FIELD OF INVENTION:
This invention relates to an alternator. In particular, this invention relates to an alternator operable at low rotational speeds, and adapted to produce high voltage and current.
INTRODUCTION:
Generation of electric power and consumption is part of the modern way of living. Various sources of energy have been used to produce electric power. Large scale power plants consume hydro, thermal, fusil coal and nuclear energy, to generate electricity.
The first electric current generator were known as dynamos and was widely used to generate direct current (DC) power for industry. Typically in a dynamo a stationary structure, called stator provides a constant magnetic field. A set of rotating windings called a rotor, rotates within the stator to produce electric power. A commutator (switch for reversing the direction of an electric current) is mounted on the rotor shaft and carbon brushes in contact with the segmented commutator collects direct current output.
When a loop of wire cuts across in a magnetic field, the potential induced in it reverses as it begins to move out of the magnetic field, generating an alternating current. The commutator is needed to produce direct current. In the early days of electric generation and usage, alternating current had no known applications. On small machines the constant magnetic field may be provided by one or more permanent magnets whereas larger machines were provided with electromagnets, which are known as field excitation coils.

Centralized power generation and distribution became possible when it was recognized that alternating current electric power could be transported at low costs across great distances.
An alternating current generator produces an alternating voltage, which means the polarity of the voltage changes direction repeatedly. The polarity change is called the frequency and is expressed in cycles per second. In a alternator a conductor cuts across magnetic field to induce electromotive force called emf. The emf is measured in volts. Voltage is generated according to Faraday's Law which states that a time varying magnetic field will induce an electric current. Alternating voltage may be generated by rotating a coil in the magnetic field or by rotating a magnetic field within a stationary coil. The voltage generated depends on: the number of turns in the coil; strength of the magnetic field and the speed at which the coil or magnetic field rotates. In a conventional alternator to produce usable form of electric energy the rotor of the alternator needs to rotate at fairly high speeds.
Large permanent magnet alternator were not practical, due to the high cost of the magnetic material and the problem of retention of magnetism over hot operating conditions. Rare-earth magnets like neodymium and samarium-cobalt magnets strong permanent magnets made from alloys of rare earth elements. Rare-earth magnets are the strongest type of permanent magnets, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can be in excess of 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. Rare earth magnets are extremely brittle and also vulnerable to corrosion, so they are usually plated or coated to protect them from breaking and chipping.

The increase in capacity to manufacture of affordable, high-energy permanent magnet especially rare-earth magnets like Neodymium-Iron-Boron (NdFeB) has resulted in development of permanent magnet alternators for various energy conversion applications.
A permanent magnet alternator may be classified based on the orientation of the magnetic flux within the machine,
1) The magnetic field can be given a radial direction by placing the stator around the rotor. A machine construction like this is called a radial flux machine.
2) The magnetic field can be given an axial direction by placing the stator
adjacent to the rotor such that the air gap is perpendicular to the rotational axis and the magnetic flux crosses the air gap in axial direction. A machine construction like this is called a axial flux machine.
Another classification of the alternator is based on the type of construction used to position the permanent magnets. In a surface mounted permanent magnet (SMPM) construction it is required to shape the magnets into arcs, which can be placed on the outer surface of a rotor or the inner surface of a stator. Alternatively in a an inset magnet permanent magnet (IMPM) alternator the magnets are embed into the rotor or stator constructed of magnetic material. The advantage of the inset magnet topology is the possibility to use unshaped magnets.
The advantages of the surface mounted radial flux permanent magnet (SMRFPM) Alternator in accordance with this invention includes lightweight, compact size, simple mechanical construction, easy maintenance, high reliability, higher efficiency, and absence of moving contacts.

PRIORART:
Australian innovation patent 2013 100035 patent describes a "Permanent magnet alternator for low speed applications" consisting of two or more rotor discs in which a plurality of rare earth magnets are configured as polar array around a central shaft with their polarity alternately arranged parallel to the shaft. At least one disc stator secured radially to the frame, consisting of coils wound around inductive ferrite cores, configured in a similar polar array and suspended between the two rotor discs. When the rotor assembly is turned, the stator coils are so arranged as to coaxially align with the rotor magnets, thus interacting with the magnetic flux and generating electrical AC output power.
US Patent 6,137,199describes a "Alternator with permanent magnet rotor having primary magnets and blocking-pole magnets", having a one-piece, rotor hub backslash flywheel backslash starting gear. Three high remanence ceramic permanent magnets provide a rotor having a contiguous ring of twelve alternating poles which allows for higher alternator efficiency. The magnets are ceramic and are adhesively bound to the rotor hub, which is driven by an extended crankshaft. The rotor rotates within a wound stator assembly of which the laminated stator core is a part of the alternator's frame assembly, and thus, serves as a shield should a rotor magnet come loose.
US Patent 6967417 describes a "Variable winding generator" having a high efficiency over wide ranges in rotor speed and power output requirements. Output voltage control is achieved by providing the power output windings with variable adjustment. This variable adjustment determines the number of turns that are used for the power output on the power output windings themselves. When excess

voltage is generated, turns used on the power output windings are reduced thereby reducing output voltage and increasing efficiency by lowering the power output winding resistance. When the voltage generated is low, more turns on the power output windings are activated thereby increasing the voltage of the generator itself. This voltage control occurs prior to any voltage modification outside of the generator. A sensor and feedback mechanism is used to automatically adjust the power output windings thereby attaining maximum efficiency at the desired voltage and power level.
The US Patent 7005772 describes a "Stator winding having two slots per phase per pole " comprising a generally cylindrically-shaped stator core having a plurality of circumferentially-spaced and axially-extending core teeth that define a plurality of circumferentially-spaced and axially-extending core slots extending between first and second ends of the stator core. Within the core is a stator winding having a plurality of phases, each of the phases including a pair of conductors connected in parallel and having a plurality of slot segments housed in the core slots. The slot segments are alternately connected at the first and second ends of the stator core by a plurality of end loop segments. The conductors within each pair of each phase are connected in parallel and are in phase with one another such that the stator core has two slots per phase per pole.
This invention envisages a new alternator system comprising the following components. An external rotor assembly having high-energy Permanent Magnets mounted on the internal cylindrical surface, an internal stator assembly with windings having special layout and terminations.

The permanent magnet (PM) alternator offers high efficiency in operation and a simple and robust structure in construction because field current winding are absent. The performance of PM alternators is further enhanced by the availability of high-energy magnetic materials such as Neodymium-Iron-Boron.
The main features of the invention of Radial Flux Permanent Magnet Alternator in accordance with this invention are as under:
The Radial Flux Permanent Magnet Alternator (RFPMA), in accordance with this invention is of simple mechanical construction. There are no surface contact component that cause wear and tear making the alternator easy to maintain. The alternator in accordance with this invention is a ring type Permanent Magnet Brushless Alternator with an external rotor and an internal stator. The alternator in accordance with this invention is a totally closed design which provides protection to the alternator against contamination due to rain, dust, foreign matter of the coil and magnets by foreign particles.
OBJECTS OF THIS INVENTION:
One of the objects of this invention is to provide a permanent magnet alternator suitable for industrial applications.
Yet another object of this invention is to provide a permanent magnet alternator adapted to produce single phase alternating current at low rotational speeds.

Another object of this invention is to provide a permanent magnet alternator adapted to produce output voltage proportional to the rotary speed within the designed range of the unit.
Still another object of this invention is to provide a permanent magnet alternator having low starting and running torques.
Still another object of this invention is to provide a permanent magnet alternator capable of high output voltage and current and low in put energy to achieve high efficiency.
Yet another object of this invention is to provide a permanent magnet alternator, which does not require slip ring or brushes.
One more object of the present invention is to provide a permanent magnet alternator, which is easy to manufacture.
One more object of the present invention is to provide a permanent magnet alternator, which has inherently low wear and tear due to low speed operation.

