New eBook on Variable Frequency Drives published By Abhisam Software

Top Quote 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
    QuoteThe easiest guide to Variable Frequency Drives that I have ever readQuote
  • (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.

    VFDs, VSDs, ASDs, VVVF Converters, Inverters
    AC Motors
    An ac induction motor
    Speed Control of ac induction motors
    Power, Speed and 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
    Possibility of replacing DC drives with AC VFDs
    Disadvantages of VFDs
    Cannot be used with all motors
    Distance limitations
    Industrial applications of VFDs

    Inside a VFD
    Overall design
    Rectifier Block
    DC Link block
    Inverter block
    Controller block
    VFD parts & VFD components
    VFD Components
    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
    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

    Starting/Stopping of the motor
    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

    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

    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
    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

    VFDs used in a process plant
    Detailed Implementation of the above
    Digital Communications
    Need for digital communications
    Functions of a typical digital network
    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

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