FIELD OF THE INVENTION
The present invention relates to a brushless alternator for high power Diesel
Electric Multiple Unit (DEMU).
BACKGROUND OF THE INVENTION
Self-propelled High Power Diesel Electric Multiple Unit (HHP DEMU) with the
ratings of 350HP, 700HP & 1400HP are known. These DEMUs are normally
having one driving power car (DPC) and three Trailer Cars. The driving power car
(DPC) is powered with a Diesel Engine, and an AC/AC transmission system. The
engine is coupled to a traction alternator, and mounted in the longitudinal
direction on the floor of the power car. The alternator is used for providing
power supply on continuous basis as per DEMU application including operating
site conditions, for example, wide temperature range like 0°C to 55°C, humidity
from 40% to 100%, high limits of noise, vibration, heat & exhaust gases, heavy
rainfall and high flood water level.
The consumers are now aiming at new DEMU system with at least 1600HP
ratings. For this application there is a requirement of high voltage and low
current rated alternator. It is also required that the alternator is enabled to
deliver power for a maximum operating speed of 100 kmph. The application
further requires a compact size of alternator with reduced size and weight, so
that there is ample space available in the driving power car (DPC) for other
equipments.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a traction alternator for a
self-propelled 1600HP High Power Diesel Electric Multiple Unit (HHP DEMU).
Another object of the invention is to propose a traction alternator for a self-
propelled 1600HP High Power Diesel Electric Multiple Unit (HHP DEMU), which is
a light weight and compact brushless alternator.
A further object of the invention is to propose a traction alternator for a self-
propelled 1600HP High Power Diesel Electric Multiple Unit (HHP DEMU), which
inter alia allows development of traction alternators with higher ratings of
1020KW, 1333V, 502 Amps, 1800 RPM adaptable to the self propelled 1600HP
High Power Diesel Electric Multiple Unit (HHP DEMU).
SUMMARY OF THE INVENTION :
Accordingly, there is provided a higher rating brushless alternator for a self
propelled 1600HP High Power Diesel Electric Multiple Unit (HHP AC-AC DEMU).
The alternator is applicable under various load conditions of traction at all
notches of the diesel engine.
According to the invention, a stator frame is developed with tubular construction,
which consists of a plurality of ribs and sheet to make the frame sturdy and light
in weight. The frame, pedestal plates and end-shields are configured to allow
easy assembly/disassembly of the alternator. Lifting lugs are installed on the
frame for lifting with a conventional overhead hoist. A removable drip-proof,
louvered cover in two halves encloses the exciter and rotating rectifier bridge.

The brushless alternator of the invention is of compact size with a high power to
weight ratio of 0.3188 (approx.) and is suitable for coupling and aligning with
diesel engine. A capsule type wound stator is provided for the alternator, which
is produced by assembly of punchings and putting stator coils in the stator slots.
The alternator is having an auxiliary exciter and diode wheel assembly mounted
on a single shaft between the bearing arrangements to make the alternator
brushless. The alternator parameters are optimized for achieving required
performance of the self propelled 1600HP High Power Diesel Electric Multiple
Unit (HHP DEMU).
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Table I - Shows the constituent components list with reference
numerals.
Table II - illustrates a comparison of winding diagram between the
prior art and the invention.
Figure 2 - illustrates a sectional diagram of the brushless traction
alternator of the invention displaying all the components.
Figure 3 - illustrates outline diagram of the brushless traction
alternator displaying mounting arrangement of the
alternator.

The invention will now be described in detail in an exemplary embodiment as
depicted in the accompanying drawings. There can however be other
embodiments of the same invention, all of which are deemed covered by this
description.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Detailed description of different major components used in this preferred
embodiment are listed in table-1 and shown in figure - 2.
Stator Core Assembly:
The stator laminations (2) are manufactured from one piece low loss magnetic
steel in a die and punch. These stator laminations are stacked together with the
help of a plurality of core clamping plates (5) at both ends to assemble the stator
core (3).
Stator coils (1) are manufactured with "class-H" insulation system in which best
quality insulated copper and insulating materials like inter-turn insulation, ground
insulation etc. are used. These coils are made on a former with multiple number
of turns and consolidated together, are further checked by inserting in a cradle.
After final manufacturing, these stator coils are housed in stator slots of the
stator core and joined together to make the winding 3-phase which are
electrically 120 degree apart from each other.

To make easier joints of various phases, at least four connection rings (9) are
provided (3-phases R, Y, B & one neutral ring). From these connection rings,
three terminals are brought out and terminated in the terminal box with the help
of three bus bars R, Y, & B (13).
Magnet Frame:
The complete stator core assembly (3) which is called capsule, is then insulated
in solventless resin for consolidation of the insulation system.
This stator capsule (3) is then inserted in a magnet frame (4), which has a
tubular construction. The magnet frame is configured as robust and light in
weight. Two lifting lugs (8) are provided in the magnet frame (4) for lifting of the
alternator with a conventional over head hoist during handling of the alternator.
Rotor Assembly:
Rim punching assembly (15) is built up by stacking of rim punchings, which are
made of one piece low loss magnet steel with the help of end punchings at both
ends and tightened under pressure. This rim punching assembly is shrink-fitted
on the rotor shaft (14) and comprising a dovetail groove arrangement in which a
pole and coil assembly (16) is fitted. These pole and coil assembly comprises a
pole assembly and a field coil assembly.
The pole assembly is made up of steel laminations which are retained from both
ends by a plurality of pole end plates and field coils assembly includes field
copper and its insulation. Taper keys are used to lock the pole and coil assembly
in the dovetails of the rim punching assembly. After disposing of the pole and

