As always, in this month´s Mavilor Express you will find the latest information
about our company and we hope that it will be of interest.
Mavilor Team.
axial-FLUX machines
CHINESE EDITION
RUSSIAN EDITION
Brian J.Chalmers
University of Manchester Institute of Science and Technology
Manchester, UK
Introduction
While the majority of rotating
electrical machines have radial flux
in the air gap between stator and
rotor there is a growing interest in
machines which have axial flux in
the air gap between stators and
rotors which are essentially discshaped. In fact, for any radial-flux
or cylindrical electrical machine
there is an axial-flux or disc-type
CONTENTS
equivalent. Probably the main
reason to consider an axial-gap
topology is its suitability for
mechanical system integration.
There are many forms of axial-flux
machines; this review is
concentrated upon types which
have attracted my attention.
MAVILOR MOTORS, S.A.
1. Introduction
2. Axial-Flux machines
by Brian J. Chalmers
3 . A l k i Te c h n i k
TURKISH EDITION
CZECH. REP. EDITION
4. Mavilor Motors Exposition
Infranor NL Exposition
5. Mavilor around the World
INTRODUCTIO
MARCH 2003
are grateful for Prof. Brian J. Chalmers´ collaboration.
Brian Chalmers has worked in electrical machine research for over 40 years,
specialising in eddy-current effects, induction motors, permanent-magnets
and variable-speed drives. He is now an Emeritus Professor of UMIST, UK,
with continuing activities in international conferences and consultancy.
Thank you very much,
INFRANOR GROUP COMPANY
M A V I L O R EXPRESS
Mavilor Motors around the world
We
Poligono Industrial URVASA
C/. Empordà, 11-13
08130 Sta. Perpètua de Mogoda
(Barcelona) - SPAIN
Tel. +34 935 743 690
Fax. +34 935 743 570
E-mail: mavilor @ mavilor.es
http://www.mavilor.es
As always, in this month´s Mavilor Express you will find the latest information
about our company and we hope that it will be of interest.
Mavilor Team.
axial-FLUX machines
CHINESE EDITION
RUSSIAN EDITION
Brian J.Chalmers
University of Manchester Institute of Science and Technology
Manchester, UK
Introduction
While the majority of rotating
electrical machines have radial flux
in the air gap between stator and
rotor there is a growing interest in
machines which have axial flux in
the air gap between stators and
rotors which are essentially discshaped. In fact, for any radial-flux
or cylindrical electrical machine
there is an axial-flux or disc-type
CONTENTS
equivalent. Probably the main
reason to consider an axial-gap
topology is its suitability for
mechanical system integration.
There are many forms of axial-flux
machines; this review is
concentrated upon types which
have attracted my attention.
MAVILOR MOTORS, S.A.
1. Introduction
2. Axial-Flux machines
by Brian J. Chalmers
3 . A l k i Te c h n i k
TURKISH EDITION
CZECH. REP. EDITION
4. Mavilor Motors Exposition
Infranor NL Exposition
5. Mavilor around the World
INTRODUCTIO
MARCH 2003
are grateful for Prof. Brian J. Chalmers´ collaboration.
Brian Chalmers has worked in electrical machine research for over 40 years,
specialising in eddy-current effects, induction motors, permanent-magnets
and variable-speed drives. He is now an Emeritus Professor of UMIST, UK,
with continuing activities in international conferences and consultancy.
Thank you very much,
INFRANOR GROUP COMPANY
M A V I L O R EXPRESS
Mavilor Motors around the world
We
Poligono Industrial URVASA
C/. Empordà, 11-13
08130 Sta. Perpètua de Mogoda
(Barcelona) - SPAIN
Tel. +34 935 743 690
Fax. +34 935 743 570
E-mail: mavilor @ mavilor.es
http://www.mavilor.es
Ironless armature - requiring
greater magnetising mmf
than an armature with iron
core
Solid armature - in which
induced currents circulate
within a solid conducting
material, which may or may
not be ferromagnetic
Slotless armature - having coils
wound around a laminated,
or composite, iron core
Slotted armature - with
conductors located in slots
and requiring less
magnetising mmf than a slotless
armature.
