Magnetic core

A magnetic core is a piece of magnetic material with a high permeability used to confine and guide magnetic fields
in electrical,electromechanical and magnetic devices such as electromagnets, transformers, electric motors,
inductors and magnetic assemblies. It is made of ferromagnetic metal such as iron, or ferrimagnetic compounds
such as ferrites. The high permeability, relative to the surrounding air, causes the magnetic field lines to be
concentrated in the core material. The magnetic field is often created by a coil of wire around the core that
carries a current. The presence of the core can increase the magnetic field of a coil by a factor of several thousand
over what it would be without the core.

The use of a magnetic core can enormously concentrate the strength and increase the effect of magnetic fields produced
by electric currents and permanent magnets. The properties of a device will depend crucially on the following factors:

• the geometry of the magnetic core.
• the amount of air gap in the magnetic circuit.
• the properties of the core material (especially permeability and hysteresis).
• the operating temperature of the core.
• whether the core is laminated to reduce eddy currents.               

Air core

A coil not containing a magnetic core is called an air core coil. This includes coils wound on a plastic or ceramic 

form in addition to those made of stiff wire that are self-supporting and have air inside them. Air core coils generally 

have a much lower inductance than similarly sized ferromagnetic core coils, but are used in radio frequency circuits

 to prevent energy losses called core losses that occur in magnetic cores. The absence of normal core losses permits

 a higher Q factor, so air core coils are used in high frequency resonant circuits, such as up to a few megahertz. 

However, losses such as proximity effect and dielectric losses are still present.

• 
  
  

  Pot core

  Usually ferrite or similar. This is used for inductors and transformers. The shape of a pot core is round with an 
  internal hollow that almost completely encloses the coil. Usually a pot core is made in two halves which fit together 
  around a coil former (bobbin). This design of core has a shielding effect, preventing radiation and reducing electromagnetic interference.
  
  
  *From Wikipedia, the free encyclopedia

Problems

Transformer Core Losses

The abi l i ty  of   i ron  or s teel   to carry  m agnet i c  f l ux   i s   m uch greater  than  i t   i s   i n  ai r,  and  thi s  abi l i ty   to al l ow m agnet i c  f l ux   to  f l ow  i s

cal l ed  permeabi l ity .   M os t   trans form er  cores   are  cons tructed  from   l ow  carbon  s teel s   whi ch  can  hav e  perm eabi l i t i es   i n  the

order  of   1500  com pared  wi th  j us t   1.0  for  ai r.   Thi s   m eans   that   a  s teel   l am i nated  core  can  carry   a  m agnet i c  f l ux   1500  t im es

bet ter  than  that   of   ai r.   Howev er,   when  a  m agnet i c  f l ux   f l ows   i n  a  trans form ers   s teel   core,   two  ty pes   of   l os s es   occur  i n  the

s teel .  One  term ed "eddy  current   l os s es " and  the other  term ed "hy s teres i s   l os s es ".

Hys te re s i s   Los s e s

Trans form er Hy s teres i s  Los s es   are caus ed becaus e of   the  fri ct i on of   the m ol ecul es   agai ns t   the  f l ow of   the  m agnet i c  l i nes  of

force  requi red  to  m agnet i s e  the  core,  whi ch  are cons tant l y   changi ng  i n  v al ue  and di rect i on  f i rs t   i n  one di rect i on  and  then  the

other  due  to  the  i nf l uence  of   the  s i nus oi dal   s uppl y   v ol tage.   Thi s   m ol ecul ar  fri ct i on  caus es   heat   to  be  dev el oped  whi ch

repres ents   an  energy   l os s   to  the  trans form er.   Ex ces s i v e  heat   l os s   can  ov ert im e  s horten  the  l i fe  of   the  i ns ul at i ng  m ateri al s

us ed  i n  the m anufacture of   the wi ndi ngs  and s tructures .  Therefore,  cool i ng of  a  trans form er  i s   im portant .

A l s o,   trans form ers  are des i gned  to operate at  a part i cul ar s uppl y   frequency .  Loweri ng  the  frequency  of   the s uppl y  wi l l  res ul t   i n

i ncreas ed hy s teres i s  and  hi gher  tem perature  i n  the  i ron  core.  So reduci ng  the s uppl y   frequency   from  60 Hertz   to  50 Hertz  wi l l

rai s e  the am ount  of  hy s teres i s  pres ent ,  decreas ed  the V A  capaci ty  of   the  trans form er.

Eddy Curre nt  Los s e s

Trans form er  Eddy   Current   Los s es   on  the  other  hand  are  caus ed  by   the  f l ow  of   ci rcul at i ng  currents   i nduced  i nto  the  s teel

caus ed  by   the  f l ow of   the  m agnet i c  f l ux   around  the core.   Thes e  ci rcul at i ng  currents   are  generated becaus e  to  the  m agnet i c

caus ed  by   the  f l ow of   the  m agnet i c  f l ux   around  the core.   Thes e  ci rcul at i ng  currents   are  generated becaus e  to  the  m agnet i c

f l ux   the  core  i s   act i ng  l i ke a  s i ngl e  l oop  of  wi re.  Si nce  the  i ron  core  i s  a  good conductor,   the eddy  currents   i nduced by   a s ol i d

i ron  core  wi l l   be  l arge.   Eddy   currents   do  not   contri bute any thi ng  towards   the  us eful nes s   of   the  trans form er  but   i ns tead  they

oppos e  the  f l ow  of   the  i nduced  current  by   act i ng  l i ke  a  negat i v e  force  generat i ng res i s t i v e  heat i ng  and power  l os s  wi thi n  the

core.

