Burn out 120V lamp on 120V circuit?

Not quite. The top 10% earners pay over half (55.4% - 2006 numbers) of all federal taxes. The middle 60% pays around 30% of the federal taxes.

...unless you consider the top 10% being in the "middle". ;-)

Thank you. Another typical righteous wing lie exposed. Sad that they actually believe what their extremist conservative deities pronounce as gospel.

Paul

Which "lie" is that? The one that states that the "rich" already are slaves of the state, who pay for everything? That one, loser?

From the same document, table 1:

Top 10% have 41.6% of all pretax income and they pay 55.4% of all federal taxes. Top 1% have 18.8% of all pretax income and pay 28.3% of all federal taxes.

When the circuit's turned on the bulb filament has a lowish resistance, so a large current can build up in the inductance of the motor. Then the filament heats up, its resistance increases, and the inductor pushes the voltage up to keep the initial current flowing, with the result that the bulb filament has to handle an overcurrent for a period.

Whether this will destroy the bulb would depend critically on the characterstics of the filament and the size of the inductor.

So I'd have thought that the answer was that it's possible, but actual mileage will vary.

Sylvia.

Yes, I get it. Convince the loser and we'll have one fewer Obamanut.

I was specifically answering PeterD's assertion that the middle class pays all the taxes. No, it's far worse than that. Close to half are net receivers.

HOOT!!

The money paid by people in taxes to the government either goes back to other taxpayers (wages, purchases, and even social security, Medicare, and welfare), who spend it locally, stimulating the economy, or it goes to those who do not contribute to economic health. The only bad that results from tax and spend is a slight reduction of discretionary income for the upper tax brackets, and a net outpouring of wealth when the money finds its way into the criminal element (such as the huge drug market), and foreign powers and terrorist groups who use the money for destructive purposes. Even so-called wasteful spending still (ideally) recirculates back into the economy and promotes business growth and jobs. Tax and spend means it hurts a bit now. Borrow and spend means it's gonna hurt more later. That was the result of Bush's tax cuts. Restoring the previous structure stabilizes and perhaps reduces the debt.

Paul

That is food for thought (and thanks for replying on topic instead of getting into politics).

I don't think a very large current would build up in the motor, especially a small fan motor which is relatively self-limiting even with locked rotor. If the motor stalls, then the maximum current would be initially limited by the bulb cold filamant resistance, and the locked rotor characteristics of the motor. At worst it would be about the same as connecting the bulb to the line through a short, and since this is AC there is not a constant build-up of inductive energy. If the motor runs, then there may be some energy build up from the flywheel action of the load, but this would build very slowly in comparison to the heating of the filamant and eventual stabilization at a lower speed. The motor itself should only be able to generate the same amount of power that is involved in running at full load, which should be less than 1/8 HP or less than the 100W rating of the bulb. So even flywheel action should not be able to account for enough power being pumped into the bulb to blow it out, especially at turn-on.

Paul

No, much goes to non-tax payers.

For imported goods usually.

Which is virtually all of it.

Define 'slight'.

In this case, 'upper tax' is anyone who pays tax.

Massive foreign aid must be stopped. As well as our interference with other countries and peoples.

It hurts a lot now, and will continue ot hurt. Loss of jobs, loss of homes, inability to go to college, and so forth...

Borrow and spend is criminal. Anyone in the government who supports that should be hung by their balls until they realize just how wrong it is.

Still clueless about bush's tax cuts, eh? They brought in more income to the government, and boosted the economey. Obama's massive tax increases, coming very soon, will reduce government income and accelerate the downward slide of the current economey.

Damn it, now I'm going to have to run an experiment! Suggestions to motor specifications? Since we are talking a fan motor, maybe I'll use my shop fan, and a spare 60 watt bulb.

Absolutely clueless drivel

"Government largesse" productivity "slight reduction" - NOT! "discretionary income" "investment" It's not only the "upper income" that saves/invests

There are more real gems in there, but that's enough for now.

I think it is actually due to the inductor slowing the rate of change of current down.

I'm going to assume a simple inductor here, not a fan.

If you had just a bulb you'd get a high current initially and it will rapidly fall to steady state. So there's a peak power at the beginning but only for a very short time, this energy is absorbed easily by the element due to it's thermal heat capacity.

When you add an inductor the whole thing slows down, and instead of starting at peak power it starts at zero power. It still reaches the same steady state condition (no more rate of change of current = 0V across the inductor), but because things have slowed down by the inductor, the heat capacity doesn't come into play anymore (it already absorbed the heat early on), so there'll be a maximum steady state power that the bulb could handle before blowing and this is much lower than the normal peak power with no inductor.

This steady state maximum could, for example, be 90W for a 60W bulb.The question is therefore whether the product of the voltage and current through the bulb, i.e. the power, would ever rise above this value before falling back down to steady state. If it does peak like that then the bulb could blow before steady state is reached.

I've no idea what would really happen, but my gut feel is that the power curve could have some 2nd order, or even 3rd order, terms in it and may well have a maximum.

BTW I found this model of a tungsten lamp in case anyone wants to have a go at converting it to LTspice and simulating it:

Mark.

If this were true powering an incandescent bulb from a Variac or other variable voltage source would result in the bulb's failure before its rated voltage was reached. Photo-flood lamps are over voltaged, so it takes quite a bit of excess voltage to instantly fail the lamp.

A couple of people have tried modeling the bulb in series with an inductance. The current does rise above the expected, but not enough to fail the bulb.

Paul Hovnanian was on the right track. It's possible to conceive a two terminal device which could behave in this manner, but it would involve the storage of energy and the release of that energy in a way that would over-voltage the bulb. Any ways I could conceive involved some sort of switch, operated at a precise time.

A hint: The motor which consistently failed the bulb was a small capacitor start device. My theory may be wrong.

On Mon, 09 Aug 2010 18:12:40 -0700, VWWall wrote: [snip]

A lab-tested Spice model for a lamp...

A signficant question, to which I don't know the answer, is how long it takes a filament to approach its working temperature. If it's a short time compared with half the AC period, then the mechanism I suggested could work in the right circumstances. It it's an AC period or more, then my proposal looks rather suspect.

Sylvia.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Thanks Jim, I'll add this to my library.

Mark.

Ah, yes. That probably is not it then.

Do you know of the exact motor construction that was used? There may be a power factor issue here too, espcially if it was a switched capacitor type where the power factor could change rapidly.

Jim has kindly posted a lamp model, what we really need is a motor model with the same construction as the fan. Anyone got one?

Mark.

I already converted it, a while ago. Here's the subcircuit:

lamp.sub:

-1.642730E-14 .ends

And here's the symbol:

lamp.asy:

Version 4 SymbolType CELL LINE Normal 0 -48 0 -21 LINE Normal 0 48 0 21 LINE Normal 7 -14 0 -21 LINE Normal 1 -8 7 -14 LINE Normal 8 0 1 -8 LINE Normal 1 6 8 0 LINE Normal 8 13 1 6 LINE Normal 0 21 8 13 CIRCLE Normal 32 32 -32 -32 WINDOW 0 16 -48 Left 0 SYMATTR Prefix X SYMATTR ModelFile lamp.sub SYMATTR SpiceModel lamp PIN 0 -48 NONE 0 PINATTR PinName A PINATTR SpiceOrder 1 PIN 0 48 NONE 0 PINATTR PinName B PINATTR SpiceOrder 2 PIN -32 0 RIGHT 8 PINATTR PinName T PINATTR SpiceOrder 3