The Design of High-Speed High-Power Density Machines Liping Zheng

Tasks  Design two kinds of motors (1kW and 3kW) using sizing equations combined with FEM simulation and calculate the machine parameters and performance.  Consider both axial flux and radial flux structure to compare the performance.  To design radial flux motor, use the same rotor and stator diameter for two motors to reduce the manufacture cost.

Sizing Equations  Four types of sizing equations are available which link the motor torque to the motor size.

The Sizing Equation  Provides many relations between physical dimensions and density-like quantities and is well adaptive to produce a design that is geometrically compatible from the start.

Electrical Constraints  Current density  Induced voltage  Output power  Output torque

Maximizing the Coefficient  Specify current density: J1=10000A/in flux density at stator: Bt=1.8T, Bc=1.4T flux density at airgap : Bg=0.8T  Get the maximum value of  Select the number of slots and the winding structure to meet the induced voltage and input current requirement.

Rotor Design  Design the rotor structure using magnetic equivalent circuit method.  4 poles.  High energy PM: NdFeB (Neodymium-iron-boron).  Design airgap length.  Design permanent magnetic structure.

FEM Analysis  Calculate flux density in airgap, rotor and stator core.  Calculate back emf and inductance.  Calculate torque and torque ripple.  Calculate losses.

Performance Analysis  All performance must meet the required specification.  Thermal consideration.  Tradeoff may be necessary for the best performance.

Estimated Results Using Sizing Equations Output Power (W) Radial Flux Motor Stator Outer Diameter (in)1.95 Length (in) Axial Flux Motor Rotor Outer Diameter (in) Length (in) Estimated Design Size for 40Krpm Motor (Case not included) Axial flux motor size parameters are calculated according to the same airgap surface and stator volume as those of the radial flux motor.