AC Variable Frequency Drives

What is this Variable Frequency Drives training course all about?

Explore the world of AC Variable Frequency Drives (VFDs), with our comprehensive e-learning course. Designed to provide a thorough understanding of VFDs utilized across various industries, this course offers a unique and engaging learning experience through a blend of descriptive text, dynamic animations, interactive simulations, and insightful self-assessment tests.

Upon successful completion of the course and passing the associated exam, you’ll be eligible to receive a Certificate of Competency from Abhisam and an electronic badge through Badgr, showcasing your proficiency in VFDs.

About Variable Frequency Drives

Variable Frequency Drives, commonly known as VFDs, have gained immense significance in contemporary times. Once confined to manufacturing industries, they now play a vital role in diverse settings such as commercial buildings, warehouses, and airports. VFDs are a boon for AC induction motors, the backbone of today’s economy. Formerly referred to as ‘constant speed machines’ in traditional electrical engineering literature, AC induction motors can now have their speed and other parameters adjusted, thanks to this revolutionary technology.

What is VFD training? Why Choose this E-Learning Course on VFDs?

VFD training is about training yourself on how to select, install and use VFDs. At Abhisam, we have been pioneers in promoting self-paced e-learning courses tailored for engineering and technical professionals worldwide. Responding to the demand for an accessible and engaging course on Variable Frequency Drives, we’ve crafted an educational experience that combines animations, simulations, photos, and videos. This course provides a vendor-neutral, unbiased exploration of VFD technology, presenting a stimulating alternative to mundane PowerPoint presentations or monotonous lectures. Join us and delve into the realm of VFDs to enhance your knowledge and skills in this transformative field.

Module 1: Basic Concepts

• Introduction
• VFDs, VSDs, ASDs, VVVF Converters, Inverters
• AC Motors
• An ac induction motor
• Speed Control of ac induction motors
• Power, Speed and Torque
• Torque
• Locked Rotor Torque
• Motor characteristics and types
• Design A motor
• Design B motor
• Design C motor
• Design D motor
• Design E motor
• Which type is best for my application?
• Load torque characteristics for different kind of loads
• Classification of loads
• Constant Torque loads
• Variable Torque loads
• Constant Power loads
• Four Quadrant Operation
• Overview of AC motor controls
• DOL starter (Direct On Line starter)/Across the line starter
• Star (Wye) and Delta connections
• Control with a VFD
• Speed Regulation
• Better Power Factor
• Soft Starting
• Flexibility in input power
• Precision Controls for torque and speed
• Energy Saving
• Replacement of control valves in process plants
• Built in PID controls
• Communication
• Possibility of replacing DC drives with AC VFDs
• Disadvantages of VFDs
• Harmonics
• Cannot be used with all motors
• Distance limitations
• Noise
• Industrial applications of VFDs

Module 2: Inside a VFD

• Introduction
• Inside a VFD
• Overall design
• Rectifier Block
• DC Link block
• Inverter block
• Controller block
• VFD parts & VFD components
• VFD Components
• Diode
• Diode Curve
• Switching frequency of diodes
• Rectifier Circuits
• Half wave rectifier
• Full wave rectifier (Bridge rectifier)
• Three phase bridge rectifiers
• Thyristors (Silicon Controlled Rectifiers-SCRs)
• Firing angle
• Three phase rectifier using thyristors
• DC link block
• Soft Charge Circuit
• Inverter Block
• Transistor (BJT)
• Working model of a transistor
• Transistor as an amplifier
• Transistor as a switch
• MOSFET
• IGBT
• Pulse Width Modulation
• How does Pulse Width Modulation work?
• Changing the amplitude of the output
• sinusoidal waveform
• Changing the frequency of the output
• sinusoidal waveform
• Noise effects of PWM inverters

Module 3: VFD Functions

• Starting/Stopping of the motor
• Acceleration/Deceleration
• Ramping
• Speed Limits
• Speed Changing
  a) Using the digital inputs
  b) Using a potentiometer
  c) Using the analog input signal
  d) Using Digital Communication

• Forward/Reverse operation
• Motor Thermal Overload Protection
• Slip Compensation
• Control schemes in VFDs
• Open Loop controls in VFDs
• Closed loop control with VFDs
• V/f Control
• Vector Control
• What is the “vector” in vector control?
• Sensorless vector control
• Flux Vector control (Closed loop)
• Shaft encoders
• Absolute encoders
• Incremental encoders
• Difference between absolute encoder and incremental encoder
• Closed Loop Flux Vector Control
• Field Oriented Control (FOC)
• Comparison between V/f drives and Vector Control drives.
• PID Control
• Anti-windmill protection and Flying Start
• Anti-windmill protection
• Flying Start-Catching up with the motor at power on
• Skip Frequencies
• Torque Control
• Direct Torque Control
• How does DTC work?
• Advantages of DTC
• Disadvantages of DTC
• Motoring and regeneration
• Braking Resistor
• Dynamic Braking
• Line regenerative braking
• DC injection braking
• Motor Overflux braking

Module 4: Energy Savings using VFDs

• Types of Loads
• Pumps, Fans and Blowers
• Traditional flow control
• Control of Centrifugal Pumps
• Affinity Laws of Centrifugal Pumps
• Centrifugal Pump basics
• Pump Characteristic Curve
• System Curve
• Energy savings with fans and blowers
• Other energy savings due to VFDs
• Power Factor improvement
• Reduction in demand charges
• Shorter Duty Cycles

Module 5: Specifying, Selecting and Installing a VFD

• Flowchart
• Load considerations
• Evaluate VFD benefits versus traditional motor controls
• VFD features for maximum benefit
• Derating of VFDs
• Temperature Derating
• Altitude Derating
• Overload Capacity
• Harmonics due to VFD installations
• What are Harmonics?
• Total Harmonic Distortion
• Problems due to harmonics
• What could be the PCC? Says who?
• Measurement of harmonics
• Harmonics in PWM type drives
• Mitigation of harmonics
• Supply voltage
• Number of starts
• Fuse Disconnects
• Bypass circuit
• Installation inside a panel or other enclosure
• Earthing
• Maximum Cable length from VFD to the motor
• IGBT switching
• Standing wave & Reflected wave phenomenon
• Voltage drop
• Long cable length solutions
• Multiple inverters in the same VFD

Module 6: Using VFDs with PLC/ DCS /Control systems

• VFDs used in a process plant
• Detailed Implementation of the above
• Digital Communications
• Need for digital communications
• Functions of a typical digital network
• Profibus
• Modbus
• Safety Aspects
• Summary and Conclusion

Self Assessment Questions

Self Assessment Questions in the course help you measure your own understanding of the subject.

Final Certification Exam

After you complete all modules of the course and pass the exam, you earn a Certificate of Competency in A C Variable Frequency Drives and an electronic badge that you can display on your LinkedIn profile.