Variable frequency drives

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Variable frequency drives

  1. 1. VARIABLE FREQUENCY DRIVES
  2. 2. 1. Whatis VFD?2. Purpose Of VFD3. VFD System4. Drive Operation5. Operating Modes6. AC Induction motor7. components8. Advantages9. Function & Features10. Applications.
  3. 3. Variable Frequency DrivesThis technology has several different names suchas :• Variable speed drives.• Adjustable speed drives.• Adjustable frequency drives.• Frequency converter.
  4. 4. • pump and fan applications.• control and regulation.• Speeding up or slowing down a machine or process.• Protection from overload currents• Safe Acceleration
  5. 5. A variable frequency drives used in a drivesystem consisting of the following three mainsub-systems:• AC Motor.• Controller.• Operator Interface.
  6. 6. • In variable-speed applications, a dc motor may be operating in one or more modes: – Motoring. – regenerative braking. – dynamic braking. – Plugging. – four quadrants.
  7. 7. MOTORING
  8. 8. Three-phase motoroperation
  9. 9. • Torque is produced as the induction motor generates flux in its rotating field.• This flux must remain constant to produce full-load torque.
  10. 10. The speed of the rotating electric field withinthe induction motor.Synchronous Speed = 120 x frequency no. of motor poles
  11. 11. • All VFD’s need a power section that converts AC power into DC power.• This is called the converter bridge.• Sometimes the front end of the VFD, the converter is commonly a three-phase, full wave- diode bridge.• The DC bus is the true link between the converter and inverter sections of the drive
  12. 12. • Vacuum tubes.• Thyristors (SCR’s).• Transistors.
  13. 13. ms. Pulse-width-modulated voltage and current waveform
  14. 14. • Control of process temperature and pressure.• Maintenance costs can be lower.• Save energy.• Limit the torque
  15. 15. • Set-up Parameters• The Control Method• Acceleration or Accel-Ramp Rate• Automatic Restart• Stopping Method• Automatic Signals
  16. 16. • Water Supply Pump Application• Conveyor Application• Exhaust Fan Application• Compressor Application
  17. 17. • Significant energy savings• Easy setup & programming• Better design• Competitive edge

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