Burn out 120V lamp on 120V circuit?
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From: VWWall on 5 Aug 2010 14:03 A while back, in another Usenet ng, someone asked about using an ordinary 120V incandescent lamp to slow down a fan motor. A number of posters replied that they had successfully done this. The usual discussion of the merits of doing this ensued. Then, one frequent poster replied that he had tried this with a small AC motor, and the 120V bulb, in series with the motor, burned out when the circuit was completed. There was much discussion, with many saying that it was impossible for any two terminal passive device in series with a 120V incandescent bulb on a 120V circuit to cause that bulb to burn out. Some even set up Spice simulations which were difficult because of the large variation in the bulb's resistance from cold to fully "on". The OP was asked to repeat the experiment, which he did several times, with the same results of the bulb burning out. The final conclusion, perhaps not shared by all, was that it was possible for a passive device to act in this way. One poster even showed Spice results with an increase in line current due to motor inductance. It was never proved that this increase was enough to cause the bulb to fail. I haven't tried the experiment myself, since I don't have a suitable small motor available, and with 120V incandescent bulbs on the endangered species list, I don't care to sacrifice even one! Some time ago, I did use a series 120V 100W bulb to slow down the compressor fan motor in my refrigerator, when the proper replacement was not available. I have my own theory and can postulate a two terminal passive device capable of behaving in this way. (It doesn't even need pre-"charged" condensers.) What say ye all? -- Virg Wall, P.E.
From: Jim Thompson on 5 Aug 2010 14:27 On Thu, 05 Aug 2010 11:03:28 -0700, VWWall <vwall(a)large.invalid> wrote: >A while back, in another Usenet ng, someone asked about using an >ordinary 120V incandescent lamp to slow down a fan motor. A number of >posters replied that they had successfully done this. The usual >discussion of the merits of doing this ensued. > >Then, one frequent poster replied that he had tried this with a small AC >motor, and the 120V bulb, in series with the motor, burned out when the >circuit was completed. > >There was much discussion, with many saying that it was impossible for >any two terminal passive device in series with a 120V incandescent bulb >on a 120V circuit to cause that bulb to burn out. > >Some even set up Spice simulations which were difficult because of the >large variation in the bulb's resistance from cold to fully "on". The >OP was asked to repeat the experiment, which he did several times, with >the same results of the bulb burning out. > >The final conclusion, perhaps not shared by all, was that it was >possible for a passive device to act in this way. One poster even >showed Spice results with an increase in line current due to motor >inductance. It was never proved that this increase was enough to cause >the bulb to fail. > >I haven't tried the experiment myself, since I don't have a suitable >small motor available, and with 120V incandescent bulbs on the >endangered species list, I don't care to sacrifice even one! Some time >ago, I did use a series 120V 100W bulb to slow down the compressor fan >motor in my refrigerator, when the proper replacement was not available. > >I have my own theory and can postulate a two terminal passive device >capable of behaving in this way. (It doesn't even need pre-"charged" >condensers.) > >What say ye all? Having burned myself seriously as a kid, using an Erector Set motor winding to blow flashbulbs (�), I can assure you that a bouncing contact will do it ;-) (�) The flashbulb (Press 25) melted over my finger :-( ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: VWWall on 5 Aug 2010 15:02 Jim Thompson wrote: > On Thu, 05 Aug 2010 11:03:28 -0700, VWWall <vwall(a)large.invalid> > wrote: > <snip> >> The final conclusion, perhaps not shared by all, was that it was >> possible for a passive device to act in this way. One poster even >> showed Spice results with an increase in line current due to motor >> inductance. It was never proved that this increase was enough to cause >> the bulb to fail. >> <snip> >> I have my own theory and can postulate a two terminal passive device >> capable of behaving in this way. (It doesn't even need pre-"charged" >> condensers.) >> >> What say ye all? > > Having burned myself seriously as a kid, using an Erector Set motor > winding to blow flashbulbs (�), I can assure you that a bouncing > contact will do it ;-) > > (�) The flashbulb (Press 25) melted over my finger :-( > > ...Jim Thompson Not quite the same thing. I have had #25 flash bulbs go off in my pocket from EMF radiated by trolley lines. An ordinary incandescent bulb requires much more energy to cause its filament to burn out. -- Virg Wall, P.E. (Correct signature delimiter is "-- CR", i.e. "--(space)CR"...)
From: Jim Thompson on 5 Aug 2010 15:07 On Thu, 05 Aug 2010 12:02:27 -0700, VWWall <vwall(a)large.invalid> wrote: >Jim Thompson wrote: >> On Thu, 05 Aug 2010 11:03:28 -0700, VWWall <vwall(a)large.invalid> >> wrote: >> ><snip> >>> The final conclusion, perhaps not shared by all, was that it was >>> possible for a passive device to act in this way. One poster even >>> showed Spice results with an increase in line current due to motor >>> inductance. It was never proved that this increase was enough to cause >>> the bulb to fail. >>> ><snip> >>> I have my own theory and can postulate a two terminal passive device >>> capable of behaving in this way. (It doesn't even need pre-"charged" >>> condensers.) >>> >>> What say ye all? >> >> Having burned myself seriously as a kid, using an Erector Set motor >> winding to blow flashbulbs (�), I can assure you that a bouncing >> contact will do it ;-) >> >> (�) The flashbulb (Press 25) melted over my finger :-( >> >> ...Jim Thompson > >Not quite the same thing. I have had #25 flash bulbs go off in my >pocket from EMF radiated by trolley lines. An ordinary incandescent >bulb requires much more energy to cause its filament to burn out. I don't know. Is charge conserved ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: Joerg on 5 Aug 2010 16:18
Jim Thompson wrote: > On Thu, 05 Aug 2010 12:02:27 -0700, VWWall <vwall(a)large.invalid> > wrote: > >> Jim Thompson wrote: >>> On Thu, 05 Aug 2010 11:03:28 -0700, VWWall <vwall(a)large.invalid> >>> wrote: >>> >> <snip> >>>> The final conclusion, perhaps not shared by all, was that it was >>>> possible for a passive device to act in this way. One poster even >>>> showed Spice results with an increase in line current due to motor >>>> inductance. It was never proved that this increase was enough to cause >>>> the bulb to fail. >>>> >> <snip> >>>> I have my own theory and can postulate a two terminal passive device >>>> capable of behaving in this way. (It doesn't even need pre-"charged" >>>> condensers.) >>>> >>>> What say ye all? >>> Having burned myself seriously as a kid, using an Erector Set motor >>> winding to blow flashbulbs (†), I can assure you that a bouncing >>> contact will do it ;-) >>> >>> (†) The flashbulb (Press 25) melted over my finger :-( >>> >>> ...Jim Thompson >> Not quite the same thing. I have had #25 flash bulbs go off in my >> pocket from EMF radiated by trolley lines. An ordinary incandescent >> bulb requires much more energy to cause its filament to burn out. > > I don't know. Is charge conserved ?:-) > Nowadays charge doesn't need to be conserved anymore, that's so yesterday. You just print new charge. And if that ain't enough you borrow some charge. If that still isn't enough you go into closed-door meetings with some bankers and leverage the leverage, a derivative scheme that can make 15 charges out of one real charge. Some folks on the hills are also quite good at that. Plus the bankers will make all the charge that had gone bad over the years look like new charge and repackage it for ya, with AAA rating and all the trimmings. Of course, the one real charge you walked in with will be required as a fee, so the proper charge bonus can be paid out later. Not to you, of course ... -- SCNR, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |