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How does machines work? (Transformers (Working principle (Based on…
How does machines work?
Transformers
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What is a transformer?
An electrical machine converts AC electric energy of a frequency at one voltage level to AC electric energy at another voltage level of the same frequency.
Working principle
Based on Faraday's law of induction : 
The primary coil is excited by an AC source, Vp
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An AC voltage, Vs, is induced in the secon coil
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3-phase transformers
Coils configuration
The primary and secondary coils sit concentrically with the low voltage winding in the inside and the high voltage winding on the outside
Connection
The low voltage windings are connected in a delta configuration
The high voltage windings are connected in a delta configuration
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AC Machines
Rotating magnetic field
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If a 3-phase set of currents, each of equal magnitude and different in phase by 120 degrees, flows in a 3-phase winding, then it will produce a rotating magnetic field of constant magnitude.
How?
Two magnetic fields in a machine - one is produced by the stator and the other one produced by the rotor
Torque will be induced in the rotor, which causes the rotor to turn and align itself with the stator's magnetic field.
Synchronous speed
Speed of rotation of the magnetic field :
The higher the number of poles, p, the higher is the synchronous speed
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