The Solenoid/Electromagnet

[Hrothgar]

It occurs to me that the solenoid has been around for nearly 200 years. Yet I can't seem to find any evidence that anyone has made significant improvements on it in that time. It needs more attention as it eventually becomes a tool any any inventor/DIY's repertoire and I would like that attention to be shown here. Experiments, experience and ideas to help those such as myself who have had zero practical experience in electromagnetism, But who really want to learn as a good solenoid can be crucial to an experiment or project.

[Farmhand]

Hi Hrothgar, Do you mean just a solenoid type of coil or a solenoid as in a
device for actuating some mechanical apparatus ?

I think a "Solenoid" is just a close wound helical coil. And depending on the
behavior wanted from it depends on how it is made in general. A solenoid can
be used as a converter, like in a boost converter and it's only purpose is to
store energy then discharge it, as a voltage converter. Or a solenoid can be
for an actuator for a valve, or it can be for a Tesla coil, three quite different
uses and the winding types differ accordingly.

Boost converter coils are wound usually on a ferrous core and made so that
they are compatible with a certain frequency. These don't have to be
solenoids but many are.

Actuator solenoids are more of an electromagnet wound for force and current
considerations.

Tesla coils can be single layer solenoids wound to produce a high voltage at a
certain frequency.

Boost converter with synchronous rectification can be well over 90% efficient.
There isn't really much to improve on. Can you be more specific about your thoughts ?

Solenoid - Wikipedia, the free encyclopedia

In physics, the term refers specifically to a long, thin loop of wire, often wrapped around a metallic core, which produces a uniform magnetic field in a volume of space (where some experiment might be carried out) when an electric current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets.

Cheers

[chainmailleman]

It occurs to me that the solenoid has been around for nearly 200 years. Yet I can't seem to find any evidence that anyone has made significant improvements on it in that time. It needs more attention as it eventually becomes a tool any any inventor/DIY's repertoire and I would like that attention to be shown here. Experiments, experience and ideas to help those such as myself who have had zero practical experience in electromagnetism, But who really want to learn as a good solenoid can be crucial to an experiment or project.

Patent US512340 - NIKOLA TESLA - Google Patents

Nikola Tesla patent 512340

I've been advocating this particular "improvement" for some time for particularly efficient electric motors using magnetic attraction. If you take a coil with the same number of turns, and compare it to this configuration using the same power supply, you will find this coil design produces a much stronger field for the same applied power (about 75% gain).

These coils also store much larger amounts of energy in the electric field, which causes huge current spikes (amperage = change in the electric field/time) along with huge voltage spikes (voltage = change in the magnetic field/time) when the power is "Abruptly Disrupted".

......said too much

[Hrothgar]

So much for me being original

Well Chain, looking at the patent I see why it's an improvement as the coil b. acts as gears working with each other if you picture the direction of the flux spinning around the wire. figure a. being a standard coil has every flux orbit in a state of reluctance with the ones adjacent to it.

Does it run cooler?

[Hrothgar]

Hi farmhand

I am referring to the area of understanding & building electromagnets in general. How to and why.

[wrtner]

Is not the essence of a solenoid (as opposed to an electromagnet)
that there is a core which can push or pull and actuate things?

If so, how would a pancake coil be engineered to do this?

[chainmailleman]

Well Chain, looking at the patent I see why it's an improvement as the coil b. acts as gears working with each other if you picture the direction of the flux spinning around the wire. figure a. being a standard coil has every flux orbit in a state of reluctance with the ones adjacent to it.

Does it run cooler?

A coil will heat up if it produces a magnetic field (stator) in opposition to another magnetic field (rotor). When you smash two opposing fields together, alot of heat is produced, much akin to slamming two cars together head on.

Heating due to ohmic resistance will also play a factor, but the heat generated is minimal compared to a rotating induction motor.

Things will stay cool if your motor/generator is not fighting itself with Back EMF.

Back EMF is EMF generated in OPPOSITION to the APPLIED EMF.

[Hrothgar]

Is not the essence of a solenoid (as opposed to an electromagnet)
that there is a core which can push or pull and actuate things?

If so, how would a pancake coil be engineered to do this?

Actually you can do the same thing around a rod if it is only wrapped in one layer of wire. After that it gets tricky.

[Hrothgar]

Cool Runnings

So yes generally it runs cooler than it's contemporary counterpart given the same operating conditions.

