Three-Phase AC             Three-Phase Synchronous Machines
  Machines Resource 7
    Aims
    • To understand the methods of starting a three-phase synchronous machine
    • To understand the control gear requirements for a three-phase synchronous 
     machine
                            
  Three-Phase AC                 Three-Phase Synchronous Machines
  Machines Resource 7
    Objectives
     • To be able to explain why a synchronous machine is not self starting 
     • To be able to describe how to start a three phase synchronous machine 
        with a prime mover 
     • To be able to describe how to synchronise a three phase synchronous 
        machine to the mains supply 
     • To be able to describe how to start a synchronous machine with a pony 
        motor 
                                
                      Starting Problems
    A three-phase synchronous machine cannot self start as a motor
       • Stator field moving at 50Hz
       • Rotor field energised with DC via slip rings
       • Stator field moving too quickly for rotor to lock on
                               
                    Prime Mover Method
    Start the machine as a generator using a prime mover and the three-lamp method
                             
                       Prime Mover Method
     Start the machine as a generator using a prime mover and the three-lamp method
    Generator output must match 
     the supply in 3 ways
   • The frequencies must be equal
   • The line voltages must be 
     equal
   • The phase-relationships be the 
     same