Spehro Pefhany, You are clearly well educated, however, I have an entirely different view of the situation. I do not consider resistors to be surge protectors. A 1,600 V inductive spike will have a DVDT that can not be suppressed by any RC circuit. If I was trying to implement surge protection I would employ an appropriate surge protector such as a Raychem over current surge protector. In my view, we are trying to get as much electrical current as possible from a high voltage source. As we are trying to "get" current, we don't want to "limit" the current whatsoever as that becomes counter productive, is inefficient and generates heat. In my view we want the impedance as low as possible. Voltage transients due to current in rushes are proportional to the resistance (impedance) of the circuit so that a higher resistance (impedance) will contribute to a higher transient voltage (I x R or I x Z). The majority of power line transients are due to "inductive" (not capacitive) voltage spikes caused by the collapsing electromagnetic fields of inductors which have experienced a removal of power. The power line's ability to kill equipment occurs when a motor or solenoid is deactivated at the moment of peak line voltage resulting in an inductive spike that is 7.07 times greater than the line voltage. The second most problematic source of voltage transients is from arching and ring oscillation in power switches and relay contacts which generates bursts of pulses with on times approaching RF frequencies. The switches and relay contacts also contribute to inductive voltage spikes of the inductive apparatus on their circuits. Turning off inductive equipment causes transients not turning inductive equipment on. As for power factor, the capacitive current of 150 mA in this application or a few amps in my applications is not of any significance to the utility companies local distribution transformer with a 10,000 amp capability. It should also be noted that if there was the introduction of a massive capacitive load to the power line that the line voltage would actually dip due to the current demand. The notion that capacitors are frail and can not withstand power line behavior is unsubstantiated. Capacitors have been used for decades as filters in equipment and directly connected across the power line. Utility companies employ capacitors for filtering and power factor compensation directly to the power lines. Selection of the proper composition of capacitor with a conservative voltage rating will assure reliability in conjunction with the power lines. For maximum reliability the capacitor should be rated for the electrical environment and not for just the working voltage. Excluding lightning strikes, when capacitors fail it is because the electrical environment exceeded the capacitor's rating. It should also be noted that a capacitor with a 2kV rating will absolutely not be harmed by the maximum inductive spike of 1,600 V produced on a 220 Vac power line. Of course lightning strikes require spark gap and/or MOV technology and there are no absolute assurances with lightning. I really honestly believe that Vasile should be commended for his circuit and encouraged. Sincerely, Ned Seith Nedtronics 59 3rd Street Gilroy, CA 95020 (408) 842-0858 G O T G A R L I C ? GILROY GARLIC FESTIVAL 2001 STARTS TODAY! At 09:39 AM 7/27/01 -0400, you wrote: >At 05:46 AM 7/27/01 -0700, you wrote: > > >I would not add a resistor in series with the capacitor (C9) as this will > >vary the effective capacitance reactance which is providing the desirable > >voltage drop and will also dissipate heat. > >It is the only thing limiting current when voltage transients appear at >the input (as at turn-on). All production circuits will include this >resistor. >Consider the surge current rating on the metal film capacitor if nothing >else... >the current at switch-on is otherwise limited only by the impedance of >the mains and the connections to the capacitor, which can blow the >thin metalization right off the dielectric, creating holes and eventual >failure ('self healing' notwithstanding). Needless to say, it also >whacks the diodes with a surge, though diodes are fairly tough, I don't >like to see the circuit dependent on external factors (such as whether >the customer has plugged it into an extension cord or not) to be reliable. > > >I would not be too concerned with the capacitor (C9) remaining charged as > >the approximate 6 mA current consumption from the voltage regulator will > >quickly discharge the capacitor. UL and TUV stipulate that the voltage > >potential on an unplugged power cord must diminish to 1/3 of the mains > >voltage within 10 seconds. So, If I wanted to increase the rate at which > >the capacitor discharges, I would place a resistor in parallel to (C5) on > >the low voltage side of the circuit. > >This will do nothing- the capacitor is in series with the low voltage >side when the plug is removed from the socket and the voltage will remain >too long to meet any kind of safety standards without a parallel resistor. >You won't see an approved design without it, or some equivalent. > > >I would want a 1/4 amp fuse between the 220 Vac main and the series > >capacitor (C9). > >A flameproof fusible resistor can probably be used to avoid the need for >that... >it has to be a high surge current type anyway (not metal film, but MOF >or wirewound). > > >I would also want the series capacitor (C9) rated for 800 V to 1000 V. > >Preferably with an AC rating > maximum line voltage. > > >If the series capacitor (C9) is getting warm at all, then the voltage > >rating should be increased. > >Yes, a film cap should never get warm. > >Have you gotten your "several amperes" supplies inspected by any >safety approval agencies? Are there any power factor specifications >that cause problems? > >Best regards, >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= >Spehro Pefhany --"it's the network..." "The Journey is the reward" >speff@interlog.com Info for manufacturers: http://www.trexon.com >Embedded software/hardware/analog Info for designers: http://www.speff.com >Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= > >-- >http://www.piclist.com hint: The list server can filter out subtopics >(like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics