Power required to reverse an electropermanent magnet

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Discussion Overview

The discussion centers on calculating the power level and pulse width required to reverse the polarity of a rod or bar shaped alnico magnet, with a focus on efficiency and the choice between AC and DC power. Participants explore theoretical and practical aspects related to the operation of electropermanent magnets.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks to determine the power level and pulse width for reversing the polarity of an alnico magnet, emphasizing the need for efficiency.
  • Another participant questions the original poster's understanding of AC versus DC power in relation to electromagnets, suggesting a lack of foundational knowledge.
  • A participant references a Wikipedia article about alnico manufacturing, implying potential issues with the proposed method.
  • One participant suggests that heating the magnet to 900 degrees Celsius, along with generating a magnetic field, may not be efficient and questions the necessity of the approach.
  • The original poster clarifies the requirement for short pulses (1ms or shorter) to reverse the magnet's polarity without heating, indicating a need for specific power and pulse width data.
  • A participant mentions the –H demagnetizing force and suggests that existing resources may not adequately address pulsating magnetic fields.
  • A link to a paper is provided, which may contain relevant equations for calculating pulse energies and widths, though it is noted to be complex.
  • Another participant expresses skepticism about the original poster's knowledge but acknowledges that they seem to have some understanding.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach or the specifics of the calculations needed. There are multiple competing views regarding the use of AC versus DC power and the efficiency of the proposed method.

Contextual Notes

Some discussions involve assumptions about the understanding of electromagnet principles and the efficiency of heating versus pulsing methods. The complexity of the calculations and the specific requirements for the magnet's physical size are also noted as limitations.

Undacuva
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Hi,
I need to know how to calculate the power level and pulse width required to revers the polarity of a rod or bar shaped alnico magnet, depending on the width. I also don't know whether to use AC or DC power.

I'm prototyping an invention and it needs to be as power efficient as possible.
 
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If you don't understand if you need to use AC or DC power, then I have to question if you know enough to be making prototypes and inventing things involving magnets and electromagnets. Do you know how an electromagnet works? What would happen if you pump DC through an electromagnet? How about AC?
Unless you are asking something else related to the AC or DC part. I assume you are asking about pumping it through the coils.
 
power enough to heat the metal to 900 degree C plus the power to produce a magnetic field strong enough to magnetise the metal while it cools. Does not sound efficient. why not just turn it around ?
 
Hi Folks,
Just to avoid confusion, I need to send pulses something like 1ms duration (or shorter), maybe 2 or 3 times a second down a wire coil around an alnico magnet to reverse its polarity. This process doesn't require heating the magnet at all. Just a strong burst of electricity.

The theoretical materials I've found out there are a bit short on the details as to the power and pulse width required for the given physical size. This design is used in switchable magnets from a lot of manufacturers.

If Drakkith knows the answer but doesn't want to give it, then he doesn't have to. ... :-)
 
Undacuva said:
Hi,
I need to know how to calculate the power level and pulse width required to revers the polarity of a rod or bar shaped alnico magnet, depending on the width. I also don't know whether to use AC or DC power.

I'm prototyping an invention and it needs to be as power efficient as possible.

http://www.google.co.uk/search?q=hy...HVCaGS0QWStIHgDA&ved=0CCMQsAQ&biw=942&bih=445

Hi Undacuva,
Are you asking about the –H demagnetising force? In that case the above websites provide a wealth of information on alnico magnets. Mind you I’ve not gone through all of them but mostly they are dealing with a constant reverse magnetic force field and not a pulsating one. Maybe there are some which will tell you the minimum required time needed.
 
Undacuva said:
If Drakkith knows the answer but doesn't want to give it, then he doesn't have to. ... :-)

Can't say I do. I just usually play intercept to a lot of the "new guys" here that ask questions that sometimes make no sense or that makes them appear like they don't know what they are doing. It seems like you know a bit more than that however. My apologies.
 

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