Electronics > Power/Renewable Energy/EV's

need help to compute Irms of this topology

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f4eru:
I don't think this few ms is true. Probably moer in the 500ms-1s range.

Any load with a motor draws large amounts of power when starting.

Those cutoff curves are normalized and mandatory.
see an example : https://www.domomat.com/401003-disjoncteur-de-branchement-erdf-fiche-technique-legrand-domomat.pdf

One simple way to do load shedding on the resistive heater is to divide it down:
take a 3 phase heater resistor, and use binary division by combining:
1xR
2xR //
-> 2 bits, 4 combinations

If you use 2 of those 3-phase resistor sets in your tank :
2xR series
1xR
2xR //
-> 3 bits, 8 combinations. PF always good, no need for PWM, EMC is good also.
you can go farther down low power by serializing even more with switches.

iso14000:
HI all

I should have wrote "hundreds of ms"... of course , sorry.

dimming such a load with a triac will make abrupt conduction , leading with EMC issue, and power factor degradation. it is simply forbidden .
I can't either change the water heater resistance.

but finally , I simply described the context for the topology I purposed, let's imagine it is a exam °-D

my real challenge is math. because I found this topology almost "by accident" and after simulation it reveals a good power factor.
who can give me a clue of how to derive Irms seen by the resistance? I'm stuck

f4eru:
Nope, triac regulations are not forbidden.
There are extensive exemptions in EMC rules for allowing them.

iso14000:
mmm.... in full wave yes ... and for low power lighting yes...
and did you solve the little math?

Faringdon:
In your schem, you have the inductor in line with the resistor...so the zigzag switching  current goes through the resistive heater , which is probably a big coil structure...with lots of wiring to it........and will cause a radiated EMC problem....this is why you should have a capacitor in parallel with the resistor, and then go from there....but you need the bridge topology that i spoke of before......basically, you end up with a class D amplifier type topology......but instead of a speaker coil..you have your heater....give me a shout if you want me to send you the ltspice sims?

With a bridge topology you have power strokes all the time...whereas with your topolgy, you have an on stroke for power...and then you freewheel the current, and no current comes in from the mains during the freewheel...so you are limited in power...whereas with the bridge you get a power stroke all the time.