variable frequency drive ppt
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Transcript of variable frequency drive ppt
Submitted by
T.VANI SANTHOSHI – 09W91A0252
CH.ASHWINI - 09W91A0217
V.PRIYANKA GOUD – 09W91A0256
D.BASAVESHWAR – 07W91A0208
E.RAVI RAJA - 08W91A0239
Under the guidance of
M.Spandana,M.tech
Asst.Prof, EEE department
Malla Reddy Institute of Engineering and Technology
VARIABLE FREQUENCY DRIVES
A variable-frequency drive (VFD) is a type of adjustable-speed drive
It is used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.
INTRODUCTION
• Systems employed for
motion control are called
drives and may employ
any of the prime movers
such as diesel or petrol
engines ,electric motors,
for supplying mechanical
energy for motion control .
• Drives employing
electrical motors are
known as electrical drives.
ELECTRICAL DRIVES
There are two types of electrical drives mainly
1. DC Drives
2. AC Drives
• DC drives are dc motor control systems
• AC drives are AC motor speed control systems
TYPES OF ELECTRICAL DRIVES
It controls the rotational speed of an AC motor by controlling the frequency of electrical power supplied to motor.
It’s a specific type of adjustable speed drive
What is a VFD
Danfoss Danfoss = First company to = First company to mass produce a.c. variable frequency drives (VFD)mass produce a.c. variable frequency drives (VFD)
EVOLUTION OF VFD
2003 2007
199819931988198319731968
A variable frequency drive generally consists of following:
Ac motor
Main controller assembly
Operator interface
DESCRIPTION OF VFD
It is usually a 3 – phase induction motor.
An AC motor is an electric motor driven by an alternating current.
The magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet.
AC MOTOR
It is a solid state power electronic conversion device. It consists of three main parts
Bridge rectifier
DC link
Inverter
MAIN CONTROLLER ASSEMBLY
It converts AC input power to DC intermediate power using a rectifier or converter.
BRIDGE CONTROLLED RECTIFIER
DC intermediate power is then converted to quasi sinusoidal AC power using inverter switching circuit
DC LINK
It changes DC energy into three channels of AC energy that can be used by AC motor
BASIC INVERTER
The operator interface often includes an alphanumeric display and/or indication lights and meters to provide information about the operation of the drive.
A serial communications port is also often available to allow the VFD to be configured, adjusted, monitored and controlled using a computer
OPERATOR INTERFACE
CIRCUIT DIAGRAM OF VFD
WORKING OF VFD
AC motor characteristics require the applied voltage to be proportionally adjusted whenever frequency is changed in order to deliver the rated torque
BLOCK DIAGRAM OF VFD
There are many methods of control for frequency in variable frequency drives
Among them PWM is mostly used because of its own advantages.
METHODS OF CONTROL
Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches.
PULSE WIDTH MODULATION
VFD’s use their output devices (IGBTs, Transistors, thyristors) only as switches.
They can be classified as
Voltage source inverter fed drives i.e. constant voltage
Current source inverter fed drives i.e. constant current
TYPES OF VFD OF VFD
• Constant voltage converter : intermediate DC link voltage remains constant during each output cycle
• Constant current drives : large inductor is placed between the input rectifier and the output bridge, so the current delivered is nearly constant
CONSTANT CURRENT AND VOLTAGES DRIVES
Cooling of the motor is usually not good in low speed range
.When frequency reaches zero, motor is shut off.
The motor shall require a load reactor and filters if the pump leads from the VFD exceed certain conditions
FACTORS AFFECTING SPEED CONTROL
ENERGY SAVINGS
Example : vfd for centrifugal pumpFlow is proportional to speedPower varies to the cube of the
speed change20% reduction in speed
= 50% reduction in energy
50% reduction in speed
= 80% reduction in energy
VFD controllers designed to operate at 111v volts to 690v are often classified as low voltage units.
Typically designed for use with motor rated to deliver 0.2 k.watts up to several mega watts.
Medium voltage VFD controllers are designed to operate at 2400/4162 volts (60hz), 3000 volts(50 hz )
VFD RATINGS
• VFDs are frequently used to control motors for: Fans, Pumps, Compressors
Mills.
• Oil & Gas, petroleum, petro chemistry: oil transfer pumps, compressors,
pumps, etc.
• Mining: mortar pumps, fans, etc.
• Water and waste water: water supply pump, etc.
APPLICATIONS
Hence variable frequency drives are mainly used because of the following reasons:
• Stable and reliable performance
• Saves energy and therefore reduces energy costs
• Isolated control signal provided by fibre optics between Power cell and Controller
CONCLUSION
QUERIES ???
THANK YOU