What is the differnce between a transformer having ferrite core and another transformer without any core (air core transformer).How these two affects the output power and leakage flux??
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\$\begingroup\$ Why the downvotes? Sounds like a reasonable question to me. \$\endgroup\$– Olin LathropJun 18, 2013 at 12:40
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\$\begingroup\$ I agree @OlinLathrop \$\endgroup\$– Andy akaJun 18, 2013 at 12:40
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5\$\begingroup\$ Question doesn't show any research effort. \$\endgroup\$– Leon HellerJun 18, 2013 at 14:42
2 Answers
The main reasons ferrite cores are used are: -
- They contain the magnetic field better than air preventing coupling to other circuits
- Higher value inductances can be made with much less copper - trading off copper loss with core loss gives the designer more options.
- Coupling of two or more windings is more effective (should this be required)
- Ferrite solutions (when applicable) are usually physically smaller than air.
The main reasons ferrite cores are not used are: -
- Permeability drifts with temperature hence air cored inductors are more stable in some applications
- Air cores don't saturate and produce 3rd order harmonics like ferrite. Useful, unless you are designing a saturable reactor of course.
- For tuned circuits in the VHF and above, ferrites are too lossy in some applications.
These are the main pros and cons.
Consider the two scenarios.
Without a core, the magnetic field strength is determined by #loops and the current (And many other factors - shape, design, resistance, but we're assuming they're identical for both transformers)
With a ferromagnetic core (Like e.g. Ferrite), applying a magnetic field will induce magnetism in the core, which will increase the magnetic field strength, which will induce magnetism in the core, which will...
As such, you can get a higher field strength from the same current with a ferromagnetic core.
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1\$\begingroup\$ Magnetic field strength is not increased with a ferrite core - the core will reduce current due to its increase in permeability. Flux density will increase of course. \$\endgroup\$– Andy akaJun 18, 2013 at 12:39
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\$\begingroup\$ @Andyaka Yes,But there is a little bit confusion about leakage flux.I think that in air core transformer its not easy to control the leakage flux.So is there any way to control the leakage flux? \$\endgroup\$– AtomJun 18, 2013 at 12:49
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\$\begingroup\$ @SHASWAT - see my answer - controlling leakage flux is much harder in air cores unless the frequency is high and conductive screens can be used. \$\endgroup\$– Andy akaJun 18, 2013 at 12:53
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\$\begingroup\$ @Andy aka: I am assuming fixed current. \$\endgroup\$ Jun 18, 2013 at 13:00