One more object of the present invention is to provide a permanent magnet alternator having low noise and vibration.
Yet another object of this invention is to provide a permanent magnet alternator, which does not require external active cooling devices.
Another object of the present invention is to provide a permanent magnet alternator, which is easy to maintain.
Yet another object of the present invention is to provide a permanent magnet alternator, which is robust in construction.
Still one more object of the present invention is to provide a permanent magnet alternator, which is economical in operation.
SUMMARY OF THE INVENTION:
According to this invention there is provided a permanent magnet alternator, comprising: a rotor adapted to receive permanent magnets mounted in a preselected orientation; a stator adapted to receive conductors coils wound in slots provided on said stator; end covers adapted to be fasten said rotor and stator; roller bearing elements positioned so as to permit relative movement between said rotor and stator; in an operative assembled configuration said rotor adapted revolve around said stator to induce electromotive force in said copper conductors, characterised in that, the alignment of orientation of magnetic pole of one

permanent magnet is opposite to the orientation of magnetic poles of the rest of the magnets in the array, the placement of copper conductor in a slot is shared between two adjacent coils; and said conductor coils divided in groups and connected in alternate group formation of 1-3-5-7 8-2-4-6.
Typically the permanent magnets are selected from a group of permanent magnets consisting of Alnico, Samarium-Cobalt, and Neodymium-Iron-Boron magnets.
Typically the permanent magnets are rectangular in cross section.
Typically the permanent magnets are coated with a coating selected from a group consisting of metallic coatings, inorganic coatings.
Typically the permanent magnets are surface mounted on the inner circumferential surface of said rotor.
Typically the copper conductors are enameled copper wires.
Typically conductors placed in a slot are equally distributed in two adjacent coils.

BRIEF DESCRIPTION OF THE DRAWINGS:
All aspects and advantages of the present invention will become apparent with the description of the preferred non limiting embodiment, when read together with the accompanying drawings, in which:
Figure 1 is the elevation of the permanent magnet alternator in accordance with this invention;
Figure 2 is a photographic perspective view of the permanent magnet alternator shown in figure 1 ,in accordance with this invention;
Figure 3 is the end elevation of the external rotor provided with the permanent magnets of the alternator shown in figure 1, in accordance with this invention;
Figure 4 is the sectional view of the external rotor provided with the permanent magnets of the alternator shown in figure 1, in accordance with this invention;
Figure 5 is the plan of the internal stator, without the stator windings of the permanent magnet alternator shown in figure 1 ,in accordance with this invention;
Figure 6 is the elevation of the internal stator, without the stator windings of the permanent magnet alternator shown in figure l,in accordance with this invention;

Figure 7 is the elevation of the external rotor and the internal stator, without the stator windings , in an assembled condition, of the permanent magnet alternator shown in figure l,in accordance with this invention;
Figure 8 is a photographic perspective view of the external rotor, internal stator and windings of the permanent magnet alternator shown in figure l,in accordance with this invention; and
Figure 9 is the schematic layout of stator winding terminations of the permanent magnet alternator shown in figure l,in accordance with this invention.
DETAILED DESCRIPTION OF THE DRAWING:
Referring to the accompanying drawings the radial flux permanent magnet alternator according to this invention is indicated generally by the reference numeral 100.
Referring to figure 1 and figure 2, the radial flux permanent magnet alternator (100) consists of a hollow cylindrical rotor (10). A set of permanent magnets (12) irremovably fixed to the internal cylindrical surface of the rotor (10). A stator (14) having an axial shaft (16) extending on either side of the stator (14). End covers (18) and (20) provided with roller bearing (20) and (22) adapted to position the stator (14) within internal cylindrical space defined by the rotor (10) and provide free rotational movement of the rotor (10) with reference to the stator (14). In an assembled condition of said rotor unit (10), stator unit (14), End covers (18) and

