air-core transformer

[EAJEL]

For air-core transformer, currently what is the maximum efficiency can be achieve ?
Is it possible to change the input voltage supply to step input of 12 V ?
Any website have the information for air-core transformer ?

Thanks for your help !!!

 

[Boncuk]

To transform voltage an air core transformer is about the lousiest device to use.

 

[Hero999]

To transform voltage an air core transformer is about the lousiest device to use.

That depends on the frequency, if it's 100MHz then an air core transformer is perfect.

 

[rezer]

That depends on the frequency, if it's 100MHz then an air core transformer is perfect.

Yes, good point. That's what I was going to say. The frequency has a lot to do with it. Iron core transformer are no good in the RF band because of all the losses.

However Eajel, if your using it for power, as I suspect you are due to your 12V requirement, than I would definitely steer clear of using one. There is too much loss by way of flux leakage. Get yourself an iron-core transformer.

 

[Hero999]

They're also good for superconducting transformers as air core transformer become nearly lossless.

 

[EAJEL]

Well, thanks for your precious oppinion.
i really appreaciate it ! ^_^

Actually, the frequency i am using is more than 100 kHz. Is there any winding techinique i should apply ? Currently, i am using multi layer solenoid winding. The efficiency is up to 20% only.

And then for some reason, i have to use wireless power transfer. That's why i chose air core transformer.

There is still a big problem. Because of i am using 12 V dc step input ( not AC power ), the back emf of primary inductor is causing great heat problem to the device. Is there any solusion i can refer to ?

Best regards for all !

 

[rezer]

Well, thanks for your precious oppinion.
i really appreaciate it ! ^_^

Actually, the frequency i am using is more than 100 kHz. Is there any winding techinique i should apply ? Currently, i am using multi layer solenoid winding. The efficiency is up to 20% only.

And then for some reason, i have to use wireless power transfer. That's why i chose air core transformer.

There is still a big problem. Because of i am using 12 V dc step input ( not AC power ), the back emf of primary inductor is causing great heat problem to the device. Is there any solusion i can refer to ?

Best regards for all !

Can you post a circuit?

 

[EAJEL]

Can you post a circuit?

actually i can't, bcoz currently i am on industrial tranning. That is the project i have to do.
you see, it's confidential... sorry...
but i hope to have as many info as possible to get this project done.
so, i need your help !

 

[EAJEL]

i have try to search the 2 website you gave me. but it's a little messy without a guildline. can you tell me more specific where can i get the info ?
thanks for your help...

 

[Boncuk]

That depends on the frequency, if it's 100MHz then an air core transformer is perfect.

Good joke, hero999

he talked about 12V. I guess he meant supply voltage.

Hans

 

[Hero999]

Actually, the frequency i am using is more than 100 kHz. Is there any winding techinique i should apply ? Currently, i am using multi layer solenoid winding. The efficiency is up to 20% only.

20% is pretty poor for a transformer, you must be doing something wrong. It sounds like the inductance is too low which is causing the magnetising current to be too high so you are loosing lots of power in resistance of the winding.

I would suggest switching to a ferrite core transformer.