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Operation of Electrical Machines (Alternator / Synchronous Generator…
Operation of Electrical Machines
Transformer
Step up or step down ac votages
Number of coils at each side of the transformer indicates increasing or decreasing of current
Equation: NpNs=VpVs
Uses core steel laminators to reduce heat loss
Has oil tank to replace heat oil with cool oil
Rotating magnetic field
ωs= 4πf/p
AC current supply in three winding coil produces rotating magnetic field
ωs= 2πf
Has a north pole and a south pole
Alternator / Synchronous Generator
Produces AC current
Rotating coil or rotating magnetic field
f = (number of poles*rotor speed)/120
Ampere’s Law: Magnetic field produce at the amateur coil as the current flow through it
Faraday’s Law: Moving magnetic field produce alternating EMF
More poles produce slower RPM
Rotor coil assign with DC power source produces magnetic flux
Static amateur coil in stator produces alternating EMF
Induction motor
Faradays' Law: Magnetic field fluctuating, EMF will induce and produce current
Lorentz law: Produce magnetic force, Move the rotor
Iron core is used to make Eddy current loss to minimum
Current is induce in bar of squirrel cage = rotor start to rotate
Solution to energy loss is the addition of fan at the motor
Electricity in inducted in rotor by magnetic induction
SLIP = synchronous speed - rotor speed
Speed of rotating magnetic field = synchronous speed
DC motor
Back EMF directly proportional to speed of motor
Shunt motor
Field coil connected in parallel
Has low starting torque but speed remains constant irrespective of load
Back EMF produced which opposes the input EMF can reduce armature current
Series motor
Field coil in series
Has good starting torque, but speed drops drastically with the increase of load
Converts Electrical energy to Mechanical energy
Lorentz law: When electromagnetic force is induced on it, the coil rotates based on Flemings' Left Hand Rule
More armature loops = smoother motor rotation
DC generator
Consists of magnetic frame with field coils attached. The armature in between is connected to the commutator
Commutator collects current from the armature conductors and converts AC current to DC current
Faraday's Law: When there is a change in magnetic flux with a conductor, emf is induced
Converts Mechanical energy to Electrical energy