PelleS:
Thank you for the info. Do you know how dimmers can work with both Incandescent and Halogen lights and still be wired the same way? I have a dimmer here where it says it works with both.
This is the most mind-bending discussion I have seen here for some time!
A Halogen lamp with a transformer is essentially a resistive load. The only inductance of concern is the leakage inductance of the transformer. The common series-wired two wire dimmer does not even notice the difference. A microprocessor-controlled phase controlled dimmer should work just as well.
If however you have halogen down-lights, the best thing is to replace them with LED luminaires - much more efficient means less heating; you can get dimmable ones which will work just fine with phase dimming if they are so specified.
A zero-crossing optocoupler such as the MOC3041 completely prevents phase control for dimming.