Claims:WE CLAIM:

1. A hybrid excited inductor alternator (100) to achieve wide flux regulation, comprising:
? A stator (103) with plurality of teeth (104) for coil winding; and
? A rotor (101) with plurality of teeth (102) for plurality of magnetic poles;
Characterized in that permanent magnetic slots (105) are made in said stator teeth (104) for inserting permanent magnets such that a gap is defined between said magnetic slots (105) and an inner diameter of said stator (103) to create said hybrid excited inductor alternator (100) to achieve wide flux regulation.
2. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein said hybrid excited inductor alternator (100) has 12 magnetic poles.
3. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein said stator (103) has six teeth (104).
4. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein said rotor (101) has six teeth (102).
5. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein the gap between said magnetic slots (105) and inner diameter of said stator (103) is of 10mm.
6. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein two permanent magnetic poles are formed in said stator (103) by inserting 3 magnets per pole.
7. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein filed coils (107) are wound around said stator (103) such that it forms 2 magnetic poles.
8. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein the peak air gap magnetic flux density is 0.05T and RMS value of phase output voltage is 26V.
9. The hybrid excited inductor alternator (100) as claimed in claim 1, wherein gap of 10mm is provided on either side of the permanent magnet slot in said stator teeth (104) to allow the permanent magnet flux leakage within said stator (103) under zero excitation.
, Description:FIELD OF THE INVENTION

[001] The present invention is generally related to the electrical machines. More particularly, the invention relates to the hybrid excited inductor alternators comprising of permanent magnets and excitation windings in the stator part.

BACKGROUND OF THE INVENTION

[002] In order to provide magnetic flux for machine operation, alternators are designed by using either permanent magnets or excitation windings, which is fed by a regulated source. Alternators containing excitation windings to produce magnetic flux can be regulated over a wide range but winding losses occurs in the wound field machines which results in decreasing the machine efficiency. In order to improve the efficiency of alternators, permanent magnets can be used for providing magnetic flux instead of excitation windings but permanent magnet alternators cannot be regulated though higher efficiency can be achieved.

[003] The advantages of the excitation control of conventional alternators and the advantages of higher efficiency of permanent magnet alternators can be attained by a hybrid excited alternators comprising both excitation windings and permanent magnets in the rotor core. But the rotor excited hybrid alternators are to be provided with slip rings or alternative arrangement to excite the field winding. Few rotor excitation topologies are discussed in the patents US9356479B2, EP2599196B1, JP5673640B2, DE112013000314T5 and WO2014006294A1.

[004] US9356479B2 discloses a hybrid excitation machine comprising a rotor having first and second rotor cores with a gap between in an axial direction, wherein first magnetic poles excited by a permanent magnet and second magnetic poles not excited by the permanent magnet are alternately arranged in a circumferential direction in each rotor core. The first magnetic poles of the first and second rotor cores have different polarities, and the first magnetic poles of one rotor, core face the second magnetic poles of the other rotor core in the axial direction. A stator generating a magnetic field rotating the motor is placed radially outward of the rotor and an exciting coil exciting the second magnetic poles is placed in the gap, wherein the stator has, in the axial direction, first stator cores on both sides and a second stator core having lower magnetic resistance than the first stator core, in a center.

[005] EP2599196B1 discloses a synchronous rotary electric machine comprising a rotor provided with permanent magnets and an excitation winding. More particularly, the invention relates to a machine of this type for applications such as generator and / or electric traction motor in electric and hybrid vehicles. It provides a synchronous rotating electrical machine with double excitation type rotor topology that disclosed in the above article and whose design has been optimized to increase performance and interest of these machines automobile industry.

[006] JP5673640B2 discloses a hybrid excitation type rotating electrical machine, in particular, it relates to a hybrid excitation type rotating electrical machine using both the permanent magnet and an electromagnet as the exciting circuit. According to JP567364B2, by disposing the excitation coil for exciting the permanent magnet de-energized pole in position it can be realized without increasing the size of the desired magnetic circuit forming.

