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Kufa Journal of Engineering
Vol. 6, No. 2, June, P.P.24-38
Received 3 June 2014, accepted 28 December 2014
DESIGN OF OPEN SOURCE STRAIGHT PERMANENT
MAGNET MOTOR
Dr. Amel A. Ridha1 and Haider H. Jabber2
1 Electronics & Communication Eng. Dep. kufa University /Faculty of Engineering,
amala.alsudani@uokufa.edu.iq
2 Mid. Euphrates Branch, The general company of Electricity Prod. haider-
81@live.com
ABSTRACT
This paper deals with the attraction and repulsion properties of the magnetic field of
permanent magnets in order to produce reciprocating motion in a member of magnetizing
material.
The essential idea of this work have started by putting a string of eight magnets type (Nd Fe
35) spaced by equal spaces placed on the axis between two series of same magnet type each
string consists of nine magnets pieces spaced apart vacuum. Series of internal and external
were organized with different opposite polarity north and south that created a series of free
movement of internal series between the two external strings.
First of all, designed magnetic motor rectal movement consisting of two fixed (for external
strings) and one moving part (Series Interior) analysis was done and its operation was
analyzed. In addition, equations that describe the magnetic field arising from the moving part
were modified by using two-dimensional computer model. The (femm) program was used for
modeling the distribution of density, and DS Solid Works program to study and calculate the
magnetic flux density, field strength and torque generated.
KEYWORDS
Attraction, Flux Density, Free Open Source, Permanent Magnet Motor and Repulsion
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
ND FE 35
FEMMDS SOLIDWORKS
Amel A. Ridha and Haider H. Jabber
1. INTRODUCTION
Today when energy is so expensive, it is not hard to drum up interest for most any avenue
that offers a breath of hope or way of escape. Magnets have enormous importance in the
modern world. It would be hard to imagine life without their contributions in today’s
products. Automobiles have several hundred magnets from motor to sensor applications.
Consumer electronics utilize them to generate video, sound and record; Computers wouldn't
exist; and many high (RPM) instruments used in surgery and dentistry. The main purpose of
magnets is to help in the conversion of energy: Mechanical to Electrical, such as in
generators, sensors and microphones Electrical to Mechanical, such as in motors, actuators
and loudspeakers Mechanical to Mechanical, such as for couplings, bearing and holding
devices [1].
What exactly is a permanent magnet ? what length time does the current need to be in the
coil to make the magnet ? how long can the resulting magnet support its own weight against
gravity? How long human can support his own body weight against gravity before he get
tired ?if someone can't do it ,how come the magnet can? These questions made the inventors
interested with free permanent magnet motor since more than forty years ago.some of them
made the first step of this field and others had shared with this work. some of the inventors
are:
I- Charles J. Flynn, 1995 His work relates to a method of producing useful energy with
magnets as the driving force and represents an important improvrment over known
constructions and it is one which is simpler to construct.can to be self starting. Is easier to
adjust,and is less likely to get out of adjustment, the present construction is also relatively
easy to control, is relatively stable and produces an amazing amount of output energy
considering the source of driving energy that is used. The present construction makes use
permanent magnets as the source of driving energy but shows a novel means of controlling
the magnetic interaction or coupling between the magnet members and in manner which is
relatively rugged,produces a substantial amount of output energy and torque, and in a device
capable of being used to generate substantial a mounts of energy [2].
II- ShenHe Wang,1997. He has designed and built an electrical generator of five kilowatt
capacity. this generator is powered by permanent magnets and so uses no fuel to run.it uses
magnetic particles suspended in a liquid. The motor consists of a rotor which has four arms
and which sits in a shallow of liquid which has a colloidal suspension of magnetic particles in
it. Outer fixed Cylinder has eight N pole Magnets. Inner rotating Cylinder has Six poles
Magnets. Magnetic Shielding is used to create N pole only. By adjusting the alignment of the
N pole magnet ,slight rotation of the Inner cylinder will allow the magnetic repulsion to keep
accelerating the inner cylinder –energy can then be extracted [3].
III- Harold E. Ewilgg, Chandler: Russell R. Chapman; David R. Porten both of
Mesa, all of Ariz, 1997. A simple electrical generator powered by parmanent magents
alone.this generator can also be used as a motor. The construction is not particularly
complicated.it uses an arrangement where permanent magnets. Are associated with every
second coil set around the rotor.operation is self-powered and the magnet arrangment is
clearly defined.and the physical arrangment of the device is not particularly complicated [4].
IV- George Soukup, 2009 His a magnet motor has built on the "V" style of magnet
placement which has two sets of permanent magnets.this style of magnet arrangment has a
locking point where the swicth from wide spacing to narrow spacing occurs and this causes
the rotation to stop there.the taper is much less pronunced with an inner gap some four times
greater than the gap to the outer ring. it also appears that the last inner magnet has a greater
gap around the drum than the remaining ring of magnets. The housing has considrable
clearnce for the drum and magnets. The rear shaft bearing is just set into the back of the
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
housing.the positioning stator magnets allows the motor to overcome the normal sticking
point of the typical V –motor arrangement [5].
V- Dietmar Hohl, 2010.He uses 20 mm diameter round neodymium magnets 10 mm thick,
stacked in pairs in the stator. amagnetic gate arrangement built on a flat piece of Medium-
Density fibreboard 30 mm thick. The holes drilled in it are 20.1 mm in diameter and
positioned so as to take two of the 10 mm thick magnets stacked together.the holes are drilled
at an angle of 63° to the horizontal or 27° to the verti cal.on one side of the board, the inserted
magnets have their North poles facing upwarards,while on the other side of the board,the
magnets are inserted with their south poles facing upwards.his design using angles magnet
pairs ,the number of magnets needed is quite high.for single V ,There are 58 magnets. for a
2-V version,116 magnets.the motor power is liklely to increase as the diameter increases as
the lever arm that the magnet has to turn drum,increases – double the diameter to double the
power [6].
1.1. Permanent Magnet
Two basic types of magnetic materials are soft magnetic materials and hard magnetic
materials. Hard magnetic materials are referred to as permanent magnets because once
magnetized they tend to remain magnetized. Permanent magnets are used as field source
components in a wide range of products including consumer electronic equipment, computers,
data storage devices, electromechanical devices, telecommunications equipment and
biomedical apparatus [7].
The resource crisis of rare earth materials has broken out in motor industry in the world. The
resource of rare earth material is uneven distributed in the globe. The price of these materials
is raising high and high strategically. Nowadays, many of electric motors use rare earth
permanent magnet for the source of magnetic field [8].
In order to configure the magnetic circuit, an operating point has to be set that will determine
the energy transferred from the magnet to the gap. Consider an idealized magnetic circuit
where the magnetic permeability's μr of the soft magnetic materials are infinite so that their
reluctances can be ignored. Since the sum of MMF's in the circuit equals zero, the line
integral of the magnetic field along the path of the circuit
becomes [9]:
Hm Lm = - Hg Lg (1)
Where : Hm is the magnetic field of the magnet in ,
- Lm is the length of the magnet in m,
- Hg is the magnetic field of the gap, in ,
- Lg is the length of the gap in m.
Also, as stated by Maxwell's equation V_B = 0, flux is continuous as it does not have a source
or sink, therefore the total flux in the magnet can be equated to the flux in external space:
Bm Am = Bg Ag (2)
Since in the air gap
Bg = μo Hg (3)
Then (2) becomes
Hm Bm Vm
(4)
Amel A. Ridha and Haider H. Jabber
Then Bm/Hm =
(5)
The quantity Pg = Ag / lg is termed the permanence of the air gap.
As seen in the previous derivation, the ratio Bm / Hm is only dependent on the geometry of the
magnetic circuit.
Fig. 1 illustrates the second quadrant of a permanent magnet's BH curve.
Directly identifiable are the aforementioned quantities Br and Hc. However, once the geometry
of the magnetic circuit has been established and the reluctances calculated, a load line needs
to be drawn, to identify the operating point of the device. The load line typically intersects the
BH curve and has a slope Bd=Hd, as previously mentioned.
As seen from the equation, the slope of the load line is only dependent on the geometry of the
magnetic circuit. However, since the air gap in linear motors and actuators is of variable
dimensions, the load line will also vary, unlike with other magnetic circuits, such as that of a
loudspeaker. Bearing that in mind, the engineer needs to design the circuit in such a way that
the load line is steep enough, so that the magnet is not prone to demagnetization effects; in
the latter case, the operating point of the circuit is not close enough to Hc as needed for a large
sinusoidal signal to demagnetize the magnet.
At the same time, to make good use of the magnet's capabilities, the operating point has to be
close to the point where BH = (BH)max, in order to extract maximum energy from it.
Fig. 1. The load line in (a) is intersecting the demagnetization curve at BHmax. The load line in
(b) is essentially an open circuit, where Bm/Hm → 0 and lg approaches infinity. The load line at
(c) is essentially a short circuit, where Bm/Hm → - ∞ and lg approaches zero.
