Content 3 Content Page 0 Introduction ......................................................................................................................................... 7 0.1 Speed Control of Electrical Motors ....................................................................................... 7 0.2 Why use Speed Control? .......................................................................................................... 8 0.3 How to Adjust the Motor Speed ............................................................................................
8 0.4 Frequency Convereters .............................................................................................................
9 1 Electric Motors ...................................................................................................................................10 1.1 Overview ......................................................................................................................................10 1.2 Fundamentals ............................................................................................................................11 1.2.1 Stator and Rotor .............................................................................................................11 1.2.2 Power and Torque ..........................................................................................................12 1.2.3 AC and DC Motors .........................................................................................................13 1.2.4 Electromagnetic Induction .........................................................................................13 1.2.5 Poles, Synchronous Speed and Asynchronous Speed .....................................14 1.2.6 Effi ciency and losses .....................................................................................................15 1.3 Asynchronous Motors .............................................................................................................17 1.3.1 Rotating Field ..................................................................................................................17 1.3.2 Squirrel Cage Motor ......................................................................................................19 1.3.3 Slip, Torque and Speed.................................................................................................21 1.3.4 Typical Operating Conditions ....................................................................................23 1.3.5 Changing Speed .............................................................................................................24 1.3.6 Motor Nameplate and Star or Delta Confi guration ...........................................27 1.4 Synchronous Motors ................................................................................................................29 1.4.1 Permanent Magnet (PM) Motors ..............................................................................29 1.4.1.1 Back EMF ...........................................................................................................31 1.4.1.2 Torque and Speed Range ...........................................................................32 1.4.2 Brushless DC (BLDC) or Electronically Commutated (EC) Motors ................33 1.4.3 Line Start PM Motor (LSPM Motor) ..........................................................................34 1.4.4 Reluctance Motors .........................................................................................................35 1.4.5 Synchronous Reluctance Motor with Squirrel Cage .........................................36 1.4.6 Synchronous Reluctance Motor (SynRM) ..............................................................37 1.4.7 Switched Reluctance Motor (SRM) ..........................................................................39 2 Frequency Converters ....................................................................................................................41 2.1 Direct Converters ......................................................................................................................41 2.2 Converters with Intermediate Circuit ................................................................................42 2.3 Rectifi er .........................................................................................................................................44 2.3.1 Uncontrolled Rectifi ers ................................................................................................45