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Rick ,Jim? too

From “after ?I get this”, ???my st…uff in green

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But with a "zero volt" solid state switch HOW does the current rise instantaneously when the voltage does not? (and of course, because of back-emf, it cannot ever rise "instananeously") ya? "instananeously")??? ???[not THAT fast, maybe quickly?]?????

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If a mechanical or electromechanical switch were to be switched on every time (during power-up)? at "zero" in the AC sine wave, the voltage would start at "zero" and rise at the rate in the actual sine wave to it's peak. And depending on the inductance etc.....the current would follow. Ya,? but not so simple see below. ?

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There is no current until the thing is turned on. Ya, that must be faraday’s unspoken zeroth law!

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If the switch were to be "thrown" AT the actual peak. ......Voltage applied at the peak,? the resulting? current rise [ rate of rise? ] would be greater... significantly? greater than if it was allowed to rise at the 'normal" sine-wave rate. Ya,? and/but soon it[the rate of rise]? would decline to nothing [at 90 degrees] leaving the flux at max normal and then reverse the current and start lowering the flux, thereby ...---- too tough to write! See below ?

So what am I missing here???

Rick,Maybe this helps you, even if it is hard to understand:

pdf? 4 ---

The worse inrush happens when the AC waveform is crossing zero. At this moment, the

voltage levels are extremely low, requiring a lot of current to energize the core. Here is a picture of

what inrush looks like over time:

^this must be a sizable transformer with a high X/R so the high currents are slow to decrease, at 1kva my guess is the inrush is really the first cycle, and by the 3^rd it looks normal note the “DC offset”?????????

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d. Switching at maximum voltage crossing- no residual magnetism

This scenario will have transformer switched on during maximum voltage with no residual magnetism.

Figure 6: Waveform for case ‘d’

This case is an ideal situation as there will not be any inrush current theoretically. Remember that flux ‘B’ in the core is always 90⁰ out of phase with system voltage. Since the switching occurs at peak voltage, flux can easily start from zero and attain its nominal value. There will not be any inrush current in this scenario.

See other stuff too

A note special for Halden relating to residual magnetism /Remanence [this is the right spelling I think]??

see

f. Switching at maximum voltage crossing- maximum residual magnetism in same polarity ??and similar cases

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