In a practical situation, however, it is safe practice to account for the magnetic flux leakages
and the finite magnetic permeability. Two new quantities are introduced, namely the leakage
coefficient K1 and the loss factor K2 [10]:-
K1 =
=
(6)
K2 =
(7)
2. OPEN SOURCE DESIGN
Before advancing into practical aspects of this design, the underlying theory has to be
addressed first. In this section, the mathematics underlying will be derived in the design of the
open source motor.
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
2.1. Mathematical Description of the open source
Suppose a bar sample is magnetized by a field applied from left to right and subsequently
removed. Then a north pole is formed at the right end, and a south pole at the left, as shown in
Fig. 2-a, the H lines, radiating out from the north pole and ending at the south pole, constitute
a field both outside and inside the magnet which acts from north to south and which therefore
tends to demagnetize the magnet. This self-demagnetizing action of a magnetized body is
important, not only because of its bearing.
Fig. 2. (a) closed magnetic circuit (b) an open magnetic circuit
The demagnetizing field Hd acts in the opposite direction to the magnetization M which
creates it. In Fig.(2-a) Hd is the only field acting, and the relation B = μₒH . The flux density
B inside the magnet is therefore less than (μₒ M) but in the same direction, because Hd (μₒH
d) can never exceed (μₒ M) in magnitude. These vectors are indicated in Fig. 2, along with a
sketch of the B field of the magnet. Note that lines of B -are continuous and are directed from
south to north inside the magnet. Outside the magnet, B = μₒH and the external fields in Fig.
2-a & 2-b are therefore identical. The magnet of Fig. 2-b is in an open magnetic circuit,
because part of the flux is in the magnet and part is in air [11].
3. PRACTICAL ASPECTS OF THE MOTOR DESIGN
3.1. The idea of Open Source Permanent Magnet Motor
Initially, the idea was to permanently mount the magnets on a straight parallel shaped base.
However, it then became apparent that there is a necessity of making the protype as flexible as
possible.
First In this work we have used parallelogram magnets with arrangement by putting twelve
magnets in two rows with length with different polarity to create a magnetic track by
sending pieces of magnets sliding with length of (20cm) moves between the two rows of
straight magnets. The magnets had got very satisfactory movement. Fig 3-a and 3-b
illustrating: (The idea of straight open source permanent magnet motor) with top views of
the protype which consists of : twelve ceramic magnets placed on two wooden axis with
Amel A. Ridha and Haider H. Jabber
different polarity and sending straight magnets sliding between them). Fig 3-c shows
Isometric of the permanent magnet.
Fig. 3. (a) the top views of the protype , (b) top views of the outer strings and (c) Isometric of
the permanent magnet.
Secondly, it was began by taking each two parallelogram magnets in two rows and arranged
by changing the distance between them and sending a slide of two parallelogram magnets
between them. Notice the North and the South Poles are reversed on the magnets, then
observe the magnetic flux lines between them with (Vizimag) package, as illustrating in Fig.
4.
a b
c
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
Fig. 4. The flux lines distribution of straight open source
Notice the lines between them begin from and go back into the same magnet. These are the
lines of magnetic repulsion.when moving the a slide of magnets through the fixed magnets,
so that the north and south poles face each other, the lines which pass from bottom of one
magnet to the bottom of the other are the lines of magnetic attraction.
Then stack up sixteen magnets on one side and twelve magnets on other sides of stationary
part with (30 cm) length, the distance between the sixteen magnets on the right side less than
the distance between the twelve magnets on the left side(that means there is an angle between
the edge of any magnet on the right side and the another one on the left side, then passing a
slide of six magnets with (15cm) length between them. There are flux lines passing from the
top magnet to the bottom magnet on each side. Fig. 5 illustrate The equivalent magnetic
circuit of straight open source.
Fig. 5. Illustrate The equivalent magnetic circuit of straight open source.
This will not happen when we arrange the magnets in a circle, the circle does not have a first
and last magnet. If we look closely at the middle magnet, we can see what will happen inside
the circle. If the magnets on the right and the left are stationary and the magnets on the
middle are allowed to rotate, the magnets on the right will begin to push the magnets on the
middle away. the magnets on the middle will begin to attract to the magnets on the left. then
the magnets on the left will begin to push the magnets on the middle away. the magnets on
the middle will begin to attract to the magnets on the right. Fig. 6 illustrate two layers of
stationary and moving magnets, each magnet on the middle is moving through different
positions.
Amel A. Ridha and Haider H. Jabber
Notice that there was never occur any lines of attraction between the two layers.This is
because the lines of repulsion are always greater than the lines of attraction. The moving of
free magnets will be easy and smooth and fast.
