ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
nec 110.3 (B)
by gfretwell - 09/22/21 11:11 PM
Grounding electrodes
by gfretwell - 09/07/21 03:41 PM
Looking For Electricians in the Midlands
by Alex247 - 09/06/21 05:26 AM
New in the Gallery:
Now you know.
Now you know.
by Tom_Horne, September 7
February, North East Indiana
February, North East Indiana
by timmp, July 25
Who's Online Now
1 members (HotLine1), 46 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#200589 04/09/11 09:40 AM
Joined: Feb 2011
Posts: 28
Vlado Offline OP
Member
Link
Who finds this article funny? smile

Last edited by Vlado; 04/09/11 09:41 AM.
Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
It is very n1ce to see that someone finally crunched the numbers, and put this fairy tale to rest.

Joined: Jul 2004
Posts: 9,663
Likes: 4
G
Member
I have a 250kv line behind my house and I played around with a lot of things over the years in response to urban legends I have heard, nothing was even enough to get an F40 tube to glow.


Greg Fretwell
Joined: May 2005
Posts: 984
G
Member
I had to laugh at #5. If the voltage is indeed dependent on the current flow (instead of the turns ratio) every transformer in the world would have a variable voltage output depending on how loaded it was at that moment.

It's sad to think that there are 'educated' people who belive this drivel...but I'va always said that there's a world of difference between 'educated' and 'smart'.


Ghost307
Joined: Jul 2004
Posts: 9,663
Likes: 4
G
Member
Transformers do have a variable output based on the current. Usually in a well engineered transformer the variation is minimal but in this "stealing power scheme" the transformer is far from ideal. The basic problem is this is a one turn transformer and there is no iron to transmit the power to the secondary so you will not be moving much power.
I tried a few different things over the years, just to bust myths and the short answer is none of them work.


Greg Fretwell
Joined: May 2005
Posts: 984
G
Member
I'm not talking about the 'regulation' of the output voltage which is function of loading, not input voltage.

Yep, air-core transformers are not very good for this application. That was one of the things that I found while building my high school science fair exhibit (I built a step-down transformer) I could drop the voltage output to nearly zero as I gradually withdrew the metal core. Since I ende up having to wind a total of 5 coils during design and testing...I got pretty good at counting the turns.


Ghost307
Joined: Jul 2004
Posts: 9,663
Likes: 4
G
Member
I have a pretty neat gadget for that. It is a mechanical rotation counter, used as a primitive tach.
You can chuck your core up in a drill and still keep an accurate turn count. I made up a bunch of 500 turn coils for a motor science fair project my daughter had in high schools.


Greg Fretwell
Joined: May 2005
Posts: 984
G
Member
All I had was my memory and an old fashioned drill brace fitted to a wooden frame. Every time I got to 50 I stopped and wrote it down in a notebook. I would have given you 2 weeks allowance to let me use a mechanical counter like that.
smile


Ghost307
Joined: Feb 2011
Posts: 28
Vlado Offline OP
Member
No doubt,the story about farmer stealing kilowatts of power in a desribed way is a pure bullshit.I wonder who has enough imagination to invent and spread nonsenses like that.Few comments regarding the article which has some good but weak & funny points as well. smirk

(4)

Mentioned 150 A max for 230 kV power line is a funny figure.This current is even smaller than expected average current of such power line.Single Al/Fe phase conductor cross section 120/20 mm˛ can withstand 400 A continously and 240/40 mm˛ about 650 A. For example,typical EHV line,say 500 kV one,with boundled phase conductor is designed to carry about 1000 A.Of course,in real situation ,the current will depend on loading of consumers.

(7)

Maximazing power by choosing arbitrary load (Z=200 ohms) is a no-no. The conclusion about very low power factor is correct only for low output impendances.With higher impendances power factor increases (power throughput doesn't however).

(10)

Inserting iron core in the coil in such situation will not particularly help!Actually I think it will just worsen the thing. As regards advice to farmer how to increase efficiency here are my 2 cents.He may built a resonant converter with natural frequency 60 Hz ,by connecting HV capacitor to the coil.Adequate capacitor size for 1600 H coil would be 17.6 nF.With Q factor in the range 100-200 ,and B-field given in the example ,extracted power will be couple of watts.This is still far from being enough for his needs.Not to mention economy (good point 9 in the article).Good resonant converter for such purpose will not be cheap.Finally,the author seems to be completely forgetting about fact farmer is dealing with 230 kV line and he should better think of utilizing E-fields than B-fields!Calculate specific energy in elementar space volume created by E-field and B-field of 230 kV line and see.


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
HCE727
HCE727
Delaware County, PA, USA
Posts: 187
Joined: November 2005
Top Posters(30 Days)
timmp 3
FGBY 2
Popular Topics(Views)
283,041 Are you busy
216,770 Re: Forum
203,168 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5