Power controller for centrifugal fan
I happened upon a very useful AC power controller on eBay. The Kemo M028N power control cost about £22, which is a lot cheaper than the equivalent variac. The device can handle anything up to 4000 watts at 240V or 2000 watts at 110V. However, a heat sink and fan will have to be employed for high power devices.
The photo above shows a quick test using a light bulb. The light is dimmed to its lowest possible level. Now, I need to rewire my centrifugal fan to handle AC again, after converting it to DC a few weeks ago. At last I have a controlable fan. No more excuses to avoid completing my downdraught gasifier.