The present invention relates to electrical machines and in
particular to the permanent magnet alternator. More particularly, the invention is
related to a multiple output permanent magnet alternator and the utilization of
two technologies, radial flux permanent magnet technology and axial flux
permanent magnet technology in it.
BACKGROUND OF THE INVENTION
In US3809995 patent, a multiple output alternator having separate
sets of power coils mounted on the stator adapted to be magnetically excited by
a rotor having a direct current field coil is proposed. The multiple output
alternator proposed in US3809995 patent can provide two different voltage levels
as two separate sets of power coils are mounted on the stator but the frequency
of the two voltages will be same. The power electronic equipment is very much
needed if the multiple output alternator proposed in US3809995 patent has to
provide the voltages with different frequencies.
Therefore, the object of the invention is to provide an alternator
three AC outputs of different voltages and frequencies by utilizing both the radial
flux permanent magnet technology and axial flux permanent magnet technology.
Thus in the present invention, a multiple output hybrid PM alternator with an

approach to use both the radial and axial flux permanent magnet technologies is
proposed by suggesting a new rotor structure and a modification to the end plate
of the stator frame of the multiple output hybrid PM alternator.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to propose a multiple
output hybrid PM alternator with three AC outputs of different voltages and
frequencies.
Another object of the invention is to propose an approach for
utilizing both the radial axial flux permanent magnet technologies in the multiple
output hybrid PM alternator.
Yet another object of the invention is to increase the power density
of the proposed multiple output hybrid PM alternator.
SUMMARY OF THE INVENTION
According to the invention, a multiple output hybrid PM alternator
with an approach for utilizing both the radial flux permanent magnet technology
and axial flux permanent magnet technology is proposed in order to have three
AC outputs of different voltages and frequencies along with increased power

density by suggesting a new rotor structure and a modification to the end plate
of the stator frame of the alternator.
The multiple output hybrid PM alternator is significant in that it is
based on both the utilization of radial flux permanent technology and axial flux
permanent magnet technology with a rotor carrying both the radial and axial flux
permanent magnets and endplates carrying axial stator cores as shown in Fig.l.
The multiple output hybrid PM alternator is also significant in that
the rotor structure is carrying axial flux permanent magnets on both the end
sides while it is carrying radial flux permanent magnets over the cylindrical
surface as shown in Fig.2.
The multiple output hybrid PM alternator is also significant in that
the axial stator cores are integrated to both the end plates of the stator frame as
shown in Fig.3.
The multiple output hybrid PM alternator is also significant in that
the axial stator core on the end plate and axial permanent magnets over the
rotor core can be arranged without extending the over all length of the generator
much by utilizing the space, available because of radial stator winding overhang,
between the end plate and the rotor core.
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.l is a view of 3D model of multiple output hybrid PM alternator
utilizing radial flux permanent magnet technology and axial flux permanent
magnet technology.
Fig.2 is a view of 3D model of rotor core of multiple output hybrid
PM alternator carrying radial and axial flux permanent magnets.
Fig.3 is a view of 3D model of axial stator core integrated to the
end plate of multiple output hybrid PM alternator stator frame.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
The power electronic equipment is very much required when the
alternator, capable of providing certain voltage level with certain frequency, has
to supply power to the load that needs voltage level or frequency other than the
rated voltage and rated frequency of alternator. At the same time, the power
electronic circuit will also become complex if the alternator is to be provided with
multiple outputs of different voltages with different frequencies. In the present
invention, a multiple output hybrid PM alternator to provide three AC outputs of

different voltages and frequencies is proposed in order to avoid the power
electronic equipment.
The multiple output hybrid PM alternator proposed in the present
invention utilizes both the permanent magnet technologies, radial flux permanent
magnet technology and axial flux permanent magnet technology in order to
provide three AC outputs of different voltages and frequencies. The use of both
the radial and axial flux permanent magnet technologies in the present invention
also results in the increase of the power density of alternator. According to the
aspect of the invention, an approach for utilizing both the radial flux technology
and axial flux technology is proposed in the multiple output hybrid PM alternator
by suggesting a new rotor structure and a modification to the end plates of the
stator frame.
The 3D model of multiple output hybrid PM alternator as shown in
Fig.l is peculiar in consisting of a rotor core (100) carrying both the radial flux
permanent magnets and axial flux permanent magnets and end plates (180)
carrying axial stator cores (200). Only end plates of the stator frame of multiple
output hybrid PM alternator are shown in Fig.l without showing the stator frame
in order to view the inside structure.
The axial flux permanent magnets (80) are glued to the rotor
structure (150) on both the end sides while the radial flux permanent magnets
(90) are inserted in the slots made along the length of the rotor core (160)
circumferentially as shown in Fig.2. Though the rotor structure (150) shown in

Fig.2 is of insertion type for the radial flux permanent magnets (90) for
illustration of concept, the rotor structure (150) of surface mounted type for the
radial flux permanent magnets can be used.
The multiple output hybrid PM alternator is significant in that the
axial stator cores are integrated to both the end plates of the stator frame as
shown in Fig.3. The multiple output hybrid PM alternator is also significant in that
the axial stator core on the end plate and axial permanent magnets over the
rotor core can be arranged without extending the over all length of the generator
much by utilizing the space, available because of radial stator winding overhang,
between the end plate and the rotor core.
Thus a multiple output hybrid PM alternator can also be made to
work as a single output hybrid PM alternator. Though 10 radial permanent
magnet poles over the circumference and 10 axial permanent magnet poles on
each end side of rotor core are taken in the 3D model of multiple output hybrid
PM alternator along with 45 slots in the radial and axial stator cores, the number
of poles and slots can be varied as per the design requirement in order to have
different frequencies. Thus the proposed multiple output hybrid PM alternator
can be made to provide three AC outputs of different voltage levels and
frequencies by appropriate selection of number of poles and number of turns in
the stator winding and other parameters. Though the 3D model of multiple
output hybrid PM alternator shown in Fig.l is fractional slot type, it can also be

designed as integral slot type and even concentrated windings can also be used
instead of distributed winding.
Two more axial flux permanent magnet alternators with over all
diameters less than the diameter of radial rotor core accommodated on either
side of the radial rotor core can provide reasonable amount of auxiliary power for
various auxiliary equipments operating at voltage and frequency other than
voltage and frequency of the main radial flux permanent magnet alternator.
Thus in the present invention, an approach for utilizing both the
radial flux permanent magnet technology and axial flux permanent magnet
technology in the multiple output hybrid PM alternator is proposed in order to
have three AC outputs of different voltages and frequencies. As an additional
consequence of the present invention, the proposed multiple output hybrid PM
alternator has got increase in the power density.

WE CLAIM
1. A multiple output hybrid PM alternator, which utilizes both the radial and
axial flux permanent magnet (80,90) technologies comprising:
a rotor (150) carrying both the radial and axial flux permanent
magnets (80, 90);
end plates (180) carrying axial stator cores;
in order to achieve three AC outputs of different voltages and
frequencies.
2. The multiple output hybrid PM alternator as claimed in claim 1, wherein
the rotor structure is carrying axial flux permanent magnets on both the
end sides while it is carrying radial flux permanent magnets over the
cylindrical surface.
3. The multiple output hybrid PM alternator as claimed in claim 1, wherein
the axial stator cores are integrated to both the end plates of the stator
frame.
4. The multiple output hybrid PM alternator as claimed in claims 3 and 4,
wherein the axial stator core on the end plate and axial permanent

magnets over the rotor core can be arranged without entending the over
all length of the generator.
5. The multiple output hybrid PM alternator as claimed in the preceding
claims, further achieves an increase in the power density.