Azionamenti elettrici con motori sincroni per trazione. Bianchi_UniPd.pdf · Azionamenti elettrici...

Azionamenti elettricicon motori sincroni

per trazione

Nicola Bianchi

Department of Industrial EngineeringUniversity of Padova

35131 Padova (ITALY)[email protected]

LE PROSPETTIVE DELLA TRAZIONEFERROVIARIA PER GLI ANNI 2020 - 2030

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SynchronousPermanentMagnet Motor

SynchronousReluctanceMotor

The PMassistance

SynchronousIPM Motor

Conclusions

Padova, 17 marzo 2017

Outline

1 Synchronous Permanent Magnet Motor

2 Synchronous Reluctance Motor

3 The PM assistance

4 Synchronous IPM Motor

5 Conclusions

N. Bianchi Synchronous Motor Drives for traction applications 2

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The PMassistance


Conclusions


SynchronousPermanent Magnet (PM)

Motor


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The PMassistance


Conclusions


The synchronous SPM motorhigh torque density,high efficiency,high dynamics.


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The PMassistance


Conclusions


Rare earth PMHigh magnetic energy and high coercive force.

−2000 −1500 −1000 −500 0−2

−1.5

−1

−0.5

0

0.5

1

1.5

Magnetic field (kA/m)

Flu

x d

en

sity

(T

)

20°C140°C sintered

NdFeBN45UH

Ferrite C12


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The PMassistance


Conclusions


Surface Mounted PM motorThe PMs are mounted on the rotor surface


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The PMassistance


Conclusions


Stator and rotor


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The PMassistance


Conclusions


PM glueing and rotor bandage


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The PMassistance


Conclusions


Rotor bandage

for high speed applications


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The PMassistance


Conclusions


Non-overlapped coil toothto reduce the end-winding length (weight and cost).


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The PMassistance


Conclusions


Vector diagramLow leakage inductance Lσ.High power factor cosϕ.Only torque current Iq (no magnetizing current Id ).Lower Joule losses and high efficiency.

d axis

q axis

ie

ve

I

Vφ

Λpmj- IqLσ

IqLj σΛpm

Iq=j

=90°


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The PMassistance


Conclusions


Howeverthere are also some drawbacks.


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The PMassistance


Conclusions


Rotor lossesdue to current time harmonics and MMF space harmonics.


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The PMassistance


Conclusions


Limited flux-weakening operations

No capability of constant-power versus speed operationThis implies an oversize of the inverter VA rating.


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The PMassistance


Conclusions


SynchronousReluctance

Motor


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The PMassistance


Conclusions


The synchronous reluctance (REL) motoris attractive thanks to its

absence of rare-heart permanent magnet,high torque density,fault–tolerant capability.


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The PMassistance


Conclusions


In REL machine:a high permeability path.It is referred to as the direct–axis path.

d

q


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The PMassistance


Conclusions


In REL machine: two different rotor paths for the fluxa low permeability path.It is referred to as the quadrature–axis path.

d

q


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The PMassistance


Conclusions


REL motorThe higher flux linkage along d–axis.

The q–axis flux linkage is limited by the rotor flux barriers.

−6 −4 −2 0 2 4 6−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

Corrente assorbita [Apk]

Flussiconcatenati[Vs]

flusso di asse−qflusso di asse−d


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The PMassistance


Conclusions


The flux linkages can be expressed as

λd = Ld idλq = Lq iq

The rotor saliency is defined asthe ratio between the d– and q–axis inductance:

ξ =Ld

Lq

Average torque

τdq =32

p(Ld − Lq)iq id


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The PMassistance


Conclusions


The REL motor is current controlledId current is the “magnetizing” currentIq current is the “torque” current

d axis

q axis

Id

LdId

Iq

ie

ve

IV

φ

LdIdj

IqLqj

- IqLq

they are combined to get the maximum torque density.N. Bianchi Synchronous Motor Drives for traction applications 21

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Conclusions


Torque map in the Id–Iq plane

Constant torque curve as a function of Id and Iq

0

0.5

1.0

1.5

2.0

0 0.5 1.0 1.5 2.0

q-ax

is c

urre

nt

d-axis current

Motor torque

max TI

(p.u.)

(p.u

.)(p.u.)

0.25

0.5

0.75

1.0

1.25

1.5

1.75

2.0


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The PMassistance


Conclusions


A drawback: the quite low power factor.The voltage vector leads the current vectorof a quite large angle ϕ.

d axis

q axis

Id

LdId

Iq

ie

ve

IV

φ

LdIdj

IqLqj

- IqLq

The volt-ampere ratings of the inverteris 30 to 40 % higher than mechanical output power.


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The PMassistance


Conclusions


Test benchfor measuring torque vs current angle and torque ripple.


