I'm looking for some MR16 recessed swivel lamps. For installation in an existing ceiling a shallow remodel housing for remote transformer makes for the easiest install. But do I want a magnetic or electronic transformer? I don't plan to dim.
Don (e-mail link at home page bottom).
As long as you don't plan to dim, I'd get whatever is cheaper. Magnetic is going to be heavier
I found this:
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.
ELECTRONIC TRANSFORMERS are very compact and much smaller than their magnetic counterparts. They provide built in protection against electrical shorts applied at the outputs and to the lighting system, In order for electronic transformers to operate properly, the output must be loaded to a minimum of 50% of the rated wattage of the transformer. Any output load below 50% may result in lamps flickering and premature lamps burning out. Since electronic transformers operate at much higher frequencies, most standard volt and amp meters intended for 6Ohz type measurements cannot be used to accurately measure the outputs of these transformers. To measure the output, we recommend using a Fluke digital multimeter model number 189.
Electronic transformers may cause interference with appliances such as TVs and radios. If interference is a problem, a line filter may be installed either at the transformer or at the appliance input, Another option is to use a magnetic transformer, which operates at a lower frequency and will not cause any interference.
Don (e-mail link at home page bottom).
As the transformer will be in a nearby closet the weight isn't of concern. What is of concern is the load. I figure I will have five MR16s 32" apart. I don't know just what wattage. My ceilings are 11 1/2'. I plan to wall wash. I find 150w and 300w transformers. As you can see from my other post each type has a different minimum load. If I go for 42w bulbs, the 210w total is too low for a 300w magnetic transformer. But the electronic has interference issues and at 15' for the furthest I would have to use really heavy wire to not have a voltage drop.
Don (e-mail link at home page bottom).
If these things are the same as ballasts for flourescent lights, go with electronic bought from an electrical supply place, not Home Cheapo. They don't buzz or hum and they run cool.
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
On 4/7/2008 1:02 PM Dave Martindale spake thus:
[...]
Regulation, schmegulation.
I wouldn't sweat that part of the equation; this is far from a high-precision system, and a little variation, or even fluctuation, of voltage isn't going to make any perceptible difference. The load, after all, will be fixed, once the O.P. gets all the lamps installed, so a common ordinary transformer will work just fine here.
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