Microchip Technology Incorporated · NASDAQ:MCHP
Microchip Technology — Technical Presentation (May 2011)
21 slides from Microchip Technology's technical presentation, May 2011
Slide 1: Regenerative Braking of BLDC Motors
Regenerative Braking of BLDC Motors By Daniel Torres, Applications Engineer Patrick Heath, Marketing Manager High-Performance Microcontroller Division Microchip Technology Inc.
Slide 2: Different electrical braking scheme
Different electrical braking scheme Kinetic Energy Dynamic Braking OR Kinetic Energy Regenerative Braking 2
Slide 3: Regenerative Brake in BLDC motor
Regenerative Brake in BLDC motor Kinetic Energy BLDC Hub Motor used While braking, energy in e-bike application is stored in the battery Regenerative braking stores energy back into the battery, while increasing the life of friction pads on brake shoe. However, to bring the bike to a complete stop,
Slide 4: Configuration of a 3-Phase Rectifier using Simulink
Configuration of a 3-Phase Rectifier using Simulink Continuous powergui Scope + - v 1563 1/9.55 V_AB + RPM RPM to rad /sec - v Diode Diode 1 Diode 2 V_BC + HURST MOTOR - v w V_CA A + i m - B I_A + i V_DC _BUS - Filter C + I_B - v + i - I_C The Hurst BLDC motor running at 1563 RPM, generates the EMF,
Slide 5: 3-Phase Rectifier Simulation Results
3-Phase Rectifier Simulation Results Voltage constant of this motor = 7.24 Vpeak/ Krpm For a speed of 1563 RPM, the voltage = 11.3 Vpeak Filtered DC Bus Voltage 5
Slide 6: MOSFET Bridge as a 3-Phase Rectifier (using Simulink)
MOSFET Bridge as a 3-Phase Rectifier (using Simulink) Scope Continuous powergui 0 0 0 +v - Constant 5 Constant 3 Constant 4 1563 1/9.55 V_AB D D D g g g RPM +v RPM to rad /sec - V_BC Mosfet3 Mosfet4 Mosfet5 +v S S S HURST MOTOR - w V_CA A + -i m B Filter I_A + -i V_DC _BUS C +v I_B - + -i I_C 0 0 0
Slide 7: 3-Phase MOSFET Bridge Rectifier Simulation Results
3-Phase MOSFET Bridge Rectifier Simulation Results Filtered DC Bus Voltage The DC bus voltage results for the 3-phase MOSFET bridge are similar to the rectified 3-phase diode circuit. 7
Slide 8: 4-Quadrant Motor Operation
4-Quadrant Motor Operation Speed Forward I I Braking V V Forward E E Motoring E>V V>E 2 1 Torque Reverse 3 4 |V| > |E| |E| > |V| Motoring V V Reverse E E E Braking I I For a BLDC motor to operate in 2nd quadrant, the value of the back EMF generated by the BLDC motor should be greater than the batter
Slide 9: Energy Flow
Energy Flow Motoring (Current from Battery to Motor) Generating (Braking) (Current from Motor to Battery) For current to flow into battery, the bus voltage should be higher than the battery terminal voltage. Hence we have to boost the voltage developed from motor higher than the battery. 9
Slide 10: Limitation of a Direct Connection
Limitation of a Direct Connection Since this motor is rated for 24-Volts, the battery terminal voltage would be 24-Volts. To generate 24-Volts from the motor (or higher voltage), the motor should run at a speed of 3,400 RPM or higher. Hence we have to figure out ways to boost the back EMF generated
Slide 11: Simple Boost Converter (using Simulink)
Simple Boost Converter (using Simulink) Continuous powergui Boost _Converter The output voltage is Scope proportional to the duty cycle of the MOSFET. Diode Filter V_DC _BUS Series RLC Branch Load +v - V_INPUT v + - DC Voltage Source Pulse g D Generator Mosfet2 S I_DC _BUS i + - 11
Slide 12: Simple Boost Converter Simulation Results
Simple Boost Converter Simulation Results Input voltage = 12 volts DC Boost voltage = 30 volts DC Boost current = 2.5 Amps 12
Slide 13: Boost Converter Based on a 3-phase MOSFET Bridge
Boost Converter Based on a 3-phase MOSFET Bridge BRAKE_MODEL _3 Continuous powergui Scope 2 Scope + - v 0 0 V_AB 0 2000 1/9.55 RPM2 + RPM 1 RPM 3 D D D g g g RPM Gain - v V_BC Mosfet Mosfet1 Mosfet2 + - v S S S HURST MOTOR w V_CA A + -i m B I_A + i Filter V_DC _BUS - C I_B v + + -i - I_C By varying
Slide 14: Boost Converter 3-phase MOSFET Bridge Simulation Results
Boost Converter 3-phase MOSFET Bridge Simulation Results DC Output Voltage ~26 volts @ 2000RPM and 50% duty cycle 14
Slide 15: Boost Converter 3-phase MOSFET Bridge Simulation Results
Boost Converter 3-phase MOSFET Bridge Simulation Results DC Output Voltage ~38 volts @ 2000RPM and 70% duty cycle 15
Slide 16: Picture of Test Setup
S Picture of Test Setup MICROCHIP
Slide 17: Test Result of Boosted Voltage while running Motor at 2500 RPM
Test Result of Boosted Voltage while running Motor at 2500 RPM No Load voltage vs Duty (Tested on Hurst Motor) 50 40 Voltage (V) 2000 RPM 30 2500 RPM 20 3000 RPM 10 0 0 10 20 30 40 50 60 70 80 Duty (%) This slide shows the output voltage of the motor after boost, for different speed and duty cycles.
Slide 18: Test Versus Simulation Results at 2000 RPM
Test Versus Simulation Results at 2000 RPM • For low value duty cycles, the Current vs Duty (Tested on Hurst Motor) boosted voltage is low. Hence no 0.45 current flows into the battery. 0.4 0.35 0.3 • At around 30% duty cycle, the Current (A) 0.25 voltage begins to boost and the 0.2 Series1 0.15 cur
Slide 19: Efficiency Simulation Results
Efficiency Simulation Results Efficiency vs Duty (Simulation) 60 50 Efficiency (%) 40 30 Efficiency (%) 20 10 0 0 20 40 60 80 100 Duty (%) This slide shows the efficiency curve of the brake setup, which gives a maximum efficiency of 55% at 50% duty cycle. Since this is a simulated result, the actual
Slide 20: PID Control for Constant Brake Force
PID Control for Constant Brake Force Required Brake force 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0 0 0 0 0 0 0 0 0 Analog voltage 5 0 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 proportional to the Wheel Speed 20 0 0 0 0 0 0 0 0 0 required brake force 40 0 0 0 0 0 0 0 0 0 60 0 0 0 0 0 0 0 0 0 80 0.1 0.1 0.12 0.12 0.1
Slide 21: Thank You Questions?
Thank You Questions? Note: The Microchip name and logo are registered trademarks of Microchip Technology Inc. in the U.S.A. and other countries. All other trademarks mentioned herein are property of their respective companies. 21
Microchip Technology — Technical Presentation (May 2011) on 6ix