Electrical Motor
An Electric motor is a machine which converts electrical input energy into
mechanical output energy.
- When a current carrying conductor is placed in magnetic field, it experiences a mechanical force whose direction is given by Fleming's left hand rule.
- The magnitude of the force experienced by the conductor is given by
F = B I L sin q
Where F = Force in Newton
B = Maximum flux density in Weber/meter2, it
is a vector
quantity
I = Current in Ampere
L = Length of conductor in meter
q = Angle between
position of conductor and direction of
magnetic field.
- When q = 90° ( conductor and magnetic field are mutually
perpendicular ) force produced on the conductor is maximum.
- If q = 0° ( conductor and magnetic field is parallel ) force produced on the conductor is zero.
How does the rotor ( armature ) rotate?
- When the DC supply is given to the motor, a direct current passes through brushes, commutator and armature winding.
- When it passes through commutator, it converts DC into AC.
- Therefore the group of conductors under the influence of N – pole and S - pole carry currents in the reverse direction.
- The two pole DC Motor is shown in the Figure C.
- Let the current in the armature conductors be outward under the influence of N – pole ( Shown by dots ) and inwards under the influence of S - pole ( Shown by Crosses ).
- The direction of force on each conductor can be determined by applying Fleming's left hand rule.
Fleming's Left hand rule
- If the first finger shows a direction of magnetic field and middle finger shows a direction of current, thumbs indicates the direction of force.
- The conductors experience force in the clockwise direction as shown in the Figure C.
- These force collectively produces a driving torque resulting armature rotates in the clockwise direction.
- When the rotor rotates, there is always an equal and opposite torque on the stator that is why it is very important to bolt a motor securely.
very nice site.
ReplyDelete