ECN Forum Forums Technical Discussion Electrical Theory and Applications Dimmer Switch

I'll take a shot at this

1: A full wave dimmer would use a Triac, as opposed to a single SCR. This would work on both waves of a circuit [the waves of both flow directions].
A full wave bridge device would work on both waves [directions] and on each wave above and below the center line [similar to a full wave bridge rectifier]. It too, would use Triacs if the lamp was to continue receiving AC, or 4 separate SCRs, if the lamp could use DC.
A Half wave device [dimmer] would use an SCR and only control one wave, or flow direction, and only the part above the zero line.

2: Time rise would be the time it takes for the "triggor" circuitry to switch on the Triac, or the SCR. Could also relate to the minimum amount of dimming [the smallest wave that can pass the Thyristor {Thyristor is an SCR, Triac or Diac}].
Overshoot is spike level, or maximum voltage that can be seen at either the triggor circuit, or the thyristor. Peak is the level on either the wave above, or below the zero line, to the fullest amplitude of the wave [the peak part of the wave].
Typical voltage meaurements are done using the RMS value of the wave, which is 0.707 of the peak value. When you say your house has a 120 Volt circuit, you are referring to the RMS voltage.
Diodes [LEDs, SCRs, Triacs, etc] see the entire wave at all points, so they are rated for peak values [typically peak inverse voltage].
Rectifiers use the average value, which is 0.63 of the peak value.

3: Ghost load is either the minimum, or maximum Resistance connected to the output of the dimmer. This would be the Incandescent lamps that are being dimmed.
Ghost load is a value between a low and high limit that will determine how much current will flow with the dimmer set for the lowest dimming setting available before the thyristor ceases to conduct.
If you have seen dimmers with LED indicators on it, these use the "Ghost Load" of the connected lamps to connect the AC power to them. There cannot be too little of Resistance [like using more than a total of 300 watts worth of lamps], nor can there be too high of Resistance [like using only one 5 watt lamp].
That determines the level of current that can flow outside the dimmer [in a round about way ].

If you have absolutely no idea of what I am talking about here , please reply and maybe with help from others in the group, I can explain these things!

Scott SET