New eBook on Variable Frequency Drives published By Abhisam Software

Abhisam Software is pleased to announce the release of a new ebook on AC Variable Frequency Drives. This ebook can be fully reviewed at the Abhisam Software website via a free trial download. End Quote

The easiest guide to Variable Frequency Drives that I have ever read

(1888PressRelease) October 11, 2010 - Miami - This ebook is meant as an easy guide to any electrical or electronic engineer or technician, or other automation professional who would like to know how modern ac variable frequency drives work. Variable Frequency Drives (VFDs for short), also known by other names such as Variable Speed Drives, Adjustable Speed Drives, Inverter Drives, or simply as VFD drives, are seeing increasing adoption by a host of industries and establishments. The drive towards saving energy costs is a big factor, but so are also other factors such as ease of use, sophisticated functions that allow precise control of ac motors and the ability to hook up these drives to communication networks, industrial control systems such as PLC/SCADA and DCS systems, as well as Building Automation Systems.

Modern industrial society is driven mainly by electrical energy. A large proportion of this electrical energy is used to drive ac induction motors. A properly designed VFD-motor combination can therefore not only offer energy savings, but also result in significantly better controls. These in turn lead to a host of benefits such as productivity improvement, lesser costs and ease of operation and transparency.

Unfortunately, even as VFD technology continues to progress by leaps and bounds every year, the amount of real world, vendor neutral and usable information, that a typical user of VFDs needs, is simply not easily available. There are very few choices-one is either to refer a few published books (which are actually obsolete as they were written years ago), or to depend on the VFD vendors themselves for the information. Another alternative is to search the internet to find nuggets of information here and there, but it is a time consuming process, without any tangible results at the end of the search and also with no guarantee that the information is genuine or trusted.

Hence, to address the need for a comprehensive, detailed, vendor-neutral, technology focused, yet easy to read guidebook on AC Variable Frequency Drives, Abhisam Software has introduced this ebook named as "The Quick Guide to AC Variable Frequency Drives". This ebook covers almost everything that is practically needed for a typical engineer or technician, to understand how VFDs work as well as to select, use and install them. Since this ebook is vendor neutral, the reader can be assured that is completely unbiased.

This ebook is being offered at a very low introductory price of $27 US, so that it is affordable to everybody. To make matters simpler, a free trial of the entire ebook is available for all at the Abhisam Software website.

The ebook is written in a very easy to read style, with plenty of color graphics, diagrams and photos.

The Table of Contents of the ebook is given below.

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
• Inverter Duty Motors
• Advantages of using a VFD for control of motors
• 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

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

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

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

SPECIFYING, SELECTING AND INSTALLING VFDs
• 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

USING VFDS WITH DCS/PLC 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

The Table of Contents given above shows how detailed and comprehensive it is; even though it has been designated as a "quick guide".Everything is explained in very easy to understand language, so that users of VFDs need not feel that they are reading a PhD thesis. The added color diagrams and graphics make reading it a pleasurable experience. A typical technical professional working in a factory or other facility just wants to know how a VFD works, how to specify, select and install a VFD and this is what the ebook does.

To make the buy decision simpler, a full trial preview, that allows the full download of this ebook, is available at the Abhisam Software website.

About Abhisam Software:
Abhisam Software is a knowledge based company engaged in providing e-learning courses, e-books and training for engineers, technicians and other professionals in a diverse range of industries and sectors all over the world. Abhisam Software's courses and ebooks are vendor neutral and purely based on technology, geared towards the end user in mind. For more information please visit www.abhisam.com.

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