I can think of only two way to reduce flicker, provide the control you need, and keep harmonics low.
The first you already mentioned - a "power factor corrector" (really a harmonic corrector that also corrects power factor at the same time). What you need should be quite a bit less expensive than a typical power factor corrected switching power supply. You need no more than the power factor correction circuitry, with power flow controlled by heat demand rather than the need to maintain voltage on an energy storage capacitor (as in a switching power supply). The design is a bit different, but not greatly so. The other solution would be to have several heater elements and switch them carefully. For example, if you presently have a 1500 watt heater, you might be able to break it up into a 500 watt heater and a 1000 watt heater. The switching would be done so that there was never more than a 500 watt change at any time. For example, when the device is first switched on, it would not start immediately at 1500 watts, but would start at 500 watts, switch to 1000 watts, and then switch to 1500 watts. These smaller steps, properly timed, might be enough to pass the flicker standard. NOTE: I have not done any analysis to prove that this would meet the flicker standard. The only other thing that comes to mind is a circuit with a power transistor. The circuit makes the power transistor look like a controllable resistor, and the transistor is the heater. Well, it was just a thought..... Don Borowski Schweitzer Engineering Labs Pullman, WA, USA "Eurtronik Studioerre" <studioe...@eurtronik.it>@majordomo.ieee.org on 03/14/2003 02:45:27 AM Please respond to "Eurtronik Studioerre" <studioe...@eurtronik.it> Sent by: owner-emc-p...@majordomo.ieee.org To: <emc-p...@majordomo.ieee.org> cc: Subject: flicker & harmonics currents reduction Hi, does anybody know a way to reduce flickering & harmonics currents in order to meet EN 61000-3-2 EN 61000-3-3 in consumer electronics products? Especially, I have a steam cleaning machine with phase-cut power control (similar to light dimmers) that doesn't want to meet the two standards together. The phase-cut control gives a lot of problems in harmonic currents, but goes well for the flicker. On the other hand, switching the power on and off in a slow (seconds) duty cycle, goes well for the harmonic currents limits, but it creates an hard flicker problem! I know that introducing a Power Factor Corrector circuit helps so much in harmonic currents reduction, but this is very expensive.... Many thanks for your help, Federico Quadri emc lab test engineer Eurtronik Studioerre Srl Via Andrea Costa, 35 40013 Castelmaggiore (BO) - Italy T +39-051-703284 F +39-051-700904 e-mail studioe...@eurtronik.it This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
