IGBT Dimmers

"Guy Macon"

** Incandescent lamps in the " 10-100kW range " are rare beasts indeed.

You sure about wanting single channel dimming at such huge power levels ?

** IGBTS are used in two quite separate ways as dimmers - as you first URL alludes to.

1. Phase control by chopping the AC wave.
2. PWM of the AC wave to produce sine wave output at lower voltages.

** The issue with phase control is that the fast switching of large currents generates EMI - particularly bad in the audio and AM broadcast bands. Choke filtering helps with the AM band noise - but annoying buzz injection into audio systems is still there.

With IGBTs, the turn on and off times can be controlled to reduce ( AM band) EMI, plus the chopping of the AC wave normally operates in the reverse sense - ie starting at zero volts, rising slowly with the AC input voltage and cutting off as required.

With PWM sine wave dimming, EMI can be virtually eliminated making these dimmers very suitable for use in close proximity to sensitive audio gear. Sine wave dimmers cause no harmonic current in the neutral and have unity power factor - but cost a lot more to make than the simple phase control types.

Phase control dimmers, of whatever type, DO cause harmonic currents and have poor power factors - despite the false claims being made in some of the URLs you posted.

But they *are* cheap.

........ Phil

Who would need a dimmer for a lighthouse? Isn't that self-defeating?

Here's one that you missed, which might be of interest:

It has several ouput modules including IGBT.

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John B

Just because you haven't prsonally worked with Incandescent fixtures that draw more than 10kW of power, tha doesn't mean that they don't exist. For example:

20kW Fresnel light 145kW Super Wendy light (224 bulbs x 650W = 145.6kW)

In addition, common usage of the the term "dimmer" referes to a device that reduces the wattage of AC power, and does not specify the load (although if the load isn't resistive, that should be mentioned). A nickel-chromium resistance wire heating element can also be dimmed. In such a case the load is still incandescent, with the output mostly infrared and with with a small amount of the output in the visible red.

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Guy Macon

Thanks! I found a lot mor by doing a Google search on "Open Dimmer":

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Guy Macon