The Design of High-Speed High-Power Density Machines

Liping Zheng

TasksDesign 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.

LDT

LDT

LDT

LDT

rr

rr

5.2

2

5.200

300

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.

LD30

Electrical Constraints

Current density

Induced voltage

Output power

Output torque

)/(2 11111 cuASINmJ

wph kfNE 12)2/1(

cos11VImPout

LDT 300

ug kfJB )()28/( 010

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.

)(0 f

0/DDi0

30 /TLD

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) 1000 3000

Radial Flux

Motor

Stator Outer Diameter (in) 1.95 1.95

Length (in) 0.608 1.823

Axial Flux Motor

Rotor Outer Diameter (in) 1.442 1.898

Length (in) 1.406 2.217

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.