[007] The machine according to WO2014006294A1 is of the type of those comprising a rotor (2) having alternating north and south poles and excitation coils (3) housed in first recesses (4) which are distributed regularly around a shaft (5) of the rotor. These first recesses are arranged radially in the rotor between a central part and a circumferential part of the rotor and extend axially, in such a way as to define polar sections (6). Each excitation coil is inserted around a core forming a partition between two first consecutive recesses, the core being substantially aligned with a central radial axis (d) of the corresponding polar section. In accordance with the invention, the rotor furthermore comprises a plurality of permanent magnets (7) exhibiting a substantially tangential direction of magnetization, which are arranged in second recesses (8) and extend substantially in radial symmetry planes of the polar sections (6), in such a way as to compensate the armature magnetic feedback.

[008] Few inductor alternator topologies are discussed in the patents US6075302A, EP17778008A2, EP1208636B1 and US6323573B1. Hence in order to achieve the wide flux regulation without the need of slip rings, hybrid excited alternator with stator comprising of field winding, permanent magnets and armature winding is proposed in the present invention.

[009] US6075302A discloses a multiple phase heteropolar inductor electrical machine utilizing relatively movable stators and rotors wherein the rotors include electrical winding for producing electricity. The stators and rotors are spaced as to produce an electrical balancing among the machine phases. Preferably, a balance is achieved in the energy conversion process as measured over any given one-half electrical cycle within that phase. The machine substantially achieves equal and balanced peak torque per amp performance within a half cycle of operation of any given phase through the spacing between the stator and elements.

[0010] EP1208636B1 discloses an electrical machine comprises a rotor without windings, a stator having an armature winding (24, 25) and a field winding (10) for generating a magnetomotive force in a direction extending transversely of the magnetomotive force generated by the armature winding. An electronic circuit (40) is provided for controlling the current in the armature winding (24, 25) such that periods in which a magnetomotive force in one direction is associated with a first current pulse alternate with periods in which a magnetomotive force in the opposite direction is associated with a second current pulse. A position sensor is provided for monitoring the rotational position of the rotor and for supplying output signals dependent on the speed of rotation of the rotor. Furthermore a control system (32) supplies control signals to the circuit (40) to control the current in the armature winding (24, 25). In order to enhance the performance at high speed, the control signals are produced in response to sensor output signals which provide an advanced indication of the rotational position of the rotor. Furthermore, in order to prevent oscillation of the rotor on start-up, the control signals supplied to the circuit (40) during an initial start-up period are each produced after a time delay as compared with the production of the control signals over subsequent cycles of rotation during acceleration of the rotor. This can be achieved with simple on/off control of armature and field switching devices, so that the control circuitry can be produced at relatively low cost.

[0011] According to the present invention, the foregoing and other disadvantages, shortcomings, inefficiencies and problems are overcome by providing a hybrid excited inductor alternator to achieve wide flux regulation.
OBJECTS OF THE INVENTION
[0012] The principal object of the present disclosure is to provide a hybrid excited alternator to achieve wide voltage regulation without the need for slip rings.

[0013] Another object of the present invention is to provide a hybrid excited alternator that works on the principle of inductor alternator.

[0014] Yet, another object of the invention is to provide the stator configuration for accommodating both excitation windings and permanent magnets along with armature winding.

SUMMARY OF THE INVENTION
[0015] According to the aspect of the invention, a hybrid excited inductor alternators comprising of permanent magnets and excitation windings in the stator part is disclosed for achieving wide regulation in the output voltage.

[0016] The stator of the hybrid excited inductor alternator is significant in that the permanent magnet slots are provided well inside the stator teeth unlike in the conventional permanent magnet inductor alternator stator where the permanent magnet slots are provided just above the stator inner diameter. The purpose of this arrangement is to allow the magnetic flux leakage within the stator teeth. The space on either end of the permanent magnet slots will also be provided in the stator teeth to aid the magnetic flux leakage within the stator teeth under zero excitation.

[0017] The stator of the hybrid excited inductor alternator is also significant in that it has two stator slots for excitation winding and the remaining stator slots for armature windings. In case the excitation winding MMF requirement is less, the small armature coil can also be placed along with the field winding. The permanent magnets and field winding are placed in the stator such that it forms two magnetic poles.

BRIEF DESCRIPTION OF DRAWNGS
The proposed invention will be better understood by the following description with reference to the accompanying drawings:

[0018] Figure 1 is a sectional view of the hybrid excited inductor alternator with stator comprising of permanent magnets, filed and armature windings.

[0019] Figure 2 is the flux vector plot of the hybrid excited inductor alternator when field windings are not excited.

