NORPIE June, Trondheim, Norway Analysis of a PM Machine with Concentrated Fractional Pitch Windings Freddy Magnussen, Dmitry Svechkarenko, Peter Thelin, Chandur Sadarangani

Layout of presentation  Introduction  Torque ripple computation results  Presentation of machine design  Parasitic effects (noise and losses)  Conclusions  Laboratory prototype and measurements  Thermal computation results

Machine design: 14 poles and 15 slots  q=0,36 (number of slots per pole per phase; normally 0,5)  k w1 =0,95 (fundamental winding factor; normally 0,87)  Grain-oriented iron teeth, non-oriented iron yoke  Rectangular copper conductors, c f =0,74

Electromotive force

FEM-computed torque ripple  Pure sinusoidal q-current  no inverter influence  Current loadings: 0, 103, 207, 413 and 827 A/cm (RMS)

Air gap flux density  Armature reaction for the current loading 827 A/cm (RMS)  No-load flux density

Flux density in rotor back (Machine C)  Current loadings: 0, 103, 207, 413 and 827 A/cm (RMS)  Tangential flux density component at 2000 rpm

Radial magnetic stress in air gap  Unbalanced radial forces  noise

Some radial vibration mode shapes

Prototype stator

Measurement results  Low speed high torque : copper loss thermal influence Generator tests Motor tests  High speed low torque : iron loss thermal influence

Thermal computations (I) Aluminium frame Cooling duct Velocity profile Water-cooling cylinder

Thermal computations (II) Max 139ºC Max 86ºC Max 157ºC Max 98ºC [K] Inlet water: 22ºC

Conclusions  High torque density (5,0 Nm/kg)  Low torque ripple  Concentrated winding machines with an odd number of slots and an almost equal number of poles (e.g 8/9, 14/15, 20/21) are sensitive to these parasitic effects:  Unbalanced radial forces  noise  Alternating magnetic fields in the rotor  losses  Cost effective manufacturing process

Thank you!