Solenoid core, solid or laminated?

[Njguy]

I am creating an electromagnet that switches polarity at around 200-500 hz. I was wondering if I should stick with a solid mild steel core, or try a laminated electrical steel core. I think with grain oriented electrical steel for the lamination would better. From what I understand solid cores deliver better flux, but the laminated cores reduce eddy currents. I was wondering if anyone had any knowledge on this that they would like to share. It seems that a laminated grain oriented electrical steel core would still deliver better magnetic flux than the solid mild steel core. But I wouldn't know. Thanks guys.

 

[johansen]

transformer iron loss is typically 1 to 10 watts per kilogram at 1.3-1.7T at 60 Hz. there is a frequency squared component but for a solenoid and lower flux densities you can probably estimate linear losses according to frequency. however the flux density is a major component and will have the greatest effect on iron losses.

you're pretty much stuck with laminated stock at that frequency, but if its a small solenoid then you might be able to get away with a solid core.

the biggest challenge would be cutting the sheet metal in a way you can build a solenoid from...

 

[Njguy]

Would you see any potential problems of using a solid core at 250 hz+ polarity switching?

 

[johansen]

can you post a cross sectional diagram of what you need to build?

 

[shortbus=]

You don't need to use flat iron sheet for this type of core. It can be made from a bundle of wire also, this makes a round core easier to make. No matter which you use, flat sheet or wire, the main thing is to put a coat of paint on the individual pieces. This helps to stop the eddy currents.

You also didn't say how long the magnet would be on. For short time use, less than a minute, a solid core may be OK.

 

[Njguy]

Does anyone know of an example where the core lamination's are glued together? This would be in order to aid in the making more complex core shapes.

 

[Mr RB]

I am creating an electromagnet that switches polarity at around 200-500 hz.
...

At 500Hz you are talking about something like a speaker. There's no reason you could not use an air core especially with the common availability of all these super magnets now.

 

[Njguy]

No it's a motor

 

[alec_t]

Perhaps you could mix iron filings with epoxy resin to mould complex core shapes?

 

[ronv]

can you post a cross sectional diagram of what you need to build?

Ditto..................