Operating Principle of Machine (Electrical Machines)

Operating Principle of Machine (Electrical Machines)

1. Segment 1

   • Transformers
     • - receives AC voltage and delivers it at a lower or higher voltage depending on if it is a step-up or step-down transformer
     • - basic principle behind it is electromagnetic induction or Faraday's Law , which states voltage is induced in a coil when a time-varying magnetic field passes through it
     • - if number of turns of primary > secondary , it is step-down , vice-versa and it is step-up
     • - 3 phase transformer has 2 types of connections , delta and star
     • - AC voltage flows through the primary coil and it creates a magnetic field through the core , that magnetic field then induces a voltage at the secondary coil
   • Rotating Magnetic Field
     • - a magnetic field that has moving polarities and which opposite polarities rotate at a central point
     • - the rotation ideally occurs at constant angular rate , 90 degrees for a two coiled system and 120 degrees for a three coiled system
     • - basic principle behind how an AC motor functions
     • - the polarities depends on the waveform of the AC currents

2. Segment 2

   • Alternator
     • - it consists of 2 main components which are the armature coil (stator) and the salient pole rotor (rotor)
     • - electricity is produced in alternators by electromagnetic induction
     • - a DC power source is connected to the rotor coil and thus creating a magnetic field at the rotor , an external force is then applied on the rotor causing it to rotate along with the magnetic field
     • - this magnetic field then intersects with the armature coils thus inducing an alternating e.m.f through it and thus electricity is generated
   • Indutcion Motor
     • - an induction motor has 2 main parts , a stator and rotor
     • - a 3-phase AC flows through the stator thus creating a magnetic field , and due to the fluctuating nature of AC , the magnetic also fluctuates , and according to Faraday's Law and e.m.f is induced through the loop
     • - there is a current-carrying wire in the magnetic field , and due to Lorentz Law , the loop will start to rotate
     • - electricity is induced in the rotor by magnetic induction rather than a direct supply

3. Segment 3

   • DC Motor
     • - the stator provides a magnetic field and the armature coil of the motor is connected to a DC power supply , and when current flows through the coil and electromagnetic force is induced on it according to Lorentz Law , thus the coil starts to rotate
     • - two types of connections , shunt and series connections
   • DC Generator
     • - uses electromagnetic induction to convert mechanical energy to electrical energy , Faraday's Law
     • - an external force is exerted on the generator to cause the magnetic field to rotate
     • - the commutator converts AC current to uni-directional current

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