Fig. 6. Illustrate two layers of stationary and rotary magnets
3.2. Geometry
The purpose of the open source motor is to induce a torque on the rotor, via a magnetic field
gradient. In practice, a continuous gradient as implied by the expression dB=dθ, is possible
only with a circle permanent magnet. The flux density seen from the rotor magnets as the
rotor rotates 2π radians would then resemble very closely to the trend of circular ship, in the
case of an Archimedean circular. The aforementioned magnetization pattern, however, is not
cost effective.
Instead, it was decided that the magnetic field gradient could be assumed continuous by
placing permanent magnets of two sizes in a circular stator and rotor arrangement as follow.It
was decided that the magnetic field gradient could be assumed continuous by placing
numerous permanent magnets of small enough size in a straight arrangement as desired in
Fig. 7. However this would inevitably lead to a B versus θ. The only workaround to get a
good approximation to continuous gradient was to increase the number of density of magnets
and therefore reduce the spacing between adjacent magnets ,in order to get a higher spatial
resolution.
Fig. 7. arrangement of permanent magnets
3.3. Permanent Magnet Material Selection
A specific grade of Neodynium Iron Boron (NdFeB Goe) material was used to provide the
magneto motive force of the inner and outer stages, namely N35. Initially, it was considered
wise to employ NdFeBGoe magnets in the outer and inner structure. The wide commercial
availability of NdFeB Goe magnets made it possible to purchase magnets of decent
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
dimensions and BHmax at a relatively low cost. Appendix (A) lists the magnetic properties
specific to that grade (NdFeB Goe) which was made by (OeMag) company in china.Appendix
(B) shows the sample of N35 magnets with two sizes (14*30)mm & (12*30)mm.
The belts of outer and inner parts of a straight base made of steel on which the permanent
magnets can be attached. Also, the core consists of plastic rod which magnets can be placed.
The magnetic properties of the steel were unknown ,therefore measurements had to be carried
out. The material was available in two sizes namely outer (stator) and inner (rotor).
The magnetic measurements for the magnetic materials were carried out using a permeameter.
The purpose of a magnetic measurements is to extract the magnetic properties of a material,
such as coercively Hc, remanence Br, point of saturation B, and maximum permeability μr
(max). This information can be extracted the B-H loop of the measured material. In addition
to the sample the permeameter involves an induction coil for the measurement of the flux
density B inside the sample. And a Hall prob for measuring H produced by the electromagnet
at the point where B is picked up by the induction coil as shown in Fig. 8 below.
Fig. 8. Schematic of measurement system
The DVM records the voltage across the coil wound around the sample, and feed it to the
PC, which will in turn calculate B. The gaussmeter directly measures H at the point where B
is measured. A digital to analog (D to A) converter is used to connect the PC to the power
supply. A General Purpose Interface Bus (GPIB) is used to connect the gaussmeter and DVM
to the PC. Fig. 9 shows the pareameter for induction coil and the magnet. Appendix (C)
illustrate the experimental setup.
Amel A. Ridha and Haider H. Jabber
Fig. 9. The parameter for induction coil and the sample(14*30)mm
The modeling of the flux lines for the suggest design which used ( Vizimag ) package can
be represented by the Fig. 10-a represents the movement of free magnets on the straight
slides with number of magnets steps when open source was a straight and Fig. 10-b
represents the steps of free magnets on the free rotor with number of magnets steps when
open source was a ring (cycle) shape.
Fig. 10. The movement of free magnets. (a ) when open source was a straight and
(b) when open source was a ring(circular) shape.
(a) ( b)
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
3.4 Straight Permanent Magnet Motor Simulation
At first, the initial mesh was designed in (DS Solidworks package) consistent with the
straight parameters chosen previously as shown in Fig. 11.
Fig. 11. Straight permanent magnet motor initial mesh
The mesh with 23705 nodes was then imported into (Infolytica Magnet) and a static 2D
simulation was performed on both outer (stator) and inner(rotor) the distribution of flux lines
is sketching with (femm), so that the magnetic field gradient can be computed. Fig. 12 shows
the simulation of straight permanent magnet.
Fig. 12. Straight permanent magnet motor simulation result
The steps of inner (rotor) movement inside two outer(stator) are illustrated in Appendix (D).
One of these results is the distribution of flux density as shown in Fig. 13.
Amel A. Ridha and Haider H. Jabber
Fig. 13. The distribution of flux density
4. CONCLUSION
The magnet of (N35) is made with low cost therefore the energy is between 263 -287 that
mean it easy to broken ,so the magnets must be fixed on core with glue to prevent its
damaged.
The core of stator and rotor are made from non-magnetizing and insulator material to reduce
remanance of magnetism or generating the eddy currents.