Topologies include:
Single-sided machine
Double-sided machine, with either
one central armature or two
outer armatures
Multiple disc machine
Rushed dc machines with axial
flux
Axial-flux brushed dc motors have
existed for many years. Typically,
their stationary field system
comprises one or two sets of
permanent magnets mounted on
disc-shaped steel endplates, one
set of magnets sometimes being
replaced by a simple mild steel fluxreturn plate. The armature is often
ironless. Windings may be of printed
circuit type, or stamped from copper
sheet, or may be wire-wound [1].
Solid
armature
machines
The earliest example of an axial-flux
machine with solid armature was the
Faraday disc. The rotating copper
disc `armature` required sliding
contacts for current collection and
the space utilisation was very poor.
The family of eddy current machines,
including couplings, brakes and
dynamometers, have solid
`armatures` in which an iron member
carries both flux and induced
currents. A high-performance eddycurrent dynamometer with axial flux
was developed for use in commercial
testing of automotive engine
systems [3]. This is a double-sided
homopolar inductor machine in
which a pulsation of unidirectional
axial flux is produced by rotation of
a central toothed rotor, causing
power to be dissipated as eddycurrent losses in twin outer loss
members of pure iron. Note that
neither the `armature` nor the field
system rotate. The rotor is a simple
toothed member cut from a steel
plate. The symmetrical
arrangement, with a dc
excitation coil and a loss
member on each side,
minimises magnetic asymmetry
and axial forces. Eddy currents
flow in the plane face of each
loss member adjacent to the
airgap and heat is removed
very effectively by water
flowing in circumferential
channels in the faces of the
lossplates remote from the air
gap. Loadings in these
machines are very high. Thus,
peak flux density in the air gap
is about 1.75 T. Electric loading
in the loss members is about
160 A/mm of periphery at the
mean radius. Designed loss
density at rated power is 100
W/sq.cm. which is several
times that occurring in the largest
turbine generators. The specific
power is exceptionally high, at 10
kW/kg. The range of four production
machines had ratings of 70 kW at
12,000 rev/min, 165 kW at 10,000
rev/min, 300 kW at 7,500 rev/min
and 500 kW at 4,500 rev/min. The
500 kW machine required an active
area of about 0.25sq.m. per side,
with a rotor diameter of just 0.61 m.
These dynamometers have been
applied all over the world.
EXPRESS
The possible formats of axial-flux
machines are summarised below. In
general, the armature, which
carries induced emfs and load
currents, may be either
stationary or rotating.
Alternative armature
arrangements include:
Attributes claimed for these motors
include fast response, high
efficiency, good commutation and
high power-to-weight ratio [2].
Istambul Exhibition
INFRANOR
NETHERLANDS
"Aandrijftechniek 2002" in
Utrecht (NL), which was from 14th of October 2002.
MAV I L O R
M A V I L O R EXPRESS
Formats of axial flux machines
Ironless armature - requiring
greater magnetising mmf
than an armature with iron
core
Solid armature - in which
induced currents circulate
within a solid conducting
material, which may or may
not be ferromagnetic
Slotless armature - having coils
wound around a laminated,
or composite, iron core
Slotted armature - with
conductors located in slots
and requiring less
magnetising mmf than a slotless
armature.
Topologies include:
Single-sided machine
Double-sided machine, with either
one central armature or two
outer armatures
Multiple disc machine
Rushed dc machines with axial
flux
Axial-flux brushed dc motors have
existed for many years. Typically,
their stationary field system
comprises one or two sets of
permanent magnets mounted on
disc-shaped steel endplates, one
set of magnets sometimes being
replaced by a simple mild steel fluxreturn plate. The armature is often
ironless. Windings may be of printed
circuit type, or stamped from copper
sheet, or may be wire-wound [1].
