Explanation of Left and Right Hand Rules Rotating Magnetic Field in 3 phase Induction Motor

1. Fleming Right Hand Rule
If a current carrying conductor placed in a magnetic field, it experiences a force due to the
magnetic field. On the other hand, if a conductor moved in a magnetic field, an emf gets
induced across the conductor (Faraday's law of electromagnetic induction).
Fleming's right-hand rule (for generators) shows the direction of induced current when a
conductor attached to a circuit moves in a magnetic field. ... The thumb is pointed in the
direction of the motion of the conductor relative to the magnetic field. It can be used to
determine the direction of current in a generator's windings
Fleming's right hand rule states to hold the forefinger, middle finger and thumb of right
hand mutually perpendicular to each other so that the forefinger points in the direction
of external magnetic field and thumb points in the direction of motion of conductor. Now
the direction in which the middle finger is pointed gives the direction of induced current
in the conductor.
Fleming's right hand rule is used to determined the direction of induced current (in turn
induced voltage polarity) in the conductor when a conductor moves in a region of
magnetic field.
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2. Fleming Right Hand Rule
How to remember Fleming’s Right hand rule?
Method 1: Relate the thumb with thrust, fore finger with field and center-finger with current as explained
below.
The Thumb represents the direction of motion of the conductor i.e. velocity
The Fore finger represents the direction of the magnetic Field.
The Center finger (middle finger) the direction of the Current or induced emf.
Method 2: Relate the Fleming’s right-hand rule with eBv . Here, e for voltage induced (or induce current), B
is the symbol of magnetic flux density and v is the velocity (direction of motion of conductor). Attribute
these letters e,B,v to the middle finger, fore finger and Thumb respectively.
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3. Fleming Right Hand Rule
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4. Fleming Left Hand Rule
According to Fleming's left hand rule, if the thumb, fore-finger and middle finger of the left
hand are stretched to be perpendicular to each other and if the fore finger represents the
direction of magnetic field, the middle finger represents the direction of current, then the Thumb
represents (Force induced) i.e. direction of motion of the conductor.
How to remember Fleming's left hand rule?
Method 1: Relate the thumb with thrust, fore finger with field and center-finger with current as
explained below.
The Thumb represents the direction of Thrust on the conductor (force on the conductor).
The Fore finger represents the direction of the magnetic Field.
The Center finger (middle finger) the direction of the Current.
Method 2: Relate the Fleming's left-hand rule with FBI (wait! NOT with the Federal Bureau of
Investigation). Here, F for Force, B is the symbol of magnetic flux density and I is the symbol of
Current. Attribute these letters F,B,I to the thumb, first finger and middle finger respectively.
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5. Fleming Left Hand Rule
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6. Magnetic field caused by current in a wire (Curl the Fingers Rule)
The right hand rule states that, to find the direction of the magnetic force on a positive
moving charge, the thumb of the right hand point in the direction of v, the fingers in
the direction of B, and the force (F) is directed perpendicular to the right hand palm.
You can find it by pointing your right thumb in the direction of the current in the wire
and curling your fingers. Your fingers will be curled in the same direction as the magnetic
field around the wire.
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10. Rotating Magnetic Field
The production of Rotating magnetic field in 3 phase supply is very interesting. When a 3-phase winding is energized from a 3-
phase supply, a rotating magnetic field is produced. This field is such that its poles do not remain in a fixed position on the
stator but go on shifting their positions around the stator. For this reason, it is called a rotating field. It can be shown that
magnitude of this rotating field is constant and is equal to 1.5 maximum magnitude of flux where is the maximum flux due to
that current which carries peak current.
A three phase induction motor consists of three phase winding as its stationary part called stator. The three phase stator
winding is connected in star or delta. The three phase windings are displaced from each other by 120°. The windings are
supplied by a balanced three phase ac supply.
The three phase currents flow simultaneously through the windings and are displaced from each other by 120° electrical. Each
alternating .phase current produces its own flux which is sinusoidal. So all three fluxes are sinusoidal and are separated from
each other by 120°. If the phase sequence of the windings is R-Y-B, then mathematical equations for the instantaneous values
of the three fluxes ΦR , ΦY ,ΦB can be written as,
ΦR = Φmsin(ωt)
ΦY = Φmsin(ωt - 120)
ΦB = Φmsin(ωt - 240)
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Rotating Phasor due to 3 Phase ac Supply