variable frequency drives
TRANSCRIPT
VARIABLE FREQUENCY DRIVES
1. What is VFD?2. Purpose Of VFD3. VFD System4. Drive Operation5. Operating Modes6. AC Induction motor7. components8. Advantages9. Function & Features10. Applications.
CONTENTS
Variable Frequency Drives
This technology has several different names such as : • Variable speed drives.• Adjustable speed drives.• Adjustable frequency drives.• Frequency converter.
What is vfd?
• pump and fan applications. • control and regulation. • Speeding up or slowing down a machine or
process.• Protection from overload currents• Safe Acceleration
The Purpose of vfd
A variable frequency drives used in a drive system consisting of the following three main sub-systems:
• AC Motor.• Controller.• Operator Interface.
• In variable-speed applications, a dc motor may be operating in one or more modes:–Motoring. – regenerative braking. –dynamic braking.–Plugging.– four quadrants.
OPERATING MODES
MOTORING
REGENERATIVE BRAKING
DYNAMIC BRAKING
PLUGGING
FOUR QUADRANTS
AC Induction Motor
Three-phase motor operation
• Torque is produced as the induction motor generates flux in its rotating field.
• This flux must remain constant to produce full-load torque.
AC Induction Motor Theory
The speed of the rotating electric field withinthe induction motor.
Synchronous Speed = 120 x frequency no. of motor poles
AC Induction Motor Theory
VFD BLOCK DIAGRAM
• 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
• Vacuum tubes.• Thyristors (SCR’s).• Transistors.
COMPONENTS OF VFD
VFD BASICS
ms.
Pulse-width-modulated voltage and current waveform
• Control of process temperature and pressure.• Maintenance costs can be lower.• Save energy.• Limit the torque
ADVANTAGES
• Set-up Parameters• The Control Method• Acceleration or Accel-Ramp Rate• Automatic Restart• Stopping Method• Automatic Signals
FUNCTIONS & FEATURES
• Water Supply Pump Application• Conveyor Application• Exhaust Fan Application• Compressor Application
APPLICATIONS
• Significant energy savings• Easy setup & programming• Better design• Competitive edge
CONCLUSION