Driving Low Voltage High Speed BLDC Motors Above 1 KW Gary Box Software Defined Power www.softwaredefinedpower.com
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Driving Low Voltage High Speed BLDC Motors Above 1 KW
Gary Box
Software Defined Power
www.softwaredefinedpower.com
The Case For Speed
• Smaller Size Per HP
• Lower Weight
• High Pole Count Configurations
• System Design Flexibility
Challenges of High Commutation Speed Motors
•High Speed = Low Kt = Low # Turns = Low Inductance
•Ripple Current Dilemma.
•I**2*R losses•Hysterisis Losses
The Downside of the Conventional Inverter
• Inverter Carrier Frequency Must Be Increased
• Increased Hysteresis loss
• Increased Eddy Current Losses
• Higher switching losses in the Inverter
• Increased EMI Footprint
A Solution;The Two Stage Converter
BUCK/ BOOSTCONVERTER
3 PHASECOMMUTATOR
CONTROL
MOTORDC IN
VARIABLEDC MOTORVOLTAGE
A Little History• The “Thyratron Motor” (Alexanderson and Mittag, 1934)
A 21st Century Implementation
MULTIPHASEBUCK/ BOOST CONVERTER
3 PHASECOMMUTATOR
TMS320f28XXXMICROCONTROLLER
MOTORDC IN
VARIABLEDC MOTORVOLTAGE
What’s New?
• Multiphase Buck/ Boost Operating at 100Khz+
• Complete Digital Control
• New Device Compatible– SiN for High Performance Low Voltage
– SiC for High Performance High voltage
Multiphase Buck Boost Operation
DC IN DC OUT
PHASE A
PHASE C
PHASE BL1 CURRENT
L2 CURRENT
L3 CURRENT
L1
L2
L3
Motoring
Regeneration
Commutator
2 Stage Controller Advantages
• System Block Location Flexibility
• Fully Digital Intelligent Control
• Scalability
• Software Common Across Different Power Levels
• Improved EMI Footprint
The 3KW Proof of Concept
• Target Motor– Ke = 8.6 V’KRPM
– R = .005 Ohm Line to Line
– L = 2.7uH Line to Line
Motor would require 400Khz PWM for 20% current ripple with conventional inverter.
6 Phase 36V 3KW Controller100 KHZ 20AMP 100V
PHASE MODULE
100 KHZ 20AMP 100VPHASE MODULE
100 KHZ 20AMP 100VPHASE MODULE
100 KHZ 20AMP 100VPHASE MODULE
100 KHZ 20AMP 100VPHASE MODULE
100 KHZ 20AMP 100VPHASE MODULE
450 AMPCOMMUTATOR
TIDELFINO
DEMO BOARD
DC IN
PHASE U
PHASE V
PHASE W
MOTOR STATOR
COMMUTATIONENCODER
BIASPOWER SUPPLY
3KW 36V TWO STAGE CONTROLLER
100KHZ 20A Phase Module
Results
TWO STAGE CONTROLLER TEST RESULTS
INPUT VOLTAGE
INPUTCURRENT
INPUTPOWER
DC LINKVOLTAGE
MOTOR SPEED
MOTORCURRENT
36 5.1 183.6 10.12 1000 2036 10.5 378 10.44 1000 4036 22.3 802.8 11.08 1000 8036 9.4 338.4 18.72 2000 2036 19.5 702 19.04 2000 4036 39.5 1422 19.68 2000 8036 13.5 486 27.32 3000 2036 27.6 993.6 27.64 3000 4036 56.5 2034 28.28 3000 8036 17.2 619.2 34.2 3800 2036 35 1260 34.52 3800 4036 78.1 2811.6 35.288 3800 88
Scaling and Alternatives
• The Buck/ Boost First Stage Scales Well Below 3KW and Motor Currents Under 100 Amps
• At 3KW and Above, Another Approach, the Resonant DCDC Converter Becomes More Practical.
MULTIPHASE RESONANT CONVERTER SPECS
• INPUT VOLTAGE 18 TO 32 VDC, 28V NOMINAL
• OUTPUT VOLTAGE 10X INPUT, 280V NOMINAL
• MAX INPUT CURRENT 130 AMPS
• POWER CAPACITY 3600 WATTS CONTINUOUS
• EFFECIENCY 93%
• SIZE 6X6X6 INCH CUBE
• POWER DENSITY 28KW/ CU FT
SOFTWARE DEFINED POWER
Harnessing the muscle of modern power electronics to the intelligence of embedded
control to create a greener world
www.softwaredefinedpower.com
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