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Generator Working and Expression :   Operation of Machine as a Generator (Conversion of Mechanical Energy into  Electric Energy) A coil is placed in a constant stationary magnetic field. Let it be rotated in the clockwise direction at an  angular velocity of Z radians per second by some outside driving mechanical torque T m . The coil  sides cut the magnetic field (or the flux linking with coil changes) and emf ( e ) is induced in the coil.  The direction of induced emf can be determined by applying Fleming’s right-hand rule or Lenz’s  Law and is marked in Fig. 1 (a ) . The coil is connected to an external load resistor R , therefore  current ( i ) flows through the coil and external load resistor. The direction of flow of current in the  coil is marked in Fig. 1 ( a ) and ( b ). When current flows through the coil conductors, they produce  their own magnetic field. The direction of this rotor field is marked by arrowhead F r . The rotor fie...

EMF Induced in a Rotating Coil Placed in a Magnetic Field :  👉 Consider a coil AB placed on the outer periphery of a soft iron solid cylindrical rotor. The stator poles  carry the exciting coils. When current flows through exciting coils flux is set up as shown in Fig. 1.  The rotor is rotating in the clockwise direction at a constant angular velocity of Z radians/sec. The  direction of the linear velocity (perpendicular to the plane of the coil) acting on conductor A is shown in Fig. 1 which makes an angle T with the direction of the field. The component of velocity perpendicular to  the field is v p  = v sin T .                                                                      FIG: 1 The emf induced in conductor A , e = Blv sin T Where, B = f...

EDDY CURRENT LOSS When a magnetic material is subjected to a changing (or alternating) magnetic field, an emf is induced  in the magnetic material itself according to Faraday’s laws of electromagnetic induction.  Since the magnetic material is also a conducting material, these EMFs. circulate currents within the body  of the magnetic material. These circulating currents are known as eddy currents . As these  currents are not used for doing any useful work, therefore, these currents produce a loss ( i 2 R loss)  in the magnetic material called eddy current loss .   The hysteresis and eddy current losses in a magnetic material  are called iron losses or core losses or magnetic losses .  A magnetic core subjected to a changing flux is shown in Fig. 1. For simplicity, a sectional  view of the core is shown. When changing flux links with the core itself, an emf is induced in the  core which sets up circulating (eddy) currents ( i ) in...

Statically Induced EMF : When the coil and magnetic field system both are stationary but the magnetic field linking with the coil changes (by changing the current producing the field), the emf thus induced in the coil is called statically induced emf. The statically induced emf may be: ( i ) Self-induced emf ( ii ) Mutually induced emf ( i ) Self-induced emf: The emf induced in a coil due to the change of flux produced by it linking with its own turns is called self-induced emf as shown in Fig. The direction of this induced emf is such that it opposes the cause which produces it (Lenz’s law) i.e., change of current in the coil. Since the rate of change of flux linking with the coil depends upon the rate of change of current in the coil. Therefore, the magnitude of self-induced emf is directly proportional to the rate of change of current in the coil. Therefore, the magnitude of self-induced emf is directly proportional to the rate of change of current in the coil, i.e., where L is a ...

Faradays Law of  Electromagnetic Induction : Faraday's laws state that an emf is induced in a circuit which is (i) Directly proportional to the time rate of change of flux enclosed by the circuit. (ii) Directly proportional to N the no. of turns of the circuit. Combining, the two laws, Faraday's laws of induction can be expressed mathematically as Here negative sign is due to Emil Lenz, who after Faraday's experiments suggested that the direction of the induced current is always such as to oppose the action that produced it. As we know Faraday's law as given by equation (ii.1) is one of the two basic relationships upon which the whole theory of electromagnetic and electromechanical energy conversion devices are based and today we have the generator and motor (electric) operating based on this theory. Also, Faraday was the first to identify emf of self-induction, i.e., here we have only one coil and it is connected to a de source through a switch. When current is flowin...

Just using Fair for this image    Similarities Between Magnetic Circuit and Electric Circuit: Magnetic Circuit  Electric Circuit The closed path for magnetic flux is called a magnetic circuit. The closed path for electric current is called an electric circuit. Flux, f = m.m.f./reluctance Current, I = e.m.f. / resistance m.m.f. (ampere-turns) e.m.f. (volts) Reluctance, S = l / 0 r a µ µ Resistance, R = ρ* l/ a Flux density, B = φ /a Wb m 2 Current density, J = I/a A m2 m.m.f. drop = φ S  Voltage drop = I R Magnetic intensity, H = NI / L   Electric intensity, E = V / d Permeance Conductance Permeability Conductivity Dissimilarities between Magnetic Circuit and Electric circuits: Magnetic circuit Electric circuit Truly speaking, magnetic flux does not flow The electric current actually flows in an electric circuit. There is no magnetic insulator. For example, flux can be set up even in the air (the best known magnetic insulator) with reasonable m.m.f There a...