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Speed Control of Induction Motor using Variable Frequency Drive
The document discusses the optimization of auxiliary power at thermal power plants through the implementation of Variable Frequency Drives (VFDs) for 3-phase induction motors. It covers aspects such as energy efficiency, pollution control, and the mechanics of draft maintenance. The simulation and calculations provided indicate significant potential for power saving and operational efficiency improvements by utilizing VFD technology.
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Speed Control of Induction Motor using Variable Frequency Drive
- 1. Optimization of Auxiliary Powerat Thermal Power Plant using Variable Frequency Drive (VFD)
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- 3. Aspects of Project Analysis of AuxiliaryPower Crux of Excessive Power Consumption Scope of Power Saving Introduction Of Variable Frequency Drive for 3 phase Induction motors Power saving and simulation model of VFD
- 4. Power required torun various pumps and motors Power required for the instrumentation and control room Power required to charge the unit and station buses Power required to run the basic auxiliary and necessary equipment’s for the starting and subsequent operation of Power Apparatus Auxiliary Power
- 5. Auxiliary Power BFP, 4000kW ID Fan, 1300kW PA Fan, 1250kW Secondary Crusher, 750kW FD Fans, 750kW CE Pumps, 600kW Conveyer Belts, 280kW Primary Crusher, 225kW
- 6. Induction Motor • SinglyExcited • Runs at constant speed, constant torque, constant slip at fixed frequency • Speed can change if frequency changes • Torque is given as 2 2 2 22 2 3 ( ) TH ind s TH TH V R sR R X X s
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- 8. Induction Motors atThermal Power Plant Use: • Reciprocating Pumps • High Pressure Pumps • Boiler Feed Pumps • Compressors • Draft Fans
- 9. Need of OptimalDraft • Draft is a negative pressure that has to be maintained between stacks and boiler • Dependency on Load Factor • To improve the efficiency of Rankine Cycle • To reduce the carbon foot print • To improve the boiler efficiency
- 10. How Negative Draftis Maintained? • By controlling the flow of flue gases. 1) By varying the speed of Motor 2) By varying the cross section through which gases are being passed away • Dampers are used to control the flow.
- 11. Dampers • Provides thenegative draft proportional to the flue gases produced • Installed at the outlet of pump • Are operated as per the load demand • Controlled by Servo Mechanism • Control signal is calibrated with Electro Governing System
- 12. Energy consumption andDampers With varying position of dampers current drawn by motor varies. As load increases, flue gases increases
- 13. Variation in DamperOpenings with Flow
- 14. Variable Frequency Drive Machine PowerElectronics Measurement Control System
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- 17. Options for VariableFrequency Grid Frequency Generation of Variable Frequency AC by using Inverter
- 18. Schematic Approach ofVFD • Inverter is used to generate the 3 phase power supply that is fed in the 3 phase IM • Frequency of inverted 3 phase supply is controlled by controlling the firing angle of respective switching device • Thus by varying the frequency speed of motor is varied
- 19. Firing Angle Control •Redirecting the Electro Governing Signal • Calibration of externally excited source with the load demand • Measurement of flow and electrical analogous signal corresponding to that flow • Thermocouple interfaced with RTD’s in a balanced bridged circuit • Capacitive transducer that responds against the flow and density • PLC interfacing with the Load Curve Response
- 20. Characteristics of VFD V= K * f * F V is Voltage across induction motor f is supplied frequency to motor F is flux K is constant Without VFD With VFD Motor Speed Constant Variable Damper Position Variable Constant
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- 22. Program for PowerSaving
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- 25. Output from Inverter(Variable frequency with test signal)
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- 27. VFD Executed MotorResponse
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Editor's Notes
- #5 Among all these kind of auxiliaries last one was of my interest, because it contains all the motors where substantial amount of energy or power can be saved by means of some techniques.
- #6 Last one contains the 3 phase induction motors and they draw a significant amount of power at their MCR irrespective of the load demand.
- #9 Mechanical shaft of all these pumps are driven by the rotor shaft of Induction Motor. But at every time these pumps are not required to run at the full load. Their effect has to be maintained. This can be done either by varying the speed or varying the flow or pressure that is being created by the running motor.
- #11 Since speed of motor is constant, there by providing the constant torque and thrust to flue gases. Thus the only option left and that is the variation in cross section.
- #14 As flow increase, pressure at one side of the fan increases but to maintain a negative draft, pressure at other side has to be increased. This is possible if flow is increased and this is achieved by setting the damper position at highly opened.