email@example.comBasis ofVector Control in AC DrivesPresentation byPrashob P Kin.linkedin.com/in/prashob7
firstname.lastname@example.orgVFD or AC Drive• VFD stands for Variable Frequency Drive• VFD is used for speed control of AC motors• The Hardware components of VFD compriseof1. A Converter section with convert AC TO DC2. A Inverter Section which convert DC back to AC of which frequencycan be varied within in a range3. Control card or Control circuit4. Input output interface for controlling the operation of the VFD5. Optional Communication cards or interfaces
email@example.comSpeed Control Schemes Employed inVFD• There are mainly two type of control schemesemployed1. V/F controlIn this output AC maintain a ration between Voltage andCurrent.V/f or V/Hz is the basic control scheme employed in AC drivesand is used for Pump applications mainlyIn V/f control, current is controlled only based on fault orover current level.
firstname.lastname@example.orgVector Control• Two closed loop controls :-Current loop and Speed loop• Using Mathematical vectors drive can separatetoque producing current from magnetizingcurrent• Vector control can tune themselves to the motorafter getting basic motor name plate parameter• Tuning also known in certain cases asoptimization or auto tuning
email@example.comAuto tuning• Auto tune feature measure several variable ofmotor like resistance , inductance of rotor andstator, slip• Based on these values mathematical motormodel is setup and thus controls loops areexecuted at their best• New age drives have adaptive tuning featurewhich is active continuously as the motor runs
firstname.lastname@example.orgWhat are the additional configurations in Vectordrive compared to that of normal V/f drives?• A feedback circuit with at least two current feedbacks fromthe motor leads• With above configuration vector drives are capable of“encoder less operation”, however there is provision toprovide encoder/resolver feedback• More powerful controller to perform vector analysis oncurrent and voltage feedback
email@example.comAdvantages of Vector Control• Vector control can deliver 100% torque form 0 to ratedspeed• Speed control is more precise than that of V/F• Since closed loop control is excellent, vector control canbe implemented were PID loops or set point iscontinuously coming from a process feed back or othersystems• This control is suitable for applications involving1. Torque control2. Basic position control[advance control require servo drives]3. Electronic gearing , pulse following4. Tension control with dance adjustment etc