Power Generated by a Toroidal Current Transformer

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Discussion Overview

The discussion centers on the selection of core materials for a toroidal current transformer intended to generate power from a 7kV power line. Participants explore the implications of different materials on inductance, power output, and heat generation, particularly in the context of AC mains power frequencies.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests that Silicon-Steel may provide the greatest flux density saturation for the transformer core, while also noting that some ferrite cores might yield higher power output levels.
  • Another participant questions the suitability of ferrite for a 50/60Hz power line, stating that ferrites are typically used for high-frequency applications due to eddy current losses associated with thicker steel layers.
  • A different participant mentions that a 3% Si-Fe composition and a 50% Co-Fe composition are both good options for core material, raising concerns about potential excessive heat when stepping down from 7kV to 10V with a high primary current.
  • One participant highlights that total heat generation will include resistive wire losses and eddy current losses in the laminated core, although they express uncertainty about the specifics of the heat implications.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate core materials for the transformer, with some advocating for Silicon-Steel and others suggesting that ferrite may not be suitable for the specified frequency. The discussion remains unresolved regarding the optimal material choice and the implications of heat generation.

Contextual Notes

Participants do not fully agree on the characteristics of the materials discussed, and there are unresolved questions about the heat generated during operation and the specific requirements for the transformer design.

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I'm building various current transformers for a project at work and having trouble finding out what the best core material is to generate the most power from a 7kV power line using inductance. I have seen that Silicon-Steel provides the greatest flux density saturation but have heard that some ferrite cores can generate much higher power output levels. Now comes the greatest problem, the core total weight must be less than .5 pounds.

Can someone point me in the right direction?
 
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Do you mean like from a 50/60Hz power line? I don't think you would use ferrite for that -- ferrites are typically used for high frequency transformers, because it is not practical to use steel layers that would be thin enough to prevent significant eddy current losses.

Probably whatever is used in typical AC mains power transformers would be the best. What materials are used in power company transformers? (I don't know offhand, but could probably find it with a wikipedia.org or google search)
 
berkeman said:
Do you mean like from a 50/60Hz power line?

Right, looking around at some manufacturers, I found that a 3% composition Si-Fe is quite good for that but also so is a 50% Co-Fe composition. Would there be any excessive heat to worry about when selecting a core material or casing material coming from a 7kV line, if I were to step it down to about 10.0 V, I know the ~60A primary current will be significantly higher in the secondary but will it be too much heat for the transformer to operate effectively?
 
I'm probably not going to be of much help on this one. But the total heat will be the sum of the resistive wire losses (7kV down to 10V?) and the eddy current losses in the laminated core.
 

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