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Dave Martindale Dave Martindale is offline
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Default Magnetic vs electronic transformer?

Don Wiss writes:

MAGNETIC TRANSFORMERS operate at standard low frequencies (5O/6O Hz). They
offer very reliable operation and are very durable, Since magnetic
transformers operate at low frequencies, they experience much less vo1tage
drop over a long distance compared to high frequency electronic
transformers. For optimum performance, all our magnetic transformers must
be loaded to a minimum of 80% of the transformers maximum output wattage.
For example, a 300W transformer must be loaded to a minimum of 240W in
order for the output voltage to be equal to or less than 12VAC. Otherwise
the output voltage will be greater than 12VAC and cause lamps to burn out
prematurely. All Fusion magnetic transformers are designed to carry a full
load.


Hmm. This says that the transformers have relatively poor regulation
due to high internal resistance, so output voltage drops with load, and
that they have compensated for this by making the open-circuit output
voltage higher. This probably does give the smallest, least expensive
transformer for a specific load that the transformer is matched to.
But the transformer is likely to run hot at that load.

I wonder if there are other suppliers that sell lighting transformers
whose open circuit voltage is just 12 V, with better regulation so the
output voltage falls less with increasing load. Such a transformer
could be used for any load, from a single lamp up to full rated output.
It would run cooler too, with lower losses at full load. But it will be
larger (larger diameter copper, or fewer turns of copper which requires
more iron) than the transformer with poorer regulation.

Dave