Combined April and May 2007 Monthly Report B5.1 Development of a Reliable, Efficient, Lightweight and Compact Cryocooler Combined April and May 2007 Monthly Report PI: Dr. Louis Chow Co-PIs: Drs. Jayanta Kapat, Thomas Wu and Faissal Moslehy Postdoc: Dr. Lei Zhou Graduate Students: Shaohua Lin and Gavin Barnes Principal Authors: Dr. Lei Zhou and Shaohua Lin

Project overview Compressor Rotor design completed Rotor with attached impeller and embedded magnet. Rotor-dynamic analysis confirms critical speed > 160k RPM Motor design completed Stator, magnet and winding are ordered Motor controller hardware is acquired Motor controller software development has started Compressor test rig structure design completed Detailed compressor structural design completed in 3-D model with Pro/E Prepare detailed 2-D drawings of parts for machine shop

Motor and controller design SECTION I Motor and controller design

Digital Control Design of PMSM Principles Implementation

Principles Open Loop V/f Control Block Diagram of the V/f Controller Driver Circuit Conclusion

Main Idea of V/f Control Neglect the winding resistance is flux linkage per phase The goal is to maintain a constant voltage to frequency ratio

Ideal V/f Control Profile

Actual V/f Control Profile

Block Diagram of Controller

Driver Circuit DC to AC inverter Va M1 on t M2 on

Pros and Cons of open loop control easy to implement Cons: no feedback, unstable compared to closed loop control

Implementation of Open Loop V/f control Using SD Ez DSP 2812 board

Hardware Features TMS320F2812 Digital Signal Processor in socket operating at 150 Mhz. 18 K on chip RAM 128 K on chip FLASH ROM 64 K words on board RAM Expansion Connectors (unpopulated) Onboard embedded IEEE 1149.1 JTAG controller +5 volt operation with supplied adapter Onboard IEEE 1149.1 JTAG emulation connector Compatible with eZdsp Wire Wrap Prototype Card

Software Features Compatible with C2000 Code Composer from Texas Instruments (Includes 'C' compiler, assembler, linker, debugger)  Compatible with SD Flash programming utility from Spectrum Digital

Program Flow Chart

Code Composer Studio Setup

Code Composer Studio Setup Workspace

Main Function of the Control Program

SECTION II Compressor design

Compressor assembly appearance Top cover Inlet Base Board

Compressor assembly appearance Outlet Bearing support Bearing

Compressor structure De-swirler and diffuser Impeller Bearing Outlet volute chamber Motor wire and cooling channel Intake volute chamber stator

Base board and frames (I) Dwelling hole Outlet frame Inlet frame Bolt holes

Base board and frames (II) Compressor base holes Frame bolts Dwelling hole

Base board and frames (III) Material: carbon steel Functions: Provide sturdy support of compressor rotor Provide accurate tip-gap controls Features: High stiffness support Self-aligned Dwelling holes and pins provide high assembling accuracy

Rotor design Material: Impeller attachment: Total length: 107mm High stress stainless steel Impeller attachment: Tight fit Total length: 107mm Span length: 99mm Shaft diameter: 18mm Impeller diameter: 51mm Critical speed: >160k RPM Permanent Magnet

Threaded for seal cover Bearing housing Threaded for seal cover Material: Brass Features: Dwelling holes ensure high alignment accuracy Brass provides good heat spreading and wear resistance Side threads for seal cover to ensure compressor’s complete sealing Attach water cooling accessory for bearings if necessary Dwelling hole Bolt holes

Main sub-assembly (I) Bolt hole dwelling hole Main sub-assembly includes all the major functional components of the compressor This sub-assembly will be installed into the base-frame with dwelling pins and bolts Bolt hole dwelling hole

Main sub-assembly (II) Inner structure of the main sub-assembly Motor stator and wire Diffuser Impeller Intake volute Outlet volute Rotor and bearing 5 4 2 1 3 6

Assembling procedure (I) Fixing the frames on the base board is the first step to assemble the compressor Base bolts

Assembling procedure (II) Insert the main sub-assembly into frame and insert the bearing support at both sides Insert the dwelling pins and tighten the bolts

Final assembly 5.9 inch 6.1 inch 4.9 inch Place the top cover with bolts to finish the assembling

Future work Develop and test open-loop controller codes Deliver compressor parts drawings to machine shop Develop new de-swirler and diffuser