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The PMassistance


Conclusions


Experimental resultsAverage torque versus current angle of REL motor.Currents used in the tests are 5 A, 10 A, 15 A and 20 A

non-skewedrotor

skewed rotor


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The PMassistance


Conclusions


REL motor: torque and power versus speedExperimental versus simulated results.


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The PMassistance


Conclusions


Mechanical stress on rotor bridges

Rotor iron bridgesare designed so asto sustain bothmagnetic andcentrifugal forces.


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The PMassistance


Conclusions


The PM assistance


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The PMassistance


Conclusions


PM assisted synchronous reluctance (PMAREL) machineA PM can be inset in the rotor flux–barriers.The aim:

to saturate the rotor iron bridges,to increase the motor torque,to increase the power factor.


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The PMassistance


Conclusions


Rectangular holes have to be considered so asto inset the PM within the rotor flux–barriers

Insertion of the assisting PMs into rotor flux–barriers


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Conclusions


a part of the PM flux tends to saturate the iron bridgesThis implies:

an increase of the torque andan increase of the power factor.

Part of the PM flux flows into the iron bridges.


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The PMassistance


Conclusions


There are advantages in adopting PMs.The PM added along the negative q–axiscompensates the flux linkage LqIq.

d axis

q axis

IdLdId

Iq

ie

ve

I

V

φ

LdIdj- IqLq

mj

IqLqj

m-j

Vector diagram of PMAREL motor.


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The PMassistance


Conclusions


The advantage is twofold.1 An increase of the power factor.

Thus, a PMAREL motor requires lower Volt-Ampererating for given nominal mechanical power.

2 The electromagnetic torque of the motor increases.

A PM torque term is added to the reluctance torqueterm.


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The PMassistance


Conclusions


Air–gap flux density distribution

0 100 200 300 400 500 600 700−0.2

−0.1

0

0.1

0.2

Bn

(T)

The added PM is minimumto maintain the intrinsic fault–tolerant capability.

the back EMF is low,the short–circuit current is lowthe corresponding braking torque is low.


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The PMassistance


Conclusions


PMAREL motor: torque and power versus speedExperimental versus simulated results.


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Conclusions


Drawbackthere is a high torque ripple, if not correctly designed.

Remedial strategies1 rotor skewing (step–skewing);2 suitable choice of the number of flux–barriers,3 shifting of the flux–barriers;4 asymmetry of the flux–barrier geometry.


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The PMassistance


Conclusions


REL motor — Skewing effect on torque ripplemeasured torque versus mechanical position I = 10 A

0 90 180 270 360

11

12

13

Torq

ue[N

m]

θm

[degrees]

non skewed rotor

0 90 180 270 360

11

12

13

Torq

ue[N

m]

θm

[degrees]

skewed rotor


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Conclusions


REL motor — Skewing effect on torque ripplemeasured torque versus mechanical position I = 20 A

0 90 180 270 36022

24

26

28

Torq

ue[N

m]

θm

[degrees]

non skewed rotor

0 90 180 270 36022

24

26

28

Torq

ue[N

m]

θm

[degrees]

skewed rotorN. Bianchi Synchronous Motor Drives for traction applications 38

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Conclusions


Photos of the "Romeo and Juliet" laminations


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The PMassistance


Conclusions


Photo of the "Machaon" lamination


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The PMassistance


Conclusions


Measured torque comparisonsymmetric PMAREL motor

0 90 180 270 3602

2.1

2.2

2.3

Angular position (mechanical degrees)

Tor

que

(N

m)

"Romeo and Juliet" motor

0 90 180 270 3601.8

1.9

2

2.1


Tor

que

(N

m)

"Machaon" motor

0 90 180 270 3602

2.1

2.2

2.3


Tor

que

(N

m)

The resulting torque ripple is about one third.N. Bianchi Synchronous Motor Drives for traction applications 41

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The PMassistance


Conclusions


SynchronousInterior Permanent Magnet (IPM)

Motor


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Conclusions


The PM within the flux barrier is a rare earth PM.Interior PM (IPM) machine.The aim is

the increase of the motor torque,the improvement of the torque vs speed characteristic.


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The PMassistance


Conclusions


An IPM motor for an electric scooterStandard stator.Two flux–barriers per pole in the rotor.


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The PMassistance


Conclusions


A 12–slot 10–pole prototype with non–overlapped coilsand two flux–barriers per pole in the rotor.


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The PMassistance


Conclusions


Picture of the rotor lamination

In fractional-slot winding machinesthe reluctance torque component is reduced

The dominant torque component is due to the PM flux.


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The PMassistance


Conclusions


Picture of the rotor laminationIPM motor lamination for naval propulsion system


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The PMassistance


Conclusions


Fractional–slot winding with non–overlapped coilsallows a physical separation between the phases.

