FIELD OF INVENTION:
The present invention is generally relates to the electrical machines and in particular to the permanent magnet synchronous generator. More particularly, the invention is relates to the slot profile in the stator core of permanent magnet synchronous generator.
BACKGROUND OF INVENTION:
Though few functional application require the alternators with poor regulation as it limits the value of short-circuit current, most of the functional application require alternators with better voltage regulation. One of the important factors for poor voltage regulation of alternator is the armature reaction that can be observed when the alternator is loaded. The more the armature reaction of the synchronous generator, more will be the percentage voltage regulation of the synchronous generator which is undesirable. The voltage regulation of permanent magnet synchronous generator has to be improved during the generator design itself by choosing appropriate high grade permanent magnets unlike the voltage regulation of conventional synchronous generator which can be improved after the generator design by controlling the excitation level of field windings provided in the rotor core.
In JP09285090A patent application, a complex rotor structure of an electrical machine with utilization of inter-polar permanent magnets in addition to main permanent magnets is proposed in order to reduce the armature reaction. In addition to the complexities involved in the rotor structure, the utilization of inter-polar permanent magnets reduces the space availability for main permanent magnets there by reducing the flux output of main permanent magnets.

OBJECTS OF THE INVENTION:
An object of the invention is to reduce the armature reaction effect in permanent magnet synchronous generator.
Another object is to provide a novel slot profile to be used in the stator core of permanent magnet synchronous generator.
Another object is to provide a partition in the slot profile to create an alternative path for the flux lines of certain amount of stator winding when the permanent magnet synchronous generator is loaded.
SUMMARY OF THE INVENTION:
According to an aspect of the invention, a novel slot profile of stator core of permanent magnet synchronous generator is proposed in order to reduce the armature reaction effect. The novel slot profile to be used in the stator core of permanent magnet synchronous generator for reducing the armature reaction effect is significant in that the slot will have a partition as shown in Fig. 1 so that the winding can be accommodated above the partition and below the partition in the slot.
The novel slot profile proposed in the present invention is also significant in that the partition provided in the slot having opening through which the copper conductors can be inserted in order to place the winding above the partition in the slot.
The novel slot profile is also significant in that the partition provided in it is made of stator core material and hence the flux lines due to current carrying copper conductors placed above the partition in the slot take the path through the partition. As the flux lines due to current carrying copper conductors placed above the partition take the alternate path

through the partition instead of passing through the air gap and permanent magnets, the effect of armature reaction will come down.
The flux lines due to stator winding of permanent magnet synchronous generator with existing slot profile will flow through the air gap and permanent magnets when the generator is loaded. As a result the net air gap flux density will reduce because the flux lines of the current carrying copper conductors oppose the main flux lines of permanent magnets. Thus the effect of armature reaction can be observed as shown in Fig. 3 and Fig. 4 where the rms value of air gap flux density reduces from 0.624 T at no load to 0.596 T at load.
Few flux lines due to stator winding of permanent magnet synchronous generator with novel slot profile will flow through the partition provided in the slot when the generator is loaded. As a result the net air gap flux density reduces but not as much as that reduces in the case of simulation of permanent magnet synchronous generator with existing slot profile.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The advantages of the present invention will become apparent from the following detailed description of embodiments with reference to the accompanying drawings, in which:
Fig. 1 shows existing and new slot profiles of stator core of permanent
magnet synchronous generator.
Fig. 2 shows flux plot of permanent magnet synchronous generator with
existing slot profile at no load and on load.
Fig. 3 shows air gap flux density of permanent magnet synchronous
generator with existing slot profile at no load.

Fig. 4 shows an air gap flux density of permanent magnet synchronous
generator with existing slot profile at load.
Fig. 5 shows flux plot of permanent magnet synchronous generator with
new slot profile at no load.
Fig. 6 shows air gap flux density of permanent magnet synchronous
generator with new slot profile at no load.
Fig. 7 shows flux plot of permanent magnet synchronous generator with
new slot profile at load.
Fig. 8 shows an air gap flux density of permanent magnet synchronous
generator with new slot profile at load.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
Accordingly, a new slot profile of stator core of permanent magnet synchronous generator in order to reduce the armature reaction effect is proposed. The new slot profile proposed in the present invention defines a partition as shown in Fig. 1 to accommodate a certain amount of winding above the partition and certain amount of winding below the partition in the slot.
In order to ease the process of placement of copper conductors above the partition in the stator slot of permanent magnet synchronous generator, a small opening is provided in the middle of the partition as shown in Fig. 1 in addition to the slot opening provided at the inner diameter of the stator core. The width of the opening provided in the partition of stator slot must be good enough in order to insert the copper conductors through the opening.
The flux lines of winding is placed above the partition in the slot that will utilize the alternate path provided by partition in the slot as shown in Fig. 7. In order to provide an alternate

