#1526 Inductor Magic

Episode 1526
I show that 1 + 1 = 4

[TheRcEngineer]

The inductivity rises with the turns squared so double the turns 4 times the inductivity.

[guytech]

You missed one example on the Common Mode inductor: Short out one of the windings and measure the inductance of the other winding. The common Mode inductor can also function as a 1:1 transformer. By shorting out one of the windings you measure the leakage inductance. You could also do a demo of using the common mode inductor as a 1:1 transformer.

Another discussion is the core material: Ferrite vs, powder core vs, plate (ie Silicon Steel), vs MPP. Then also air gapped core, Saturation, eddy current, etc.

[argcargv]

Excellent puzzle! Just a side note about harvesting inductors... most inductors are highly nonlinear devices and so inductance alone is often not enough to characterize them. Most chokes use ferrite material that is intrinsically lossy as their purpose is to block ac not store energy. Similarly for common mode inductors, they are likely to saturate early as the common mode is small and the differential mode magnetic fluxes cancel... so typically the magnetization of a common mode choke is low in use. So, although the inductance is high, it usually wouldnt work well in an application like a buck conerter where energy storage is key.

[johnwest]

A really good way to demonstrate field opposition and the reason for those little dots. Well done.

[Manf-ftzk]

Maybe it is known to many visitors of your channel that the inductivity goes with n². There is something that can be achieved with that rule.
If you need to adjust an inductor you can take two cylindrical fixed inductors with open field and align them with their field coupled until the inductance fits. With two 1 mH inductors one can build inductors from 2 mH to something below 4 mH. (It is better to just couple the field in common direction.)

[blog]

Proportional to the square of the ratio of the turns ...double the turns Quadruple the inductanc

[lawrencejelsma]

When throwing out discarded electronics with them notice all RLC components used to filter the signal frequencies. Calculation of frequency impedance done from Laplace and Fourier transforms. I have many Butterworth, Chebychev RLC filter designs around a central operating frequency fc. Inductors with digital signals (since analog is now FM or AM sound) to still filter out unwanted frequency noise around a center frequency. Low pass, High Pass, Band Stop, etc make sure at a certain fc certain lower and ceetain higher frequencies are choked off. It is neat when guys hook up filter design experiments with a frequency input of fc and seeing fc-∆ and fc + ∆ on an oscilloscop at Vo to load experiments.

[fredmitchel]

We used whatever the spec called for and had like a huge GED RAD bridge...with varied test frequency and current settings...our GED rad reported DC resistance..too

It is nice newer hand heldish- instruments will measure inductance...

And clever Oscope readings..if your doing your own switching power supplies...make sure you avoid saturating your ferrite and wire wound combo...

[analog_guy]

The dark-colored cylindrical inductors you began with possibly have such low inductance because they may be gapped (having a gap in the high-permeability material so the magnetic flux must pass through an air gap at some point). A gap is used in high-current applications to raise the current required to saturate the material, or to increase the stored energy in applications such as step-up or step-down voltage converters.

[frankowalker]

The feilds exite each other in the last example as opposed to canceling each other out.

[aduedc]

L=μ(N^2)A/l
L~KN^2
N is # of turns
So you would expect doubling the number of turns (which what you are doing) square the value of inductor.

[Clark-Mills]

A dabbler digital electronics dude here... I knew it all... until the end! :)

[therealjammit]

The two inductors in series weren't sharing the same magnetic field while the two inductors on the same core did share the same magnetic field. The two magnetic fields on the same core aided each other.

[QMSSLABNPN]

Hi, when two inductors are in mutually series connection, the final inductance is:
L=L1 + L2 + M(L1 +L2)

when M is mutuall coefficient

[nvrumi]

I didn't know this, but on seeing the other comments about inductance being proportional to the square of the number of turns, it makes perfect sense. Thanks!

[glevideo]

It was a surprise to me. It was also a surprise when I looked up your LCR meter and found it was over $500. Wow! I'd like to find a nice little LCR meter but that is a little pricey for me.

[hugocoolens]

It's L1+L2+2M M is the mutual inductance i.e. k*sqrt(L1*L2), k being the coupling factor

[AnalogDude_]

Cool information, for a future "power" project for witch I'm gathering parts and needs a common (to safe space) inductor.
At the moment i don't have a mm with that function to measure Henry, i wanna make them myself and i'm looking at a roll of 1KG of 1mm emailed wire. the shop around the corner put some recovered inductors away for me. they are like 1 inch diameter. never needed them before, some E.Q. guitar pedal also uses them, bought them, but they are SMD and really small.

Would you do a video on how to make/calculate inductors (without having the right tool), how to choose the right sized torroid or requirements for them. thanks in advance.

[johndunn]

Whats needed to be said is that there is magnetic coupling. If these turns of wire were not coupled then you would be able to measure the inductance with your meter.

[reylambarte]

In such connection the two inductance add up plus twice the value of the mutual inductances of the two coils