(20) and bearing units (20) and (22) said axial shaft (16) extending outward on either side of the end covers(18) and (20). A drive transmission sprocket wheel element'(24) removably fixed to the end cover (20) using mounting plate element (19). Additional drive transmission belt wheel element (26) provided on the outer cylindrical surface of said rotor(l0).
Referring to figure 3 and figure 4, the radial flux permanent magnet alternator (100) consists of a hollow cylinder rotor (10). The permanent magnets (12) are mounted on the internal cylindrical surface of the rotor (10) in a pre determined sequence. The permanent magnets (12) are fitted substantially parallel to the axis defined by the hollow cylindrical rotor (10). The orientation of the magnetic poles of the permanent magnets is arranged in a manner that the south poles of the magnets point towards one direction other than one magnet which is positioned to have its north pole pointing in that direction. Referring to figure 8 the radial flux permanent magnet alternator (100) was constructed with permanent magnets one to forty having their south pole aligned in one operative direction and the forty first magnet having its north pole aligned in the same direction.
Referring figures 5 and 6 the stator (14) of the radial flux permanent magnet alternator (100) comprises of the axial shaft (16) provided with a disc (30) mounted substantially in the central location along the axis of the shaft (16). The disc (30) provided with radially arrayed cutouts (32) and radial ribs (34) arrayed in between the cutouts (32). A set of stampings (36) having slots (38), electrical conductors (not specifically shown) provided on the outer cylindrical surface of

the disc (30). The electrical conductors (not specifically shown) are separated by insulation material and retain the windings in the slot (38).
Referring to figure 7 and figure 8, in an assembled condition of the rotor (10), the stator (14) and the end covers (18 & 20) the air gap (X) between the rotor (10) and the stator (14) is maintained by the provision of roller bearing (20) and (22).
Referring to figure 9 the inter connection of the electrical conductors wound in the slots (38) of the stampings (36) are shown. Each of the slots provided on the stampings accommodate 50% of adjacently positioned coils. The coils are divided into eight overlapping segments and are inter connected as shown providing two power output wires adapted to be led out of the stator (14) through the central hole provided on the axial shaft (16).
A radial flux permanent magnet alternator in accordance with this invention was designed and built as follows.
The rotor was fabricated by rolling a flat steel sheet to form a cylindrical shell. The cylindrical shell was welded and was stress relieved and machined to the required tolerance. Permanent magnets of Neodymium-Iron-Boron type with rectangular cross section were selected. These magnets were aligned along the central axis of the cylindrical shell were glued to the machined internal cylindrical surface of the rotor using mounting jig plate. Also the north south poles of each magnet was checked and magnets one to forty were positioned with their south pole aligned in one operative direction and the forty first magnet was positioned with its north pole aligned in the same direction.

The stator stampings in the form of discs were blanked in a press machine with slots provided on the outer circumference. These segments were assembled together and fitted on the circular disc provided with cutouts and central ribs. The central shaft was assembled in the centre of the disc. The shaft was pre machined to the required tolerance to form the stator assembly. Insulated copper conductor windings were placed in the slots and fixed in place. The copper windings were terminated as shown in figure 9 and two power output leads were insulated.
Two roller bearing with adequate radial and axial load bearing capacities to withstand potential starting and running stress likely to be encountered in prolonged usages were selected . The stator , rotor, and the roller bearings were assembled by the end covers and drive transmission elements like sprocket wheel and belt pulley were mounted together using suitable fasteners.
The completed assembly of the alternator in accordance with this invention was mounted on a test rig and rotated at speed range of 50 to 500 rpm of the rotor. The test results of various parameters are as follows:

S.NO SPEED (RPM) VOLTAGE(VOLTS) CURRENT(AMPS) FREQUENCY(CPS)
1 50 20 6 17

2 100 50 14 47
3 200 186 23 78
4 300 128 30 125
5 500 200 40 185
6 1000 205 41 188
In a test conducted on an alternator built with similar design, material size, winding terminations, and sharing of slots but with conventional NORTH-SOUTH magnetic pole orientation of permanent magnets the results were as follows:

S.NO SPEED(RPM) VOLTAGE (VOLTS) CURRENT (AMPS)
1 50 10 1
2 100 20 2
3 300 40 3
4 500 60 4
In another test conducted on an alternator built with similar design, material, size but with conventional NORTH-SOUTH magnetic pole orientation of permanent

magnets and conventional winding terminations without the provision of placing winding in shared slots the results were as follows:

S.N0 SPEED(RPM) VOLTAGE(VOLTS) CURRENT(AMPS)
1 < 1000 NIL NIL
2 1000 20 2
A radial flux permanent magnet alternator (100) in accordance with this invention has wide industrial applications including:
Automotive applications:
In a fully battery operated or combination of internal combustion plus battery operated hybrid vehicles the battery used to drive an electric motor to propel the vehicle. Recharging the battery at the end of the rated usage is carried out by connecting the battery to an external electric power source. The range of effective distance covered between recharge varies according to type of vehicle, whether type of drive includes regenerative breaking and such other facts. The usage of radial flux permanent magnet alternator (100) in accordance with this invention will increase the time interval and distance covered between recharge by an estimated 5 to 6 times as compared to conventional configuration. The radial flux permanent magnet alternator (100) is able to produce sufficiently high output of eclectic voltage and current even at low speed having low torque input requirement

due to the innovative arrangement of the magnetic pole positioning and method of windings used in accordance with this invention. In an automotive application the radial flux permanent magnet alternator (100) in accordance with this invention is envisaged to be used in conjunction with a motive power like an internal combustion engine or an electric motor to intermittently absorb rotational power from the motive power drive unit through a clutch mechanism and produce electric power to keep the batteries in a properly charged condition and thereby reduce the frequency of recharging of the batteries, which alone also increases the life cycle of the batteries.
Stationary application:
The radial flux permanent magnet alternator (100) in accordance with this invention is also envisaged to be used as alternate energy source for regular or standby power source by use in conjunction with a wind turbine, battery and inverter to produce electric power by providing rectifier and inverter circuit for keeping the batteries charged and produce eclectic power for domestic, commercial or industrial applications. The radial flux permanent magnet alternator (100) can effectively replace the polluting internal combustion engine used to produce standby electricity in commercial application like shops, mobile towers and industries.
While considerable emphasis has been placed herein on the particular features of "radial flux permanent magnet alternator " and the improvisation with regards to it, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other modifications in the nature of the

invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. A permanent magnet alternator (100) comprising: a rotor (10) adapted to receive permanent magnets (12) mounted in a preselected orientation; a stator (14) adapted to receive conductors coils wound in slots(28) provided on said stator(14), end covers (18 and 20)adapted to be fasten said rotor (10) and stator(14), roller bearing elements (20 and 22) positioned so as to permit relative movement between said rotor (10) and stator (14), in an operative assembled configuration said rotor (10) adapted revolve around said stator (14) to induce electromotive force in said copper conductors, characterised in that: (i) alignment of orientation of magnetic pole of one permanent magnet is
opposite to the orientation of magnetic poles of the rest of the magnets
in the array; (ii) the placement of copper conductor in a slot is shared between two
adjacent coils; and (iii) said conductor coils divided in groups and connected in alternate
group formation of 1-3-5-7-8-2-4-6
2, A permanent magnet alternator as claimed in claim 1, wherein the permanent
. magnets are selected from a group of permanent magnets consisting of Alnico,
Samarium-Cobalt, and Neodymium-Iron-Boron magnets.
3. A permanent magnet alternator as claimed in claim 1, wherein the permanent
magnets are rectangular in cross section.

4. A permanent magnet alternator as claimed in claim 1, wherein the permanent magnets are coated with a coating selected from a group consisting of metallic coatings, inorganic coatings.
5. A permanent magnet alternator as-claimed in claim 1, wherein the permanent magnets are surface mounted on the inner circumferential surface of said rotor.
6. A permanent magnet alternator as claimed in claim 1, wherein the copper conductors are enameled copper wires.
7. A permanent magnet alternator as claimed in claim 1, wherein conductors placed in a slot are equally distributed in two adjacent coils.
8. A permanent magnet alternator as described herein with the accompanying drawings.