Solid
armature
machines
The earliest example of an axial-flux
machine with solid armature was the
Faraday disc. The rotating copper
disc `armature` required sliding
contacts for current collection and
the space utilisation was very poor.
The family of eddy current machines,
including couplings, brakes and
dynamometers, have solid
`armatures` in which an iron member
carries both flux and induced
currents. A high-performance eddycurrent dynamometer with axial flux
was developed for use in commercial
testing of automotive engine
systems [3]. This is a double-sided
homopolar inductor machine in
which a pulsation of unidirectional
axial flux is produced by rotation of
a central toothed rotor, causing
power to be dissipated as eddycurrent losses in twin outer loss
members of pure iron. Note that
neither the `armature` nor the field
system rotate. The rotor is a simple
toothed member cut from a steel
plate. The symmetrical
arrangement, with a dc
excitation coil and a loss
member on each side,
minimises magnetic asymmetry
and axial forces. Eddy currents
flow in the plane face of each
loss member adjacent to the
airgap and heat is removed
very effectively by water
flowing in circumferential
channels in the faces of the
lossplates remote from the air
gap. Loadings in these
machines are very high. Thus,
peak flux density in the air gap
is about 1.75 T. Electric loading
in the loss members is about
160 A/mm of periphery at the
mean radius. Designed loss
density at rated power is 100
W/sq.cm. which is several
times that occurring in the largest
turbine generators. The specific
power is exceptionally high, at 10
kW/kg. The range of four production
machines had ratings of 70 kW at
12,000 rev/min, 165 kW at 10,000
rev/min, 300 kW at 7,500 rev/min
and 500 kW at 4,500 rev/min. The
500 kW machine required an active
area of about 0.25sq.m. per side,
with a rotor diameter of just 0.61 m.
These dynamometers have been
applied all over the world.
EXPRESS
The possible formats of axial-flux
machines are summarised below. In
general, the armature, which
carries induced emfs and load
currents, may be either
stationary or rotating.
Alternative armature
arrangements include:
Attributes claimed for these motors
include fast response, high
efficiency, good commutation and
high power-to-weight ratio [2].
Istambul Exhibition
INFRANOR
NETHERLANDS
"Aandrijftechniek 2002" in
Utrecht (NL), which was from 14th of October 2002.
MAV I L O R
M A V I L O R EXPRESS
Formats of axial flux machines
MAVILOR
EXPRESS
ON THE
WEB
As for conventional brushless dc
motors, the corresponding
arrangements of brushless axialflux machines have stationary
armatures and rotating permanentmagnet field systems. A variety of
topologies have been developed
and may be used as either motors
or generators.
o n l i n e
You can participate in Mavilor Express. If you
have some important news, a new product, or
something else you would like to communicate,
please send us your information and we will publish
it in our News section.
Now you can find Mavilor Express online at
www.mavilor.es
If you would like to read or print out the latest
editions, all issues are now available on the web.
Kyung Hee Trading Co. Ltd. and Mavilor participated
in the Kofa Trade Show in Seoul from 4th March
until 7th March 2003.
Korea Exhibition
Single-sided motors with slotted
stator have been developed for
motor-in-wheel drives for solar
powered vehicles [6]. An extra thrust
bearing was provided to support the
axial force exerted by the magnets.
This successful design had a high
efficiency (c. 94%), as necessary
for this application, and has been
used by many constructors in longdistance solar-powered race
vehicles.
Multiple disc construction is
applicable when it is desired to
produce high output and rotational
forces impose a limit on rotor
diameter. Multiple-disc, high-speed
generators have been developed
for which special attention was
given to mechanical design [7]. The
armatures are ironless and magnet
flux passes axially through the
machine from end to end.
MAVILOR MOTORS IN ISTANBUL
AND SEOUL EXHIBITIONS
Daye Machine and Mavilor participated in the
OTOMASYON Trade Show in Istanbul from 27th
February until 2th March 2003.
