Polarity switching electromagnet

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Discussion Overview

The discussion centers on the design and construction of an electromagnet capable of rapidly switching polarity. Participants explore the materials and considerations necessary for efficient operation, particularly focusing on core materials and the challenges associated with driving inductive devices.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that using laminated iron for the core can help avoid heat losses in the electromagnet.
  • Another participant recommends sourcing laminated cores from surplus or burned-out power transformers, noting that AC electric motors also utilize laminated cores.
  • There is a question raised about the challenges of driving an inductive device with a switched signal that has a fast rise time, indicating potential issues with eddy currents and heat losses.
  • A further elaboration discusses the reluctance of current to change rapidly in an inductive circuit, referencing the inductor equation v=L.di/dt to illustrate the relationship between voltage and the rate of change of current.

Areas of Agreement / Disagreement

Participants express varying views on the challenges of driving inductive devices and the implications of using laminated cores, with no consensus reached on the best approach or solutions to the issues raised.

Contextual Notes

Participants mention specific technical challenges such as eddy currents and the behavior of inductance in circuits, but do not resolve these issues or provide a comprehensive analysis of all relevant factors.

dorker
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I want to make an electromagnet to rapidly switch polarity back and forth. I hear the core should be made of laminated iron to avoid heat losses; is this correct? Where could I get one such core from, and is there anything else I should consider?
 
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Well since power transformers are laminated and do switch polarity efficiently, I would suggest you look around for surplus, burned out or otherwise unwanted power transformers and take your parts from that. (you can use the copper wire if you can get it out in usable lengths.) AC electric motors have laminated cores also.

You are familiar with the problems involved in driving an inductive device with a switched signal with a fast rise time?

DC
 
Last edited:
DarioC said:
You are familiar with the problems involved in driving an inductive device with a switched signal with a fast rise time?

Eddy currents and heat losses? Is there anything else?
 
dorker said:
Eddy currents and heat losses? Is there anything else?
In a circuit with inductance, current exhibits a reluctance to undergo any rapid changes. The more rapidly you try to make it change, the more stubborn it becomes.

The inductor equation, v=L.di/dt shows that if you want a high value of di/dt, you have to apply a high v.
 

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