Download - PM-HighSpeed Generator V4
Permanent Magnet High-Speed Generatorfor FTT Micro Turbine
Jinho Kim, Daniel Kirk and Hector Gutierrez
Mechanical & Aerospace EngineeringFlorida Institute of Technology
Performance Requirements
Parameter Power Rating (KW)
Max. Total Weight (kg)
Length(inch)
Stator O.D.(inch)
Speed (RPM)
Temp. Range(F)
Output Voltage,3-PhaseAC(Volt)
Storage (years)
Required 1.2 0.22 1.25 1.3 80k to136k
- 40 to130
180~400 10
Goal 1.8 0.22 1.25 1.3 65k to136k
- 0 to190
180~400 25
Proposed Design
Stator Rotor
Outer Diameter 1.3 inch (33.02 mm) Outer Diameter 19. 625 mm
Inner Diameter 21.625 mm Inner Diameter 6.9 mm
Length 1.25 inch (31.75 mm) Length 1.25 inch (31.75 mm)
Stacking Factor 0.95 Pole Magnet type NdFe35 or SmCo28
Stator Core Material M19-24G Magnet thickness 1.5 mm
Number of Slots 24 Shaft diameter (non-magnetic) 6.9 mm
Air gap (clearance between stator and rotor) 2 mm (air = 1 mm, sleeve = 1 mm).
Machine type: Permanent magnet synchronous generator Number of Poles: 4 Number of Phases: 3 Nominal Speed: 100,000 RPM
Proposed Electrical Layout
Outer core
Inner core Magnet
Shaft
Physical Layout Winding Pattern
Electromagnetic Performance
Permanent Magnet Material NdFe35 SmCo28
Load Line Voltage (RMS) 301.2 V 305.7 V
Line Current (RMS) 2.89 A 2.94 A
Iron-Core Losses 57.2 W 52.3 W
Armature Copper Losses 32.6 W 29.8 W
Total Losses 89.8 W 82.1 W
Output Power 1457 W 1507 W
Input Power 1547 W 1589 W
Efficiency 94.2 % 94.8 %
Rated Torque 0.148 N.m 0.152 N.m
Net Weight 0.154 Kg 0.156 Kg
Simulation by finite element analysis using MAXWELL-AnsoftFour-pole, three-phase design @ 100,000 RPM
Electromagnetic Performance
Output Phase Voltage for NdFeB35, max = 415 V (for SmCo28, max = 402 V)
Air gap flux density for NdFeB35, max = 0.6 T (for SmCo28, max = 0.52 T)
Mechanical Layout in High-Speed Electrical Machinery (18 to 120 kRPM)
U.S. Patent # 5,144,735 (Stark et al.) U.S. Patent # 5,687,471 (Noguchi et al.)
Mechanical Layout in High-Speed Electrical Machinery (18 to 120 kRPM)
U.S. Patent # : 4,625,135 (Kasabian et al.)
Proposed Mechanical Design Permanent magnets bonded to grooves in rotor core Torsional stress in rotor shaft is modest (~ 2.3 MPa) Critical mechanical requirement given by centrifugal forces Containment sleeve required to protect rotor from large centrifugal forces Sleeve made of pre-stressed high-strength material
Containment Sleeve Materials
Aluminum Stainless steel Composite resin
Mechanical strength Low High Medium
Thermal conductivity High Medium Low
Eddy current losses High Medium No
Mass / Inertia Medium High Low
Proposed Mechanical Layout
turbine shaft
permanent magnets (4)
containment sleeve
rotor core
stator
Analysis of Critical Mechanical StressStructural FE analysis of sleeve using ANSYS
Rotational Speed = 100k RPM
Sleeve Material :
AISI Type 302 Stainless SteelTensile Strength, Ultimate 495 MPaTensile Strength, Yield 160 MPa
Sleeve thickness = 1mm
Magnets assumed not bonded or bolted - supported only by sleeve
Max stress at sleeve = 157 MPa
Actual stress would be much less since magnets are bonded and/or bolted
Thermal Analysis
z
r
450 K
Q = R*i^2
Air 300K 50 m/s~300 m/s
FE conduction + convection analysis using ANSYS
Heat source given by stator coils
2-D axisymmetric model
3 cases of air speed
Sleeve thickness = 1mm
Thermal Conductivity:
Stainless steel : 16.2 W/m-K Permanent magnet : 9 W/m-K Copper : 385 W/m-K Carbon steel : 49.8 W/m-K
Air flow = 50 m/s
Air flow = 100 m/s
Air flow = 300 m/s
Results – Temperature Distributions
Thermal Analysis
Layers: shaft (stainless), inner core (carbon steel), magnet, sleeve (stainless), air gap, copper, outer core (carbon steel).
Conclusions
Proposed design meets all electrical requirements Containment of centrifugal forces achieved by pre- stressed sleeve Critical mechanical stresses verified under worst-case conditions Estimated operating temperature ~ 410K Proposed magnetic material (SmCo5) has max service temperature of 523K Loss of nominal magnetic coercivity at the operating temperature ~ 2%
Future Work
Detailed mechanical component design
Detailed 3-D finite-element verification of
Electromagnetic performance
Structural integrity
Thermal analysis – Heat transfer
Analysis / design of electronic power
converter