path for the flux lines of winding placed above the partition in the slot, the partition is made of stator core material. It is obvious that the effect of armature reaction in permanent magnet synchronous generator will come down as the flux lines due to current carrying copper conductors placed above the partition take an alternate path through the partition instead of passing through the air gap and permanent magnets.
The width of the opening provided in the partition of stator slot must not be more than two times the air gap for the flux lines of current carrying copper conductors to take alternate path through the partition. The lesser the value of the width of the opening, the greater will be the flux lines of current carrying copper conductors taking alternate path through the partition. Similarly the greater the thickness of the partition provided in the slot, the greater will be the flux lines of current carrying copper conductors taking alternate path through the partition but the optimized value of the thickness of the partition should be taken as the increase in the thickness of the partition beyond certain value which is not that advantageous leading to the utilization of more amount of stator core material.
The armature reaction in synchronous generators leads to two undesirable effects, distortion of air gap flux density or reduction of air gap flux density or both when the synchronous generator is loaded. When the load applied is of purely resistive type, the effect of armature reaction in the generator will be cross-magnetization leading to the distortion of air gap flux density. Similarly, when the load applied is of purely inductive type, the effect of armature reaction in the generator will be de-magnetization leading to the reduction of air gap flux density.
The permanent magnet synchronous generator with existing slot profile is simulated at no load and load by using FEM software. The load applied in the simulation is of inductive type to observe the armature reaction

effect as the reduction of air gap flux density rather than the distortion of air gap flux density. The flux lines due to stator winding of permanent magnet synchronous generator with existing slot profile will take the normal path through air gap, permanent magnets and back of the stator core as shown in Fig. 2 when the generator is loaded. As a result the net air gap flux density will reduce because the flux lines of the current carrying copper conductors oppose the main flux lines of permanent magnets. Thus the effect of armature reaction can be observed as shown in Fig. 3 and Fig. 4 where the rms value of air gap flux density reduces from 0.624 T at no load to 0.596 T at load.
The permanent magnet synchronous generator with the new slot profile is simulated at no load and load by using FEM software. The load applied in the simulation is of inductive type to observe the armature reaction effect as the reduction of air gap flux density rather than the distortion of air gap flux density. Few flux lines due to the stator winding of permanent magnet synchronous generator with new slot profile will flow through the partition provided in the slot as shown in Fig. 7. It is the flux lines of winding placed above the partition in the slot that will utilize the alternate path provided by partition in the slot while the flux lines of winding place below the partition take the normal path through the air gap, permanent magnets and back of the stator core. As a result the net air gap flux density reduces but not as much as that reduces in the case of simulation of permanent magnet synchronous generator with existing slot profile. Thus the reduced effect of armature reaction can be observed as shown in Fig. 6 and Fig. 8 where the rms value of air gap flux density reduces from 0.624 T at no load to 0.609 T at load.

WE CLAIM:
1. A modified magnet synchronous machine to reduce the armature reaction effect comprising a slot profile for a stator core partitioned to accommodate stator winding in splitted compartment connected by a narrow opening.
2. A modified magnet synchronous machine as claimed in claim 1, wherein the width of the opening is made comfortable to just receive the stator winding.

3. A modified magnet synchronous machine as claimed in claim 1, wherein the thickness of the opening is kept wide to the maximum.
4. A modified magnet synchronous machine as claimed in claim 1, wherein the partitioned slot profile creates an alternative path for the flux lines.

5. A modified magnet synchronous machine as claimed in claim 4, wherein the alternate path for the flux lines is provided by constructing the partition and stator core of same material.
6. A modified magnet synchronous machine as claimed in claim 1, wherein the synchronous machine may be a generator.
7. A modified magnet synchronous machine as claimed in claim 1,
wherein as illustrated in the accompanying drawings.