I need to know the number of turns that should be connected to 220 volts AC. I can measure resistance only, I don't have a device that measures inductance.
If I need the primary coil to be 220V / 1A (For example). Can I omit the inductance and turn (wound) the coil so that it has 220 ohm of resistance only? Does that make a major difference in the current?
If I can not do that, How can I know the number of turns without knowing the inductance?
Thank you very much,
Answer
You have to consider that the primary (on its own with no secondary current) is just an inductor and you don't want this to be taking 10 amps sat there doing nothing else. So what primary inductance do you need?
Try 1 henry - it has an impedance at 50 Hz of \$2\pi fL\$ = 314 ohms and will take a reactive current of 700 mA (RMS) from a 220 V AC supply. Too much?
Quite possibly so maybe aim for 10 henries and the current drops to 70 mA.
Somewhere in this region will be the optimum but you cannot know this until you have calculated how many turns produce so-many henries. To do this you need to know the \$A_L\$ of the core. It's normally specified in \$\mu H/turn^2\$ and a typical figure for silicon steel laminate might be about 10 \$\mu H/turn^2\$.
Basically 1000 turns gets you 10 henries and 316 turns gets you 1 henry.
On core saturation, with 1000 turns and 70 mA, the ampere turns (magneto motive force or MMF) is 70. With 316 turns and 700 mA, MMF is 221 and this scenario is much more likely to saturate the core but, without knowing the core dimensions nor having a BH graph it is difficult to predict.
Can I omit the inductance and turn (wound) the coil so that it has 220 ohm of resistance only?
Don't be silly - resistance isn't going to help here.
Here's a useful and general "slide" taken from the Ferroxcube soft ferrite handbook: -
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