Mains transients are more likely to occur at the peak of the mains on single phase?

[treez]

..ie, rather than at the zero cross, or somewhere "off-peak".
Would you say this is accurate?

 

[barry]

No.

Don't you think it depends on WHAT'S causing the transient?

The only way you could make this assumption is due to the fact that the slope is less near the peak than at zero-crossing, so a greater part of cycle occurs near the peak rather than at zero.

 

[Nik_2213]

@T, IMHO, you're over-thinking this.
Any mains spike at the peak of the cycle is potentially more dangerous than one at zero-crossing due to it sat atop the mains wave-form.

Hence the distinction between 'voltage limiter' spike catchers and inductive components. The former dissipate voltage excursions beyond safe range, the latter block high frequency transients, regardless of phase position...

IIRC, a 'passive power conditioner' may use both, often with an LC network to divert RF components...
YMMV.

 

[treez]

thanks, as you know, a mains transient is mostly caused by a break in the current in the mains stray inductance...generally the more current that is broken , the higher the spike....and in the mains, surely most current occurs at mains peak....and least at the zero crossings.
Would you agree?

 

[KlausST]

Hi,

generally the more current that is broken , the higher the spike....and in the mains, surely most current occurs at mains peak....and least at the zero crossings.
Would you agree?

I agree with: the higher the current, the higher the spike..

But i don't agree that the most current occurs at voltage peak.
--> Without inductance, no transient.
But with inductance there is phase shift. Phase shift means, that the current peak is not at voltage peak...it is delayed...
With a pure inductive load the highest current is at voltage zero cross....
But on the other side it's not usual that there is a pure inductive load..

Klaus

 

[treez]

Thanks, also, i think we can, on most mains phases , be pretty sure that there is very little current within 1ms of the zero cross....so within 1ms of the zero cross, i would say generally that a mains transient spike is very unlikely.
I wonder if there is agreement.

- - - Updated - - -

Also, generally the broken mains stray inductive current is usually from a fuse or breaker acting, and cutting the mains current suddenly....so a short would not be an "inductive current"...so the most of the current would be at mains peak....
ie, if there is a short on the mains, then thats not an "Induictive current".

..its the current flowing into the short , that also flows in the mains stray L, that when it gets cut by the fuse blowing, it causes the mains transient....but this current into the short will be near zero at the mains zero cross...so if the fuse blew then, then it would mean very small mains transient spike.

 

[Aussie Susan]

What is the actual problem that you are worried about that makes you think mains transients are of concern(X-Y Problem)?
Susan

 

[barry]

Welcome to the wacky, wacky world of treez posts.

 

[treez]

What is the actual problem that you are worried about that makes you think mains transients are of concern(X-Y Problem)?

We have an otherwise good, new mains transient protector circuit...but it doesnt offer protection around 1ms around the zero cross points, so we are wondering how much of a disadvantage this really is.

 

[wwfeldman]

how do you know it doens't work "around 1ms around the zero cross points"?

what are the specs of your "new mains transient protector circuit" ?

 

[treez]

The supply capacitor of it has no replenishment at the zero cross...as the voltage is too low...it uses a shunt/clamp arrangement and we want to limit the amount of shunting, so we cannot make the cap bigger