[Farmhand]

All the fallacies about Tesla's COIL FOR ELECTRO-MAGNETS are put to bed in
this thread at OU.com. The patent is deciphered.

Tesla's "COIL FOR ELECTRO-MAGNETS".

There is no extra magnetization force from a serial connected bifilar coil is the
same amount of wire and turns is used as compared to a normal coil.

The experiments have been done by those who want to to prove it to ourselves..

The patent covers all coils not just pancakes. READ THE PATENT, and the
thread. It's worth it.

Please just ignore the posts by Synchro and Milehigh, they are extremists.

The truth of the matter is that some quite smart people could not decipher
the patent, I think i nailed a couple of the main points.

Cheers

P.S. Here is the claims of the patent and my understanding of it below.

Tesla's Claims in the patent are correct that is the main thing.

Quote

What I claim as my invention is

1. A coil for electric apparatus the adjacent
convolutions of which form parts of the
circuit between which there exists a potential 45
difference sufficient to secure in the coil a capacity
capable of neutralizing its self induction as hereinbefore described.

2. A coil composed of contiguous or adjacent
insulated conductors electrically connected 50
in series and having a potential difference of
such value as to give to the coil as a whole a
capacity sufficient to neutralize its self induction
as set forth. NIKOLA TESLA

Here is what I think the claims are saying. If the voltage is too low, then the distance between the capacitor "plates" is too great for the capacity to be effectively used.
ie. If the conductors have insulation 5 mm thick then using 1 volt won't utilize the capacity very well and the capacity will not then contribute to the lowering of the resonance frequency. Kinda like trying to use 1 volt with a HV parallel plate air capacitor with 10 mm spacing between the plates, it won't work very well.

It makes sense to me.

Weather or not the coil is special is not a concern to me. The patent claims are correct and I think that is what he means when he says the words in bold above.

Rather than trying to argue angles or such things why not just take the claims and find if they are correct or not. Tesla's patents do not need to be dismissed or defended if they are making claims that are true. Simple. Any claims not made by Tesla are other peoples making.

..

[Hrothgar]

I noticed it wasn't a single layer like in the patent

I noticed you used multiple layers of wire given the description. It seems to me it would be nearly impossible to keep a consistent resistance free configuration after the first layer. I don't think Tesla needs defending as Epic Rap battles of History on you-tube have done that quite nicely.

[chainmailleman]

There is no extra magnetization force from a serial connected bifilar coil is the
same amount of wire and turns is used as compared to a normal coil.

The experiments have been done by those who want to to prove it to ourselves..

..

I wish to openly challenge this statement. Unfortunately the video I was wishing to provide showing an experiment proving that the coil does create a stronger field per watt, has been made private. I do have the video saved on my hard drive, although I think if I upload it, I will be violating copywrite as it is not my material. I have replicated the experiment and have come up with the same conclusion using a 12 volt power supply, a 15 ohm 5 watt resistor, and various coils in different configurations all containing the exact same amount of copper wire.

P.S. I did read the patent many, many times. I have not "deciphered" it incorrectly. Tesla doesn't really mention magnetism even though it's part of the title. The claims of a stronger field per watt are coming from me. I don't know where you gathered that I was claiming Tesla.

[boguslaw]

Lot of questions ....Well, maybe both statement are true ? Insulation of ordinary enamelled wire is tiny and thus voltage required to use distributed capacitance is low, I think.
Does this distributed capacitance always correctly interacts with the inductance of this coil ? Why and how ? Does the magnetic field produced is bigger when DC current is applied of some pulsating DC of certain frequency ?

If that happen surely it will give more power to the created magnetic field, which is in other cases consumed into resistance heating. In such case pancake bifilar coil wound be essentially close to room temperature superconductor or self-adjusted tank circuit at resonance.

Can we isolate the reason why magnetic field from such coil is stronger ????

[wrtner]

I have never understood the pancake coil but thought
it was about Tesla's high voltage high frequency work,
and a coil which generated a good magnetic field
without the inductance that interferes with HV/HF
circuits. Is this right?

[Hrothgar]

Flippin pancakes

I have never understood the pancake coil but thought
it was about Tesla's high voltage high frequency work,
and a coil which generated a good magnetic field
without the inductance that interferes with HV/HF
circuits. Is this right?

The pancake coil itself may have been illustrated mainly for communication, the visual of the wire turning back on itself is probably easier to understand this way.