[0020] Figure 3 is the air gap flux density plot of the hybrid excited inductor alternator when field windings are not excited.

[0021] Figure 4 is output voltage of the hybrid excited inductor alternator when field windings are not excited.

[0022] Figure 5 is the flux line plot of the hybrid excited inductor alternator when field windings are excited with rated MMF.

[0023] Figure 6 is the air gap flux density plot of the hybrid excited inductor alternator when field windings are excited with rated MMF.

[0024] Figure 7 is output voltage of the hybrid excited inductor alternator when field windings are excited with rated MMF.

DETAIL DESCRIPTION OF THE INVENTION

[0025] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.
[0026] In the present disclosure, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
[0027] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the present disclosure to the particular forms disclosed, but on the contrary, the present disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the present disclosure.
[0028] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
[0029] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0030] The present invention will be described in detail below with reference to an embodiment as shown in the drawing.
[0031] A 12-pole hybrid excited inductor alternator is designed in the present invention with stator and rotor configurations as shown in Fig. 1. In order to have 12 poles the rotor 101 in the inductor alternator should have six teeth 102. The stator 103 also has six teeth 104 around which the coils will be wound. In the present invention, the permanent magnet slots 105 are made in the stator teeth. Usually the permanent magnet slots are made in the stator teeth just above the stator inner diameter in order to have high air gap magnetic flux density. But in the present invention, approximately 10 mm portion is left between permanent magnet slot and stator inner diameter. In addition to this, approximately 10 mm portion is also left on either end of the permanent magnet slot in the stator teeth. This kind of providing space around the permanent magnet slot is not desirable in the case of permanent magnet inductor alternator. The iron part around the permanent magnet slot allows the leakage of magnetic flux within the stator tooth thereby reducing the air gap flux linking the rotor.

[0032] Two permanent magnet poles will be formed in the stator by inserting three magnets per pole. The armature coils 106 and filed coils 107 are placed in the stator slots as shown in Fig. 1. The filed coil is to be wound such that it forms two magnetic poles and armature coils are to be connected in series. Two opposite stator slots are chosen for placing field coil. If the field coil MMF requirement is less then small armature coils can also be arranged along with the field coils. The permanent magnets are to be pasted into the permanent magnet slots before the placement of coils into the stator slots.

[0033] Two permanent magnet poles will be formed in the stator by inserting three magnets per pole. The armature coils 106 and filed coils 107 are placed in the stator slots as shown in Fig. 1. The filed coil is to be wound such that it forms two magnetic poles and armature coils are to be connected in series. Two opposite stator slots are chosen for placing field coil. If the field coil MMF requirement is less then small armature coils can also be arranged along with the field coils. The permanent magnets are to be pasted into the permanent magnet slots before the placement of coils into the stator slots.

[0034] When the field windings are not excited, most of the magnetic flux will leak within the stator teeth and only some of the magnetic flux will link the rotor part. When the field windings are positively excited (electromagnetic flux and permanent magnet flux are in same direction), the leakage flux within the stator teeth reduces and the air gap flux will increase to the maximum value. Similarly when the field windings are negatively excited (electromagnetic flux and permanent magnet flux are in opposite direction), the leakage flux within the stator teeth increases to the maximum value and the air gap flux will become almost zero. Thus in the present invention, an approach proposed for accommodating excitation windings, permanent magnets and armature windings in the stator of a hybrid excited inductor alternator achieves wide regulation in the magnetic flux density.

[0035] The transient analysis using FEM software has been carried out on the proposed hybrid excited inductor alternator without exciting the field windings to determine and plot the flow of flux lines (as shown in Fig. 2), the air gap magnetic flux density (as shown in Fig. 3) and the output voltage waveform (as shown in Fig. 4). The peak air gap magnetic flux density is 0.05 T. The RMS value of phase output voltage is 26 V. The transient analysis using FEM software has also been carried out on the proposed hybrid excited inductor alternator with field windings excited at rated excitation to determine and plot the flow of flux lines (as shown in Fig. 5), the air gap magnetic flux density (as shown in Fig. 6) and the output voltage waveform (as shown in Fig. 7). The peak air gap magnetic flux density is 0.62 T. The RMS value of phase output voltage is 594 V.

[0036] The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the specification, the reference numerals are merely for convenience, and are not to be in any way limiting, the invention may be practiced otherwise than is specifically described.