International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
www.irjet.net
Regeneration in Variable Frequency Drives and Energy saving Methods Rasin K R1, Arunkumar G2 1MTech in Power Electronics and Drives, VIT University, Vellore, Tamilnadu,India 2Professor, SELECT school, VIT university,Vellore,Tamilnadu, India
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expensive. So it will be beneficial to understand about the basics of regenerative units and to review estimated energy cost
Abstract - When an induction motor is driven by a variable
frequency drive, electric power delivered from the supply is regenerated back while the motor decelerates by applying negative torque to the motor shaft. Energy storage capacity inside the variable frequency drives is usually high limited so energy regenerated should be return back to the grid instead of dissipating as heat .This paper reviews different supply line regeneration options for effective utilization of regenerated power of variable frequency induction motor Drives and a comparison of this methods.
saving. Three types of regenerative power units are available depends on the applications. Basic features and power topologies are explained and compared. Dynamic brake chopper and resistor arrangement is used to convert regenerated power in to heat loss because of low installation cost and simplicity.
1.1 Regenerative converter
Key Words: Variable frequency Drives, Regeneration, Matrix converter, SPWM, Utility cost saving, Regeneration power unit selection.
1. INTRODUCTION Some applications demands operation in a quadrant region where applied torque is in the opposite direction of rotation of Induction motor. The variable frequency Drive must be drive release stored energy from the mechanical load system through the motor terminals to the inverter. This situation faces when the variable frequency drive is trying to break the rotating induction motor, such as the motor inertia starts decelerating or a situation of whenever using loading as in a dynamometer, or when an overhauling holding back . As the Load fed back stored energy to the front end, the main DC bus capacitors of the drive starts charging. The lack of a proper method of utilizing that energy, will leads to continue rise of DC bus voltage to dangerous Level and the drive will get tripped on a fault of Bus over voltage. A method called line Regeneration discharges that energy from the DC bus capacitors and feed it back on the AC utility. The Regenerative power can be dissipated using an arrangement of Brake chopper and Braking Resistor there by the drive will be protected from overvoltage tripping. Also an overvoltage control enabling is available in variable frequency Drives. A significant energy cost saving can be achieved by a regenerative power unit especially in frequent on and off applications, deceleration along with large inertia load, and torque is in overhauling condition. Such applications include decanter centrifuges, hoists, spindle drives, cranes, elevators etc., because of this electricity cost per kilowatt hour is more
Š 2017, IRJET
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Impact Factor value: 5.181
In most of the Drives applications Braking choppers and resistors are used to simply dissipate the power in the form of heat loss. An efficient low budget alternative solution called line regeneration using Regenerative converters that can replace the use of the dynamic braking chopping circuit and external brake resistor network. During regeneration excess regenerative energy available in the inverter front end of variable frequency Drive bypass it to the ac power source through a converter circuit. Figure 1 illustrates how the excessive regenerative energy will feedback from an induction motor to the supply side by utilizing a regenerative converter circuit parallel to the drive inverter circuit , . During motoring mode, the Variable frequency Drives transfer power to the motor terminals without coming the regenerative converter in the picture of main power flow. So during motoring there is no loss in the regenerative converter .When the regeneration taking place, the dc link capacitors starts charging. Regenerative converter will get activated because of regenerative energy
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