Analysis has shown that optimal
To r u s d e s i g n s h a v e m a g n e t
thickness in the range one to two
times the winding thickness. A more
economic solution may be offered
by slotted strip-wound stator cores,
which require smaller magnet
thickness.
The double-sided Torus machine,
with a central stator and twin outer
rotors, was developed at UMIST [4].
A simple toroidal strip-wound steel
stator core carries a slotless toroidal
winding which may have any chosen
number of phases. For dc generator
applications, rectifiers may
conveniently be mounted on the
stator casing. Machines of this type
have been developed for a variety
of applications [5]. Again, the
symmetrical arrangement minimises
mechanical unbalance but special
attention has to be given to control
axial magnetic forces of attraction
during assembly of the machine.
Induction machines with axial flux
As usual for induction motors, air
gap length must be small and
slotting effects must be controlled.
Axial-flux induction motors should
therefore use slotted strip-wound
cores with small slot openings. Slot
skew, usually in the rotor, is also
desirable and achievable. Singlesided construction necessitates
attention to axial forces. Machines
of this type are in production.
References
[1] Campbell,P: ÒPrinciples of a
permanent-magnet axial-field dc
machineÓ, Proc.IEE, 121, December
1974, pp.1489-1494.
[2] Corbett,A, and Mohamad,MT: ÒThe
disc armature dc motor and its
applicationsÓ, IEE Conf. Pub. No.136,
Small Electrical Machines, 1976. pp.5962.
[3] Chalmers,BJ, and Dukes,BJ: ÒHighperformance eddy-current
dynamometersÓ, IEE Proc., 127,
January 1980, pp.20-28.
[ 4 ] S p o o n e r, E , a n d C h a l m e r s , B J :
ÒTORUS- a slotless toroidal-stator
permanent-magnet generatorÓ, IEE
Proc,B,139,January 1992, pp.497-506.
[ 5 ] C h a l m e r s , B J , S p o o n e r, E ,
H o n o r a t i , O , C r e s c i m b i n i , F, a n d
Caricchi,F: ÒCompact permanentmagnet machinesÓ, Electric Machines
and Power Systems, 25,6,1997, pp.635648.
[6] Patterson,D, and Spee,R: ÒThe
design and development of an axial flux
permanent magnet brushless dc motor
for wheel drive in a solar powered
vehicleÓ, IEEE IAS Conf. Rec., Denver,
Vol.1,1994,pp.188-195.
[7] Etmad,S: ÒHigh speed permanent
magnet axial flux generatorÓ, IEE
Seminar on Permanent Magnet
Materials - Fundamentals, Design and
Application, July 2000.
M A V I L O R EXPRESS
M A V I L O R EXPRESS
Brushless machines with axial
flux
MAVILOR
EXPRESS
ON THE
WEB
As for conventional brushless dc
motors, the corresponding
arrangements of brushless axialflux machines have stationary
armatures and rotating permanentmagnet field systems. A variety of
topologies have been developed
and may be used as either motors
or generators.
o n l i n e
You can participate in Mavilor Express. If you
have some important news, a new product, or
something else you would like to communicate,
please send us your information and we will publish
it in our News section.
Now you can find Mavilor Express online at
www.mavilor.es
If you would like to read or print out the latest
editions, all issues are now available on the web.
Kyung Hee Trading Co. Ltd. and Mavilor participated
in the Kofa Trade Show in Seoul from 4th March
until 7th March 2003.
Korea Exhibition
Single-sided motors with slotted
stator have been developed for
motor-in-wheel drives for solar
powered vehicles [6]. An extra thrust
bearing was provided to support the
axial force exerted by the magnets.
This successful design had a high
efficiency (c. 94%), as necessary
for this application, and has been
used by many constructors in longdistance solar-powered race
vehicles.
Multiple disc construction is
applicable when it is desired to
produce high output and rotational
forces impose a limit on rotor
diameter. Multiple-disc, high-speed
generators have been developed
for which special attention was
given to mechanical design [7]. The
armatures are ironless and magnet
flux passes axially through the
machine from end to end.
