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# Re: [FEMM] alnico5 versus ceramic5 ?

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- Subject: Re: [FEMM] alnico5 versus ceramic5 ?
- From: David Meeker <dmeeker@ieee.org>
- Date: Mon, 26 Jan 2004 11:31:25 -0500
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`Bengt Dahlberg wrote:`

> `Hello Keith.
> Thanks for your answer but it leaves me a little bit pussled. The thing is table 2.1 at this webpage http://www.magnetsales.com/Design/DesignG.htm . Looking at that tells me that "alnico5" is almost twice as strong as the "ceramic8", am I reading this table the wrong way or what. Where I'm coming from (speakerbuilding) alnico is way better than ferrit so this a little bit confusing.
> Best regards. Bengt Dahlberg Sweden`

`
Energy product isn't the whole story--the resulting flux density depends on the magnet's characteristics and the circuit that you are driving. The way that people classically think about this is in terms the "load line". There's a nice explanation of load lines at:
http://www.magnetweb.com/Sect4A.htm
The load line is essentially mapping the reluctance of the device external to the magnet onto the second-quadrant demagnetization curve such that the operating point of the magnet can be obtained via graphical means.`
`An interesting exercise is to plot the demagnetization curves of Alnico 5 and Ceramic 5 on the same graph, like in the attachment. If the load is relatively low reluctance, the load line is very steep, and the alinco produces a high flux density. If the load has a relatively high reluctance, the load line is shallow, and the ceramic produces a higher flux density than the alnico. In general, you have to design your magnetic device with the type and grade of magnetic material in mind, so that the magnet is presented with a load that is compatible with the magnet's properties and dimensions.`
`Dave.`

- References:
  - [FEMM] alnico5 versus ceramic5 ?
    - From: "Bengt Dahlberg" <d.bengt@bredband.net>
  - Re: [FEMM] alnico5 versus ceramic5 ?
    - From: Keith Gregory <K.Gregory@lboro.ac.uk>
  - Re: [FEMM] alnico5 versus ceramic5 ?
    - From: "Bengt Dahlberg" <d.bengt@bredband.net>

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