# Looking for some help locating a source for wire



## BigGoomba (Nov 25, 2009)

I have been trying to find a source for rectangular litz wire and keep running up against dead ends. There are a couple of companies that produce it but I cant find any seller that will sell in quantities that I can afford. I would like to spend less than $100 US. Since I am just doing experiments with building a simple DC motor , I would really like to keep it under $50.

Does anyone have any suggestions?


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## Tesseract (Sep 27, 2008)

Weeelll... there's a surplus store not too far from me that often has it (Skycraft Electronics in Orlando, FL) but other than that I usually get it from whomever is selling it on ebay or from Surplus Sales of Nebraska:

http://www.surplussales.com/wire-cable/LitzWire.html


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## BigGoomba (Nov 25, 2009)

Thanks Tesseract. I did check with Surplus Sales and they didnt have the retangular litz wire. I have found a couple of references calling it Type 8 litz wire which is what I am trying to find. There is also type 7 which I think would work for me as well.


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## Tesseract (Sep 27, 2008)

Sorry... I didn't even notice you were looking for the rectangular stuff. Yeah, MWS and New England Wire both make it, but you'll have to buy at least a roll and, well, Litz ain't cheap brand new.

Are you SURE you need Litz, though? Litz is most useful when you are dealing with high frequency CURRENTS, not voltages, and the currents in DC motors are, well, DC (even when controlled by high frequency PWM) while the frequency of the current in an AC induction motor is so low as to not even be worth mentioning w/r/t skin effect.

Anyway, set up a search on ebay for rectangular litz and sooner or later something will pop up.


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## BigGoomba (Nov 25, 2009)

From what I have been able to determine, some have been using Litz wire to reduce eddy current losses. I am trying to build my coils without an iron core. I have been experimenting with Halbach arrays. It has grown from a simple interest to a full blown obscession. A rectangular litz cable is supposed to maximize the amount of copper and I think it would be easier for me to work with in my primative workshop.

Its amazing what reasearching a maglev Barbie rollercoaster for your daughter can lead to


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## Tesseract (Sep 27, 2008)

You may find this link helpful in determining if there is any real advantage to using Litz in your application:

http://info.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html

You gotta do the reading and plug in the numbers yourself.

In general, though, Litz is rarely worth the expense and as many a switching power supply designer has learned, there is often no practical difference in efficiency, but plenty in cost, when it is used instead of plain old magnet wire. This is because a given cross-sectional area of Litz wire may be 40-60% insulation, so even though it's AC losses are much lower than a solid wire of the same area, it's DC losses are much higher.

Anyway, the key factor in deciding to go with Litz is whether the reduction in AC losses (reactive) outweighs the increase in DC losses (ohmic) and whether said improvement, if any, is worth the cost. For a Halbach array either as used in a MagLev train or brushless motor I would expect AC losses to be a vanishingly small portion... but I haven't really looked into. Interesting application, though. I love it when I get reminded of one of physics little oddities.


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## BigGoomba (Nov 25, 2009)

Thanks for the link! After reading through it and dinking around with some of the equations it really does appear that Litz would not provide any great benefit for me other than drive up my costs and give me fits trying to locate something that I dont need.

The kind of motor that I am considering will run at lower rpm (less than 500). 

Thanks for your help. Its always good to find people to bounce ideas off. There is so much information on the internet, and a fair amount of it may not be reliable, that getting pointers to sites like you posted is valuable.

-Steve


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