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Self excited induction generator as an auxilary brake
- 1. Self-Excited Induction Generator as an Auxiliary Brake
- 2. Contents • Introduction • Braking systems in vehicles • Self excited induction generator • Regenerative braking • Proposed auxiliary brake • Experimental results • Conclusion • References 2
- 3. Introduction • Brake –main system for driver safety • Heavy vehicles need high braking torque and high reliability • Risk of brake fade down the slope • Retarder braking system proves effective Types • Engine compression retarder • Engine exhaust retarder • Engine hydraulic retarder • Electric retarder 3
- 4. Electric Retarder Brake • Placed within drive train • Augment frictional braking system • Serve to slow and maintain steady speed for heavy vehicles • Increasing service life of frictional brakes 4
- 5. Electric Retarder Brake…. • Eddy current brake • Conventional ERB require dc control power • Some- self excited ERB employs permanent magnets • Proposing a self excited ERB without permanent magnets • SEIG+ Electric retarder =auxiliary brake!! 5
- 6. Self excited ERB 6 Shaft/Rotor SEIG Retarder Stator Stator StatorStator Current
- 7. Self Excited Induction Generator 7
- 8. SEIG… • Induction motor made to run above Ns • Slip negative • Delta connected capacitor bank for the supply of reactive power • Takes reactive power -Delivering active power • The stator flux induces currents in the rotor, but since the opposing rotor flux is now cutting the stator coils 8
- 9. Required capacitance of SEIG 9 a= per unit frequency b=per unit speed 2 3 1
- 10. Required capacitance of SEIG.. 10
- 11. IM SEIG Induction Motor Induction Generator SEIG 11 Prime mover run at N>Ns Reactive power taken from supply line Prime mover run at N>Ns Reactive power supplied by capacitor bank
- 12. Advantages of SEIG as auxiliary brake • Efficiency in braking system is not important • Can be controlled by simple circuits • Regenerative braking • Robust 12
- 13. Regenerative Braking • Earlier K.E Heat energy • Energy recovery mechanism: K.E Usable energy • Electric motor Electric Generator (running) (braking) • Delhi metro reduced CO2 emissions 13
- 15. Limitations of Regenerative braking Used in conjunction with Friction based braking • Effect drop off at lower speed • Need Backup • Effective when sink is not fully charged • Power on some wheels • Poor emergency braking performance 15
- 17. SEIG 17 • Capacitor exciting current IG Capacitor V Exc.current • Voltage buildup continues till Xm gets saturated • Without load : Is=Ic • With load : Is=Ic + IL • Load current control strategy to control braking torque
- 18. Control System - Load • Rectifier , Control signal generator, Load impedance , Switch • Rectifier Half wave rectifier dc voltage value=peak value of induced emf Self excited voltage very high Low CRect rectified voltage will vary highly High CRect Voltage build up time increases 18
- 19. Control System… • Load impedance RL+jXL limits load current during switched on When switched off , load current flows through F.D High frequency switching with help of control signal gen.is used • Control signal generator Schmitt trigger control switching frequency RC1 and RC2 create a raw control signal with low voltage Large Cc2 fswitch 19
- 20. Control System… • Switch Power MOSFET used to control load current IGBT not used as it needs negative V to switch off • Interface for Battery charging converter Scope for both power regeneration and braking torque System cost increases Problem arises when battery is fully charged 20
- 22. Results 22
- 23. Results… 23
- 24. Conclusion • Introduced SEIG as a brake and simple control circuit is proposed • Controller does not need ECU thus cheap • Since point meter has constant value , controller is stable • Operating principle and control strategy is verified in Exp. Model • Modifications in main devices in control circuit ,controlling a scaled up retarder becomes possible 24
- 25. References • “ Self-Excited Induction Generator as an Auxiliary Brake for Heavy Vehicles and Its Analog Controller"by Jae-Nam Bae , in IEEE transactions on industrial electronics ,vol,62,no 5,May 2015 • IEEE journal on”Capacitance requirements of self excited induction generators”by T F Chan in IEEE Transactions on Energy Conversion, Vol. 8, No. 2, June 1993 • Electrical Machines II by U A Bakshi and M V Bakshi • Wikipedia 25
- 26. 26 THANK YOU
Notes de l'éditeur
- RETARDERS The exhaust pipe of the vehicle is restricted by a valve. This raises the pressure in the exhaust system, forcing the engine to work harder on the exhaust stroke of its cylinders, so again the engine is acting as an air compressor, with the power required to compress the air being withheld from the exhaust pipe, retarding the vehicle. Diesel engines regulate power output purely by the volume and timing of fuel injected into the combustion chambers. Electric retarders use electromagnetic induction to provide a retardation force.
- When retardation is required, the electrical windings in the stator receive power from the vehicle battery, producing a magnetic field through which the rotor moves. This induces eddy currents in the rotor, which produces an opposing magnetic field to the stator. The opposing magnetic fields slows the rotor, and hence the axle, transmission or driveshaft to which it is attached.
- The capacitor provides the exciting current required by the induction generator, and the induction generator charges the capacitor to increase the terminal voltage. An increase in the capacitor voltage increases the exciting current to the induction generator. In this manner, the voltage buildup continues until the magnetizing inductance decreases to its saturated value and an equilibrium point is reached
- In order to obtain a stable output voltage, the machine must operate at an appropriate level of magnetic saturation. Accordingly, the magnetizing reactance X, is not constant, but varies with the load and circuit conditions. For successful voltage build-up, the load-capacitance Combination should result in a value of X,, which is less than the unsaturated value, hence the capacitance below which the SEIG fails to self-excite.
- Conventional vehicles use frictional braking and dissipate kinetic energy in the form of heat energy into the surroundings When driver applies brake motor switches to generator mode and converts atleast a portion of K.E to electrical energy
- The capacitor provides the exciting current required by the induction generator , and the induction generator charges the capacitor to increase the terminal voltage. An increase in the capacitor voltage increases the exciting current to the induction generator. In this manner, the voltage buildup continues until the magnetizing inductance decreases to its saturated value and an equilibrium point is reached. Once the voltage has built up, a load can be connected to the SEIG. In an SEIG that operates without a load, the stator and capacitor currents are equal. However, in a loaded SEIG, the stator current is divided into the capacitor and load currents . This process means a decrease in the capacitor current ,which is the exciting current, and thus, the induced voltage and braking torque decrease. Therefore, a load-current control strategy, which is the same as a voltage control, can be applied to this system to control the braking torque
- The switch is turned on when the induced voltage is higher than a reference voltage, which results in the decrease in the induced voltage. On the other hand, the switch is turned off when the induced voltage is smaller than the reference voltage, which results in the increase in the induced voltage due to self-excitation.