2007-10-05 17:45:41 · 4 answers · asked by deepak_8584 1 in Science & Mathematics ➔ Engineering
Residual magnetism is one of importan properties of ferromagnetic materials.
As the Core of DC machine is made of feromagnetic material , the residual magnetism exists.
In ferromagnetic materials, the magnetic power increase with the increase of the currrent flow thru cols.
Whn current is reduced to zero , still those colis have magnetic power left in it.
u can understand more by see magnetic curves of the material.
This residual magnetism helps in the starting of motor and building up of speed.
If the field colis are given oppsite supplies then the speed doesnt gets build up.
Hence residual magnetism is used to start the machine
2007-10-07 01:55:01 · answer #1 · answered by Sun_India 2 · 3⤊ 0⤋
Residual Magnetism
2016-10-05 08:46:19 · answer #2 · answered by ? 4 · 0⤊ 0⤋
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In a generator, residual magnetism, also known as 'remanence' or remanent flux, is due to the hysteresis of the magnetic material in the core. When the current is removed, the magnetic flux often remains at some non-zero value. This is a characteristic phenomenon of ferromagnetic materials. The residual voltage after a generator has been stopped is due to the capacitance of the insulation system. On medium voltage generators, this capacitance can store a fairly significant amount of charge, and will give an unpleasant shock if you happen to contact it before being discharged. The other answerer mentioned that it is residual magnetism which is responsible for some form of excitation. In large generators, the field excitation is practically always externally controlled. In medium and smaller generators, a permanent magnet exciter is used to generate the current for field excitation. And, while permanent magnets do offer the most obvious form of residual magnetism, their magnetism is not dependent on generator currents, as implied by the earlier answerer.
2016-03-29 09:52:04 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Residual Magnetism is needed for instant voltage build up. If there is no residual magnetism, then we may connect machine with a battery for just 5-7 seconds to develop some magnetism.
2015-08-11 18:55:48 · answer #4 · answered by Mayank 1 · 0⤊ 0⤋
In Dc machine poles (core) materials are made of special magnetic material that will hold some amount of magnetic effect even after supply is cut off.It is the special property of a DC machine .If we make reverse instantaneous power supply thro battery it will lose.Again after feeding right polarity it will hold its residual magnetism.Because of this residual magnetism set up in the field poles, no need of external excitation, it will work as a self excitation Generator.
2007-10-06 01:07:39 · answer #5 · answered by ricky414 5 · 0⤊ 0⤋
when the power is switched off to an electro magnet, it will retains some magnetic power, and the retained magnetic power is called residual magnetism. Example, standby generator. Once the generator is started the residual magnetism in the field produce small amount of voltage and then the same voltage is fed to the field to increase the magnetic field which will produce more voltage than earlier rotation and so on untill the rated voltage is produced. If there is no residual magnetism in the magnetic field, the generator will not produce any voltage.
2016-03-16 06:52:14 · answer #6 · answered by Anonymous · 0⤊ 0⤋
residual magnetism is due magnetic field in coils like motors if this coil exposed to flow current or mag antic field for while then this current or the mag antic field stopped by switch off the machine it will be some residual magnetism left in the coils due to to we magnetize the coil by the current flow in the coil this residual it useful in generators to produce power, you cannot get rid of this residual unless you connect the internal machine coil to ground i.e. earthing
2007-10-05 18:09:13 · answer #7 · answered by Anonymous · 1⤊ 0⤋
it is the property of ferromagnetic material,that when some external field is applied to these material they magnetised .after removing field they still shows some magnetic existance,this is called residual magnetism
2016-04-19 03:41:39 · answer #8 · answered by ? 1 · 0⤊ 0⤋
RESIDUAL - LEFT OVER
MAGNETISM- ITS A PROPERTY EXHIBITED BY THE FIELD ...
RESISTOR,INDUCTOR,CAPACITOR ARE THE ENERGY STORING ELEMENTS. THEY STORE SOME AMOUNT OF ENERGY EVEN AFTER THE REMOVAL OF SUPPLY.
FIELD WINDING IS A FORM OF INDUCTANCE SO IT STORES SOME ENERGY IN IT AND THIS ENERGY IS USED FOR VOLTAGE BUILD UP IN IT....
2015-08-21 03:50:43 · answer #9 · answered by ? 1 · 0⤊ 0⤋