:32:38 -0700 (PDT) VIDHYA <vidhya36@gmail.com> wrote:
| both 3phase induction motor and transformer are working on the same
| principle of em induction only , in motor alone why rmf is produced
| why not in transformer?
The transformer is rigid with respect to both windings. When there is
no current in the secondary, the magnetic field produced by the primary
is limited by the primary inductance (and some slight resistance). When
current flows in the secondary as a result of the voltage induced on it
by the field in the transformer core, that current effectively reduces
the field (since current in that direction on the secondary produces its
own field of the opposite polarity). Now that the field is reduced, more
current can flow in the primary. This will level out at whatever current
is needed to supply power to the load attached to the secondary.
A motor will have current flowing in a winding that is nearby to a magnet
or magnetic field oriented so it will attract or repel. This creates the
mechanical force that can result in motion. The windings of a transformer
are wound close together and are concentric with each other (even if on
opposing sides of the core). There is some residual mechanical force on
a transformer, but it is very small. The hum of a transformer is not from
that force, but rather, it is from the constrictive effects the alternating
field has on the core itself.
--
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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