The sixteen outer magnets are placed with skewing angle =15° between the two magnet's
ends, that mean different poles. This angle was chosen to prevent the loss attraction which
represented by negative sign. while the eight inner magnets are placed with skewing angle
(θ=30°) between each two ends or different poles. This angle was chosen to prevent the
loss attraction which represented by negative sign,that means the angles less them will reduce
the force to zero and the rotor tends to return to its previous position where it will experience
equilibrium. Therefore, at the end the result of simulation was positive for all reading from 1-
19.This angle depends on the result of simulation that shown in Figs. 11 and 12. in addition
to the position angle the direction of inner magnets is opposite to the outer magnets direction.
In this work, a Straight Permanent Magnetic Motor was designed and its operation was
analyzed. Equations described the magnetic field gradient seen by the inner part (rotor)
were developed.
Parallelogram shape had been replaced with Cylindrical shape of magnets because the affect
of edge of parallelogram was appeared on the movement of free magnets, this conclusion
explained at Dietmar Hohl, 2010 because the result torque of his motor had changed from
negative to positive then return to renegative values.his problem was the flux density of the
edges.
A two dimensional computer model of the motor was designed in order to perform a
magnetic analysis.
The magnets (N35) were examined practically with pereameter to calculate the B-H values
and with (DS Solidworks ) package to calculate the torque and speed.
5. FUTURE WORK
After completing the computer simulations to determine the torque and speed, a control
system can be set up. The reason for that is to be controlled the starting and braking of the
Straight Permanent Magnetic Motor and speed controlling at all time.
Kufa Journal of Engineering, Vol. 6, No. 2, 2015
REFERENCES
1- M.Morimoto, “Rare Earth less Traction Motor for Electric Vehicle”, EVS24, The 24th
International Battery, "Hybrid and Fuel Cell Electric Vehicle ", Symposium & Exhibition,
2009.
2- Fulrani P. "Permanent Magnet and Electromechanical Devices". Academic Press,2001.
3- Jacek F. Gieeras,"Permanent Magnet Motor Technology Design and Applications,
Second Edition, Marcel Dekker, 2009.
4- Griffiths D.J. Introduction to Electrodynamics, 3rd Edition. Prentice Hall of India Private
Limited, 2002.
5- Svoboda J. Magnetic Techniques for the Treatment of Materials. Kluwer Academic
Publishers, 2004.
6- B. D. CULLITY & C. D. GRAHAM , " Introduction to magnetic materials ", Second
edition , Wiley publishers, 2009.
7- Charles J. Flynn,United State Patnet, 5,455,474,"Magnetic Motor Construction", 3,
October, 1995.
8- Wang Shum Ho, China Patnet, 97119789. X , "5Kw Electricity Generator", 15 November,
1997.
9- Harold E, Ewing, Chandler; Russell R ,Chapman; David R, Porter, United State Patent,
5,625,241,"Carousel Electric Generator " ,29 April ,1997
10- http://www.patents.com/germany.html
11- Dietmar Hohl, Linz,Patnet Austriak,"Open Source Permanent Magnet Motor", Jan. 2010
APPENDIX (A) :TABLE (1) (NDFEB GOE) MATERIAL PROPERTIES
APPENDIX (B) : THE SAMPLES OF N35 MAGNETS WITH TWO SIZES
(14*30)MM & (12*30)MM.
Amel A. Ridha and Haider H. Jabber
APPENDIX ( C ) : THE EXPERIMENTAL SETUP
APPENDIX (D) : SCHEDULE OF THE STEPS OF INNER (ROTOR) MOVEMENT
INSIDE TWO OUTER(STATOR)
steps
Stationary
South
magnets(RS)
Free magnets
(FR)
Stationary
North
magnets(LS)
Air gap
The distance by
angles (degree)
1
→1
1
1
0
0
2
1
1
1
1.3
15
3
1
1
1
2.6
30
4
1
2
2
4
45
5
2
2
2
5.2
60
6
2
2
2
6.5
75
7
2→3
3
3
7.8
90
8
3
3
3
9.1
105
9
3
3
3
10.5
120
10
4
4
4
11.7
135
11
4
4
4
13
150
12
4→5
4
4
14.4
165
13
5
5
5
15.7
180
14
5
5
5
17
195
15
6
5
5
18.3
210
16
6
6
6
19.6
225
17
6→7
6
6
21
240
18
7
6
6
22.2
255
19
7
7
7
23.5
270
20
8
7
7
24.8
285
21
8
7
7
26
300
22
8→9
8
8
27.5
315
23
9
8
8
28.7
330
24
9
8
8
30
345
