Volts, amps and electric power supplies/components

[terry.shitcrumbs]

Hello All.

Is it at all useful (or accurate) to think of volts as being "pushed" aroun d a circuit by the power supply and amps as being "drawn" by the components fed by it? In other words, is it right to work on the assumption that a po wer supply that exceeds the voltage rating of the components its feeds migh t damage them, but will probably not get damaged itself. Conversely, workin g on the assumption that a power supply whose maximum amperage rating is be low that of the components its feeds might itself get damaged, but that the components will not.

Is that broadly correct, or have I got the wrong end of the stick?

Thanks. Terry.

[harry]

und a circuit by the power supply and amps as being "drawn" by the componen ts fed by it? In other words, is it right to work on the assumption that a power supply that exceeds the voltage rating of the components its feeds mi ght damage them, but will probably not get damaged itself. Conversely, work ing on the assumption that a power supply whose maximum amperage rating is below that of the components its feeds might itself get damaged, but that t he components will not.

Think of an analogy to water in a hosepipe. The pressure is equivalent to Volts. The amps is equivalent to the amount of water moved.

Too high a pressure will force too much water through and destroy/damage th e equipment. Simple explanation here.

[Tim Watts]

The effects of damage are generally correct, but here's another analogy:

Water: Pressure = Volts and Flow (rate) = Amps.

The only failure there is an under powered pump will not die feeding a circuit that requires more flow.

[Ranger]

It's more useful to think of the volts as the pusher, and the amps as the result the pusher gets when pushing against the resistance.

Yes, but not for the reason you propose.

Yes.

Yes, but you don't need your original for the later quite accurate scenarios.

Not on the last two, just the first one.

[Brian-Gaff]

I think one of the problems whe we talk about AC equipment is that the volts measured are often not the peak at plus or minus, but the average. as i found out quite early on, if your mains is nominally 220volts at 50 hertz, even a capacitor rated at 230v can just get blown up.

I was building a mains filter at that time. Brian

[The Natural Philosopher]

??

I suppose aas a fully qualified electrical engineer I cant even believe no one else kinows this.

240V mains peaks at 415V typically. Its common to use 630V DC rated capacitors or those designed for 250V *AC*

More interesting is mains straight across an 8ohm loudspeaker...

[I love spam]

Not quite as high as 415 volts, AC voltage at 220V RMS (Root mean sqaure) will have a peak to peak voltage of +311V to -331V

(to get from RMS to peak voltage, multiply by the square root of 3)

[The Natural Philosopher]

No. Multiply by the square root of 2...

sheesh... you will be telling me next that Pi=4.

But you are nearly correct. Its about 350v peak

415v is the RMS difference between two 240V phases on 3 phase...

[pamela]

As you mentioned it, what sort of electrical qualifications do you have as an an electrical engineer. Just not sure if you mean electronics or main electrical supply.

[Bill Taylor]

Or even the square root of 2 - which you seem to have done.

[The Natural Philosopher]

Both.

[pamela]

Is that because you belong to the IEEE?

[Dave Plowman (News)]

Eh? Might have been better if you'd not given your 'credentials' first.

415v is the figure often quoted as across *two* phases of a supply. 324v is the p to p figure for a nominal 230v supply.

It would make sense to most to use a component rated for the task in hand.

Not of much interest to most. ;-)

[TomSawer]

???

This is the PEAK voltage approx not the peak to peak. Multiply 230 by root 2.

[Dave Plowman (News)]

[charles]

The I - triple E is American. The UK Institution used to be the IEE, but it changed its name to IET a few years ago.

[TomSawer]

What don't you follow?

I responded to an incorrect statement:

324v is not the peak to peak voltage of a 230v (rms) supply it is approximately the PEAK volage and there is obviously a positive and a negative peak which makes the peak to peak voltage twice this, ie. 650v.

The peak voltage is:

RMS times the square root of 2.

ie 230v*1.41421...

This is 325.2691...volts

[harry]

Drivel. As usual.

RMS value of a sine wave is 0.707 x peak value.

Average value is 0.636 x Peak value.

Different for different wave forms.

I don't suppose a janitor can be expected to know such stuff.

[Dave Plowman (News)]

You're talking bollocks...

[The Natural Philosopher]

No.