La mi na ti ng  the   I ron Core

Eddy   current   l os s es   wi thi n  a  trans form er  core  can  not   be  el im i nated  com pl etel y ,   but   they   can  be  great l y   reduced  and

control l ed by  reduci ng  the  thi cknes s  of   the s teel   core.   Ins tead of  hav i ng one bi g  s ol i d  i ron core as   the  m agnet i c core m ateri al

of   the  trans form er or coi l ,   the m agnet i c path  i s  s pl i t  up  i nto m any   thi n pres s ed s teel  s hapes  cal l ed "l am i nat i ons ".

The  l am i nat i ons   us ed  i n  a  trans form er  cons truct i on  are  v ery   thi n  s tri ps

of   i ns ul ated  m etal   j oi ned  together  to  produce a  s ol i d but   l am i nated core

as  we s aw abov e.  Thes e  l am i nat i ons  are  i ns ul ated  from  each other by  a

coat   of   v arni s h  or  paper  to  i ncreas e  the  ef fect i v e  res i s t i v i ty   of   the  core

thereby   i ncreas i ng  the  ov eral l   res i s tance  to  l im i t   the  f l ow  of   the  eddy

currents .   The  res ul t   of   al l   thi s   i ns ul at i on  i s   that   the  unwanted  i nduced

eddy   current   power-l os s   i n  the  core  i s   great l y   reduced,   and  i t   i s   for  thi s

reas on  why   the  m agnet i c  i ron  ci rcui t   of   ev ery   trans form er  and  other

el ectro-m agnet i c  m achi nes   are  al l   l am i nated.   Us i ng  l am i nat i ons   i n  a

trans fom er cons truct i on reduces  eddy  current   l os s es .

The  l os s es   of   energy ,   whi ch  appears   as   heat   due  both  to  hy s teres i s   and  to  eddy   currents   i n  the

m agnet i c  path,   i s   known  com m onl y   as   "trans form er  core  l os s es ".   Si nce  thes e  l os s es   occur  i n  al l

m agnet i c  m ateri al s   as   a  res ul t   of   al ternat i ng m agnet i c  f i el ds .   Trans form er  core  l os s es   are  al way s

pres ent   i n  a  trans form er  whenev er  the  prim ary   i s   energi z ed,   ev en  i f   no  l oad  i s   connected  to  the

s econdary   wi ndi ng.   A l s o  thes e  hy s teres i s   and  the  eddy   current   l os s es   are  s om et im es   referred  to

as  "trans form er  i ron  l os s es ",  as   the m agnet i c  f l ux  caus i ng  thes e  l os s es   i s  cons tant  at  al l   l oads .

Eddy Curre nt  Los s e s

But   there  i s   al s o  another  ty pe  of  energy   l os s   as s oci ated  wi th  trans form ers   cal l ed  "copper  l os s es ".

Trans form er  Copper  Losses  are  m ai nl y   due  to  the  el ectri cal   res i s tance  of   the  prim ary   and

s econdary   wi ndi ngs .   M os t   trans form er  coi l s   are  m ade  from   copper  wi re  whi ch  has   res i s tance  i n

Ohm s ,  ( Ω  ).  Thi s  res i s tance oppos es   the m agnet i s i ng currents   f l owi ng  through  them .

When  a  l oad  i s   connected  to  the  trans form ers   s econdary   wi ndi ng,   l arge  el ectri cal   currents   f l ow  i n

both  the  prim ary   and  the  s econdary   wi ndi ngs ,   el ectri cal   energy   and  power  (  or  the  I   R  )  l os s es

occur as   heat .  General l y  copper  l os s es   v ary  wi th  the  l oad  current ,  bei ng alm os t  z ero  at  no-l oad,  and

at   a  m ax im um   at   ful l -l oad  when  current   f l ow  i s   at   m ax im um .   Trans form ers   wi th  hi gh  v ol tage  and  current   rat i ngs   requi re

conductors  of   l arge cros s -s ect i on  to hel p m i nim i s e  thei r copper  l os s es .

Then we can def i ne an  i deal   trans form er as  hav i ng:

1.  No Hy s teres i s   l oops  or Hy s teres i s   l os s es    →  0

2.   Inf i ni te Res i s t i v i ty  of  core m ateri al  gi v i ng z ero Eddy  current   l os s es    →  0

3.  Zero wi ndi ng res i s tance gi v i ng z ero  I R copper  l os s es    →  0

In  the  nex t   tutori al   about   T ransf ormers  we  wi l l   l ook  at   Tr a n s f o r m e r   L o a d i n g   of   the  s econdary   wi ndi ng  wi th  res pect   to  an

el ectri cal   l oad and s ee  the ef fect  a "NO-l oad" and a "ON-l oad" connected  trans form er has  on  the prim ary  wi ndi ng current 

Destination

I.E.S. Paper 1

                                                     

                                           I.E.S. (Infinite Energy Source)

As the name implies the project itself is an attempt to achieve self sustainability for its operation i.e. infinite energy. I have been trying to make a SIMO (Single Input Multiple Output) system. Input given to the system is in form of electrical energy and output energy obtained is actually a proper combination of mechanical and electrical energy. Block diagram shown below would make it clear to all.

It is a project which needs deep study of the concepts of Electromagnetism (Induction, Flux lines, Faraday Law and etc.) and sort of expertise to select the appropriate material. I could successfully achieved what I wanted to.  Soon I’ll update the blog with the original images and videos of my project to let you know about it more.

Continue……….

Written By-

Navin Chand Paneru

Project Assistant 

E-mail-navinpan1@gmail.com

Paper will publish after some time.