[SOLVED] Inductors in parallel

[sharikbaig]

One of my friends asked me this very interesting question,
"If i connect 3 heating coils of 250W each in parallel supplied with 100V, how much current would this arrangement draw?"
I would have very easily calculated the current for 1 heating coil by P=VI, but the twist comes in when there are 3 coils connected in parallel. What difference would that make..? Any help will be appreciated.

 

[ads-ee]

You must not have tried to answer this using a google search...The following explanations about parallel inductors showed up, which are all pretty decent.

https://www.electronics-tutorials.ws/inductor/parallel-inductors.html
https://cie-wc.edu/11-29-11.pdf
https://www.allaboutcircuits.com/textbook/direct-current/chpt-15/series-and-parallel-inductors/

This is just the first 3 links that show up.

The calculation ends up with the inductors being combined into a thevenin equivalent inductor, which gives you the current. And the amount of current through each inductor is based on the ratios of the inductances.

I suggest you read the above links and try figuring out the calculations and come back if you still have problems.

 

[D.A.(Tony)Stewart]

Maybe just semantics, but heating coils are not big on inductance from line frequency and the word heating is a clue that they are mainly resistors that are coiled.
The inductance part doesn't dissipate heat.

Another thought is that the power source is assumed to be << 1% of the net load resistance, so the voltage drops .<1%.

Thus you can add up power ratings to get 3x the current and power as voltage is constant.

 

[Audioguru]

The OP forgot to tell us if he is feeding DC into the inductors or if the inductors are used for medium frequency induction heating of a metal bar inside each coil with heating caused by eddy currents.

 

[chuckey]

Inductance or not, each heater has 100V across it, so if one dissipated 250W, each one dissipates 250 W, so an individual current is 2.5A, so total current is 7.5A and total power is 750W.
Frank

 

[sharikbaig]

Inductance or not, each heater has 100V across it, so if one dissipated 250W, each one dissipates 250 W, so an individual current is 2.5A, so total current is 7.5A and total power is 750W.
Frank

Thanks Chuckey, this makes sense. I also concluded with the same answer for DC input voltage. However for AC input, Power Factor will also have to be considered, though we dont have Power Factor rating of those coils. So this thread is solved for me :smile:

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[SOLVED]
Thanks everyone, you all helped amazingly. So happy to be a part of such community. ☺

 

[D.A.(Tony)Stewart]

If Pwr loss is fixed then PF is irrelevant, as inductive current vector component is lossless.