Dimmer for American Loads on Europe

Since I often travel between Europe and America I have a number of work appliances that are AC 110V, fed here in Europe using a high power phase dimmer. These are resistive or have small universal motors.

I'm happy functionality wise (in fact I can even regulate power as a bonus), but I was looking for a smarter way to accomplish this that would be easier on the EMI, after all, I'm suddenly switching 10 or 20A to a resistive element at some point in the sine wave and I had this causing issues on some places.

I know using an inductor to limit DI/DV would be ideal, but this adds unnecessary weight and the idea is for the converter to be portable (as in carry on luggage portable)

I have pondered skipping cycles. So have 230V directly on the element (4x rated power) for one full cycle (20mS) and then skipping 3 cycles (60mS), but not sure how to trigger the triac for exactly one cycle (otherwise, if starting half way, the same problem as above would remain).
PWM'ing the sine wave using high frequency IGBT/MOSFET with an input filter capacitor/suppressor coil could also work, but I'm concerned with excessive power dissipation/circuit complexity

Any thoughts on this?

turning on at the zero crossing and then turning off at the mains peak (or 5ms later) will give ~ 115Vrms from 230Vrms supply, also much less RFI, 2 x IGBT emitter coupled needed.

Hi,

turning on at the zero crossing and then turning off at the mains peak (or 5ms later) will give ~ 115Vrms from 230Vrms supply,

Click to expand...

No, this gives about 162V RMS....at least when you do this for both polarities.

230V, ON at 0°, OFF at 90°, ON at 180°, OFF at 270°, gives: 162V RMS, but 115 V rectified average, 0V not_rectified average
230V, ON at 0°, OFF at 90°, not ON at 180°, gives 115V RMS, but 57 V rectified average, 57V not_rectified average

Klaus

sorry, turning off at peak mains, 90deg, same for neg 1/2 cycle will have exactly half the heating effect of full 230Vac, hence I thought 1/2 Vrms

whereas 70deg turn off will give, apparently ~115Vac rms, which seems counter intuitive, even though half V on the same load gives 1/4 power

Hi,

sorry, turning off at peak mains, 90deg, same for neg 1/2 cycle will have exactly half the heating effect of full 230Vac, hence I thought 1/2 Vrms

Click to expand...

Turning OFF at 90° and 270° give 50% of the duty. Correct.
It gives 50% of the heating power. Correct.

But since P = I^2 × R --> V_RMS = sqrt(0.5) of V_RMS_fullwave
V_RMS = 0.707 × 230V = 162V.
***

1/2 V_RMS results in 1/4 power.

Klaus

KlausST said:

Hi,



Turning OFF at 90° and 270° give 50% of the duty. Correct.
It gives 50% of the heating power. Correct.

But since P = I^2 × R --> V_RMS = sqrt(0.5) of V_RMS_fullwave
V_RMS = 0.707 × 230V = 162V.
***

1/2 V_RMS results in 1/4 power.

Klaus

Click to expand...

Correct, which is the nominal power rating, since the devices are 115VAC to start with. This is how I'm currently implementing it, but has the issue observed with EMI, hence I'm pondering other solutions such as PWM/or cycle skipping.

I've been reading a bit on trailing edge dimming as well. Its supposed to reduce EMI, although I'm not sure how suddenly cutting a large current flow is any better than doing the opposite (unless, of course, this is because of the large inrush caused by a cold filament when power is applied, reacting in a similar way to a capacitive load?)