I hate to contradict you, Ship, but regardless of whether the
dimmer is limited in "soft patch" or by simply telling people not to go above 50%, the maximum wattage of all lamps on a single
dimmer should never exceed the rated wattage of the
dimmer. It is NOT "safe." As a matter of fact, if dimmed to 50% (either at the
fader or by "soft patch"), the triacs or SCRs in the
dimmer are under greater stress for a given lamp load than if they are operated at 100%.
A.C.
Line current is a
sine wave, going from zero to maximum positive
voltage, back to zero, then to maximum negative
voltage and back to zero for each full cycle. The
dimmer controls
power going into a lamp by turning the
thyristor (the general class of semiconductors that includes both triacs and SCRs) on part way through each half-cycle (it turns off automatically when the
voltage gets back to zero). But a
thyristor doesn't turn on instantly - it may take several microseconds to go from completely off to completely on.
Power is volts times amps. When the
thyristor is completely off, the full
voltage of the
power line is across it, but there's no
current, so no
power is being turned into heat in the
thyristor. When it is completely on, the
current flowing through it is at its maximum, but the
voltage across the
thyristor junction is very low, so there's almost no
power. It's only during the turn-on time that any appreciable
power is turned into heat within the device. As the
thyristor turns on,
current increases and the
voltage drops - at some
point the
thyristor sees half the
voltage and half the
current, and for that brief instant is turning a lot of
power into heat.
When the
dimmer is set to 50%, the
thyristor is turning on halfway through each half-cycle, just at the
point when the
voltage is at either the positive or negative maximum: the
point where there will be the greatest amount of
power converted to heat during the turn-on time.
When the
dimmer is set to 100%, the
thyristor is turned on all the time. While
current will be at its maximum, almost all the
voltage is across the lamps, almost none across the
thyristor, so almost none of the
power is converted to heat in the chip- most of it gets to the lamps.
John