AC Motor Calculation
Calculate the Full Load Current of AC Motor
INDUCTION MOTORS ANALYSIS
Equivalent circuits of three-phase induction motor
Estimation of Induction Motor Parameters
Estimation of Induction Motor Parameters Program
Power and Efficiency
Power flow in an Induction motor
Losses and Efficiency of Induction Motor
Program
Calculation Equivalent of induction motors program
Showing posts with label Induction. Show all posts
Showing posts with label Induction. Show all posts
Friday, April 10, 2009
Friday, March 20, 2009
Direction Of Induced Current
Lenz’s Law
The direction of the induced current may also be found by this
law which was formulated by Lenz.1835.
Lenz Law states, in effect, that electromagnetically induced
current always flows in such a direction that the action of the
magnetic field set up by it tends to oppose the very cause, which
produces it.
This statement will be clarified with reference to Figs.1.15 and
Fig.1.16. It is found that when N-pole of the bar magnet
approaches the coil, the induced current setup by the induced EMF
flaws in the anti-clockwise direction in the coil as seen from the
magnet side. The result is that the face of the coil becomes a Npole
and so tends to retard the onward approach of the N pole' of
the magnet (tike poles repel each other). The mechanical energy
spent in overcoming this repulsive force is converted into electrical
energy, which appears in the coil.
When the magnet is withdrawn as in Fig.1.16, the induced
current flows in the clockwise direction, thus making the face of
the coil (facing the magnet) a S-pole. Therefore, the N-pole of the
magnet has to be withdrawn against the attractive force of the
S-pole of the coil. Again the mechanical energy required to
overcome this force of attraction is converted into electric energy.
It can be shown that the Lenz's law is a direct consequence of law
of conservation of energy. Imagine for a moment that when N pole
of the magnet (Fig.1.16) approaches the coil, induced current flows,
in such a direction as to make the coil face a S-pole. Then due to
inherent attraction between unlike poles, the magnet would be
automatically pulled towards the coil without the expenditure of
any mechanical energy. It means that we would be able to create
electric energy out of nothing, which is denied by the inviolable
Law of Conservation of Energy. In fact, to maintain the sanctity of
this law, it is imperative for the induced current to flow in such a
direction that the magnetic effect produced by it tends to, oppose
the very cause, which produces it. In the present case it is the
relative motion of the magnet with respect to the coil which is the
cause of the production of the induced current. Hence, the induced
current always flows in such a direct as to oppose this relative
motion (i.e., the approach or withdrawal of the magnet).
Source ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
current flows in the clockwise direction, thus making the face of
the coil (facing the magnet) a S-pole. Therefore, the N-pole of the
magnet has to be withdrawn against the attractive force of the
S-pole of the coil. Again the mechanical energy required to
overcome this force of attraction is converted into electric energy.
It can be shown that the Lenz's law is a direct consequence of law
of conservation of energy. Imagine for a moment that when N pole
of the magnet (Fig.1.16) approaches the coil, induced current flows,
in such a direction as to make the coil face a S-pole. Then due to
inherent attraction between unlike poles, the magnet would be
automatically pulled towards the coil without the expenditure of
any mechanical energy. It means that we would be able to create
electric energy out of nothing, which is denied by the inviolable
Law of Conservation of Energy. In fact, to maintain the sanctity of
this law, it is imperative for the induced current to flow in such a
direction that the magnetic effect produced by it tends to, oppose
the very cause, which produces it. In the present case it is the
relative motion of the magnet with respect to the coil which is the
cause of the production of the induced current. Hence, the induced
current always flows in such a direct as to oppose this relative
motion (i.e., the approach or withdrawal of the magnet).
Source ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
MAGNETIC%20CIRCUITS.pdf
Direction Of Induced EMF
There exists a definite relation between the direction of the
induced current, the direction of the flux and the direction of
motion of the conductor. The direction of the induced current may
be found easily by applying either Fleming's Right-hand Rule or
Lenz's Law. Fleming's rule is used where induced EMF is due to,
flux cutting (i.e. dynamically induced. EMF) and Lenz's when it is
due to change by flux linkages (i.e. statically induced Emf).
Fleming's Right-Hand Rule
“Hold out your right hand with forefinger, second finngure, and
thumb at right angles to one another. If the forefinger represents
the direction of the field, and the thumb represents the direction of
the motion then, the second finger represents the direction of the
induced emf in the coil”.
Fleming's Right-hand Rule can be explained as shown in Figure
Source ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
induced current, the direction of the flux and the direction of
motion of the conductor. The direction of the induced current may
be found easily by applying either Fleming's Right-hand Rule or
Lenz's Law. Fleming's rule is used where induced EMF is due to,
flux cutting (i.e. dynamically induced. EMF) and Lenz's when it is
due to change by flux linkages (i.e. statically induced Emf).
Fleming's Right-Hand Rule
“Hold out your right hand with forefinger, second finngure, and
thumb at right angles to one another. If the forefinger represents
the direction of the field, and the thumb represents the direction of
the motion then, the second finger represents the direction of the
induced emf in the coil”.
Fleming's Right-hand Rule can be explained as shown in Figure
Source ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
MAGNETIC%20CIRCUITS.pdf
Law of Induction
Faraday's Laws
First Law states:
Whenever the magnetic flux linked with a circuit changes, an
EMF is always induced in it. Whenever a conductor cuts magnetic
flux, an EMF is induced in that conductor.
Second Law states:
The magnitude of the induced EMF is equal to the rate of change
of flux-linkages.
Explanation. Suppose a coil has N turns and flux through it
changes from an initial value of 1 φ webers to the final value of 2 φ ,
webers in time t seconds. Then remembering that by flux-linkages
is meant the product of number of turns by the flux linked with the
coil, we have the following relation:
Initial flux linkages = 1φ N . And final flux linkages = 2 φ N
Then the induced EMF is
First Law states:
Whenever the magnetic flux linked with a circuit changes, an
EMF is always induced in it. Whenever a conductor cuts magnetic
flux, an EMF is induced in that conductor.
Second Law states:
The magnitude of the induced EMF is equal to the rate of change
of flux-linkages.
Explanation. Suppose a coil has N turns and flux through it
changes from an initial value of 1 φ webers to the final value of 2 φ ,
webers in time t seconds. Then remembering that by flux-linkages
is meant the product of number of turns by the flux linked with the
coil, we have the following relation:
Initial flux linkages = 1φ N . And final flux linkages = 2 φ N
Then the induced EMF is
Usually a minus sign is given to the right-hand side expression to
signify the fact that the induced EMF sets up current in such a
direction that magnetic effect produced by it opposes the very cause
producing it.
signify the fact that the induced EMF sets up current in such a
direction that magnetic effect produced by it opposes the very cause
producing it.
Source ( pdf )
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
http://faculty.ksu.edu.sa/eltamaly/Documents/Courses/EE%20339/
MAGNETIC%20CIRCUITS.pdf
Subscribe to:
Posts (Atom)
Posts