A dual–three phase fractional–slot IPM machineis characterized by two identical windings,each supplied by a separate inverter.


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The PMassistance


Conclusions


To achieve a smooth torque is a challengein fractional–slot machine with anisotropic rotor.

2

1

3

45

6

7

8

9

10 11

12

2

1

3

45

6

7

8

9

10 11

12

Two-layer winding Four-layer winding

It is also possible to optimize the windingadjusting the number of conductors of the coilsso that specific harmonics can be canceled.


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The PMassistance


Conclusions


The torque ripple results to be always lower than 5%,regardless to the adopted trajectory.


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The PMassistance


Conclusions


Conclusions


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The PMassistance


Conclusions


Synchronous SPM motor:Advantages:

high torque density,high efficiency

Drawbacks:expensive PMs,no suitable for Flux-weakening.


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The PMassistance


Conclusions


Synchronous REL motor:Advantages:

robust and cheap structure,fault-tolerant,

Drawbacks:low Power Factor,mechanical limit at very high speed.


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The PMassistance


Conclusions


Synchronous IPM and PM–assisted REL motor:Advantages:

a Power Factor improvement,good Flux–Weakening capability,

Drawbacks:limited overload,high torque ripple.


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The PMassistance


Conclusions


Thank youfor your attention

Department of IndustrialEngineering

University of Padova — Italy


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The PMassistance


Conclusions


N. Bianchi.Electrical Machine Analysis using Finite Elements.Power Electronics and Applications Series. CRC Press, Taylor & Francis Group, Boca Raton, FL, USA,2005.

N. Bianchi. Analysis of the IPM motor – Part I, Analytical approach, in ”Design, Analysis, and Controlof Interior PM Synchronous Machines“ (N. Bianchi, T.M. Jahns editors),IEEE IAS Tutorial Course notes, IAS Annual Meeting, CLEUP, Seattle, October 3, 2005, chapter 3,pages 3.1–3.33 ([email protected]).

N. Bianchi, M. Dai Pré, and S.Bolognani."Design of a fault–tolerant ipm motor for electric power steering."Proc. of IEEE Power Electronics Specialist Conference, PESC’05, 12–16 June 2005.

N. Bianchi, S. Bolognani, Ji-Hoon Jang, and Seung-Ki Sul.“Comparison of PM motor structures and sensorless control techniques for zero-speed rotor positiondetection.”IEEE Trans. on PE, vol.22, no.6, pp. 2466 –2475, Nov. 2007.

N. Bianchi and S. Bolognani."Reducing torque ripple in pm synchronous motors by pole shifting."Proceedings of International Conference on Electrical Machines, ICEM, Aug. Helsinki, 2000.

N. Bianchi, S. Bolognani, D. Bon, and M. Dai Pré,"Rotor flux-barrier design for torque ripple reduction in synchronous reluctance and pm-assistedsynchronous reluctance motors,"IEEE Transactions on Industry Applications, vol. 45, no. 3, pp. 921 –928, May-June 2009.

M. Barcaro and N. Bianchi.“Interior PM Machines using Ferrite to Substitute RareâEarth Surface PM Machines.”Conf. Rec. of Int. Conf. of Electr. Machines, ICEM, Marsille (F), pp. 1–7, June 2012.


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The PMassistance


Conclusions


N. Bianchi, M. Dai Prè, G. Grezzani, and S.Bolognani,“Design Considerations on Fractional–Slot Fault–Tolerant Synchronous Motors,”IEEE Trans. on Industry Applications, vol. 42, no. 4, pp. 997–1006, 2006.

M. Barcaro, N. Bianchi, and F. Magnussen,“Analysis and Tests of a Dual Three-Phase 12-Slot 10-Pole Permanent-Magnet Motor,”IEEE Transactions on Industry Applications, vol. 46, no. 6, pp. 2355–2362, Nov./Dec. 2010.

M. Barcaro and N. Bianchi,“Torque Ripple Reduction in Fractional-Slot Interior PM Machines Optimizing the Flux-BarrierGeometries,”International Conference on Electrical Machines (ICEM), 2012, Sept. 2012.

L. Alberti, M. Barcaro, and N. Bianchi“Design of a Low Torque Ripple Fractional-slot Interior Permanent Magnet Motor.”Conf. Rec. of the 2012 IEEE Energy Conversion Conference and Exposition, ECCE, Raleigh NC, USA,vol. 1, pp. 1–8, 2012.

L. Alberti and N. Bianchi,“Theory and design of fractional-slot multilayer windings,”Energy Conversion Congress and Exposition (ECCE), 2011 IEEE, Sept. 2011, pp. 3112 –3119.


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