MAVILOR MOTORS IN ISTANBUL
AND SEOUL EXHIBITIONS
Daye Machine and Mavilor participated in the
OTOMASYON Trade Show in Istanbul from 27th
February until 2th March 2003.
Analysis has shown that optimal
To r u s d e s i g n s h a v e m a g n e t
thickness in the range one to two
times the winding thickness. A more
economic solution may be offered
by slotted strip-wound stator cores,
which require smaller magnet
thickness.
The double-sided Torus machine,
with a central stator and twin outer
rotors, was developed at UMIST [4].
A simple toroidal strip-wound steel
stator core carries a slotless toroidal
winding which may have any chosen
number of phases. For dc generator
applications, rectifiers may
conveniently be mounted on the
stator casing. Machines of this type
have been developed for a variety
of applications [5]. Again, the
symmetrical arrangement minimises
mechanical unbalance but special
attention has to be given to control
axial magnetic forces of attraction
during assembly of the machine.
Induction machines with axial flux
As usual for induction motors, air
gap length must be small and
slotting effects must be controlled.
Axial-flux induction motors should
therefore use slotted strip-wound
cores with small slot openings. Slot
skew, usually in the rotor, is also
desirable and achievable. Singlesided construction necessitates
attention to axial forces. Machines
of this type are in production.
References
[1] Campbell,P: ÒPrinciples of a
permanent-magnet axial-field dc
machineÓ, Proc.IEE, 121, December
1974, pp.1489-1494.
[2] Corbett,A, and Mohamad,MT: ÒThe
disc armature dc motor and its
applicationsÓ, IEE Conf. Pub. No.136,
Small Electrical Machines, 1976. pp.5962.
[3] Chalmers,BJ, and Dukes,BJ: ÒHighperformance eddy-current
dynamometersÓ, IEE Proc., 127,
January 1980, pp.20-28.
[ 4 ] S p o o n e r, E , a n d C h a l m e r s , B J :
ÒTORUS- a slotless toroidal-stator
permanent-magnet generatorÓ, IEE
Proc,B,139,January 1992, pp.497-506.
[ 5 ] C h a l m e r s , B J , S p o o n e r, E ,
H o n o r a t i , O , C r e s c i m b i n i , F, a n d
Caricchi,F: ÒCompact permanentmagnet machinesÓ, Electric Machines
and Power Systems, 25,6,1997, pp.635648.
[6] Patterson,D, and Spee,R: ÒThe
design and development of an axial flux
permanent magnet brushless dc motor
for wheel drive in a solar powered
vehicleÓ, IEEE IAS Conf. Rec., Denver,
Vol.1,1994,pp.188-195.
[7] Etmad,S: ÒHigh speed permanent
magnet axial flux generatorÓ, IEE
Seminar on Permanent Magnet
Materials - Fundamentals, Design and
Application, July 2000.
M A V I L O R EXPRESS
M A V I L O R EXPRESS
Brushless machines with axial
flux
for their range of hand tools.
In addition to its excellent quality and high output, this product
was chosen for its flexibility in adapting the stator configuration
to specific needs and for the outstanding technical support from
Mavilor, which allowed them to find the best solution for their
application.
mounted on the reducer axis.
M A V I L O R EXPRESS
Alkitechnik selected a BL73 and BL74 kit with stator and rotor
ALKI TECHNICK GmbH
EXPRESS
MAV I L O R
Example of an application for Alkitechnik.
Stator coupled to the housing and rotor
for their range of hand tools.
In addition to its excellent quality and high output, this product
was chosen for its flexibility in adapting the stator configuration
to specific needs and for the outstanding technical support from
Mavilor, which allowed them to find the best solution for their
application.
mounted on the reducer axis.
M A V I L O R EXPRESS
Alkitechnik selected a BL73 and BL74 kit with stator and rotor
ALKI TECHNICK GmbH
EXPRESS
MAV I L O R
Example of an application for Alkitechnik.
Stator coupled to the housing and rotor