circuitos magnéticos
DESCRIPTION
circuitos magneticosTRANSCRIPT
Materiales ferromagnéticos y no magnéticos
• Ferromagnéticos – hierro, cobalto, wolframio, níquel, acero y
aleaciones entre estos metales • alta permeabilidad y fácil imantación
• No magnéticos (cobre, aluminio, madera, vidrio) – Paramagnéticos
• permeabilidad relativa es ligeramente superior a 1.0 – Diamagnéticos
• permeabilidad relativa es ligeramente menor a 1.0 Para casos prácticosla permeabilidad relativa para ambos es 1
Permeabilidad del material
• El término permeabilidad es similar al de conductividad de un circuito eléctrico
• La permeabilidad de un material está dada en función de su permeabilidad relativa, como se expresa a continuación
es permeabilidad del aire
Ley de Faraday e inducción magnética • Si se mueve un conductor a
una cierta velocidad 𝑣 a través de un campo magnético de densidad 𝐵, se induce una fuerza electromotriz (fem.) en el conductor cuyo valor está dado por la ley de Faraday con la ecuación 𝜖 = 𝐵𝑣𝐵 en donde 𝐵 es la longitud del conductor
• Si en un conductor fijo colocado en el interior de un campo magnético se hace circular una corriente, el conductor experimenta una fuerza inducida sobre él cuya ecuación es 𝐹 = 𝑖𝐵𝐵 en donde 𝑖 es la corriente que circula en el conductor
• first, the flux density increases very slowly up to point A • then, increases very rapidly up to point B • At point C, the magnetic core material has saturated
• La resistencia de un circuito eléctrico depende de la longitud 𝐵, la conductividad 𝜌 y el área A
• mientras que la reluctancia depende de la longitud 𝐵, la permeabilidad 𝜇 y el área A
• para resolver o reducir las reluctancias se aplica la misma regla empleada en resistencias conectadas en serie o en paralelo
Direcciones del flujo magnético Regla de la mano derecha
Si el dedo pulgar señala el sentido de la corriente y los demás dedos rodean el conductor, éstos indicarán el sentido del flujo magnético
Inductance
• The property of a coil of inducing emf due to the changing flux linked with it is known as inductance of the coil. Due to this property all electrical coil can be referred as inductor
Self inductance
• Whenever current flows through a circuit or coil, flux is produced surround it and this flux also links with the coil itself. Self induced emf in a coil is produced due to its own changing flux and changing flux is caused by changing current in the coil. So, it can be concluded that self-induced emf is ultimately due to changing current in the coil itself. And self inductance is the property of a coil or solenoid, which causes a self-induced emf to be produced, when the current through it changes.
The produced flux due to a current, in a circuit, always proportional to that current
K is the proportional constant, then:
and
V=
-V
L is defined as the self inductance of the coil
Unit of Inductance
• From eqn. • If V= 1V, and di/dt=1 A/s then L=1 H • Henry is the unit of inductance
-V
Mutual Inductance
Mutual inductance may be defined as the ability of one circuit to produce an emf in a nearby circuit by induction when current in the first circuit changes.
• Why would you need a gapped core? – In high power transformers, however, saturation
must be avoided at all costs because the ensuing drop in inductance leads to a sharp increase in magnetizing current, further core overload and a 'runaway' situation that often ends with smoke and flames
• What is a gapped core? – in a gapped core a small section of the flux path is
replaced by a non-magnetic medium - such as air. The term 'air gapped core' is still used even if the gap is filled not by air but by nylon or some other material immune to saturation
• Gap energy