coil assemblies in their respective positions, all field coils are connected in series
by joining copper connectors with nuts and bolts.
Bearing assemblies and End shields :
The rotor assembly is placed in the capsule assembled magnet frame with two
bearing assemblies (10-11) one each at DE and NDE sides. These bearings
(10,11) are housed in a bearing housing and in turn in respective end shields (6-
7).
Exciter:
The exciter along with diode wheel assembly is basically a conventional DC
generator, which has stationary field coils and during service AC is induced in its
armature which has 3-phase winding and mounted on the same shaft of the
main alternator rotor on which the rim punching assembly is fitted.
The exciter stator core is made up of low loss sheet steel laminations, which has
salient pole type configuration. These laminations are stacked together to form
the exciter stator core. The field coils which are insulated copper wires are
placed on the salient poles. After placement on the salient poles, these field coils
are joined together in series by brazing the coil leads and this complete exciter
stator assembly (12) is VPIed with solventless resin.
The exciter armature core is also made of low loss sheet steel laminations which
are stacked together and armature coils of enamelled copper are placed inside
the slots of the core and joined together in the form of a 3-phase winding. This

exciter armature assembly (18) is placed on the shaft of the main alternator with
a sleeve means.
Rotating rectifier Bridge:
Rotating rectifier Bridge (19) is a full wave rectifier bridge made of six semi-
conductor devices mounted on aluminum heat sinks and mounted on the shaft of
the main alternator. These semi conductor devices are retained in the heat-sink
assemblies with retaining nuts and washers.
During operation of the alternator, the three phase voltage generated in the
exciter armature assembly (18) is applied directly to the Diode wheel assembly
(19). The Rotating Rectifier Bridge (19) rectifies the 3-phase alternating current
supplied by the exciter armature assembly (18) in to DC current, which is fed to
the main alternator rotor field.
Fan and Pulley:
In this alternator, a fan (17) is provided at the drive end to make the alternator
self-ventilated. The alternator is cooled during service by circulating cooling air
through the machine. Ambient cold air is drawn into the machine through
louvered openings at the exciter end of the machine and exhausted to
atmosphere from drive end. A pulley (22) is provided on the NDE side to operate
other auxiliary alternator, which is used to fed the supply to the other electrical
equipments like air conditioner, light, fans etc. in the compartments.

WE CLAIM :
A Brushless Alternator for High Power Diesel Electric Multiple Unit (HHP DEMU),
comprising :
an alternator stator core (3) built up of one-piece low loss steel
laminations (2), which are assembled under pressure applied by a
plurality of core clamping plates at both ends to form the stator core
(3), the stator core (3) being rigidly fixed on to a stator frame (4) by a
key;
a plurality of stator coils (1) with class insulated placed in
corresponding stator slots and connected to form a 3-phase winding,
the coil leads brought out to at least four connection rings (9) (three
phases R, Y, B and one neutral ring), and a plurality of Bus-bars (13)
bolted to the rings (9) and brought out in a terminal box,
a rotor core made from one piece low loss rim punchings, which are
stacked together under pressure and fitted on a shaft (14) with a key,
the pole punchings being of salient pole construction, are stacked
together by a plurality of pole end plates at both ends to form a pole
assembly, the pole and coil assembly (17) thus formed is locked in a
dovetail groove of a rim punching assembly (15) by tapered keys;
an exciter consisting of a stationary field assembly (12) and a main
rotor assembly comprising a rotating exciter armature (18) and a
Diode Wheel assembly (19), the exciter field assembly (12) comprising
poles assembled along-with their field coils are bolted to the NDE end-
shield (11); and

a rotating rectifier bridge (19) comprising a full wave rectifier bridge
and the exciter assembly (18) are sleeve mounted on the shaft inside a
bearing assembly NDE (11) for stability and reducing vibrations.
2. The brushless alternator as claimed in claim 1, wherein the ratings of
the alternator is 1020 KW, 1333 V, 502 Amps at 1800 RPM.
3. A Brushless Alternator for High Power Diesel Electric Multiple Unit (HHP
DEMU), as substantially described and illustrated herein with reference
to the accompanying drawings.

The invention relates to a Brushless Alternator for High Power Diesel Electric
Multiple Unit (HHP DEMU), comprising : an alternator stator core (3) built up of
one-piece low loss steel laminations (2), which are assembled under pressure
applied by a plurality of core clamping plates at both ends to form the stator core
(3), the stator core (3) being rigidly fixed on to a stator frame (4) by a key; a
plurality of stator coils (1) with class insulated placed in corresponding stator
slots and connected to form a 3-phase winding, the coil leads brought out to at
least four connection rings (9) (three phases R, Y, B and one neutral ring), and a
plurality of Bus-bars (13) bolted to the rings (9) and brought out in a terminal
box, a rotor core made from one piece low loss rim punchings, which are stacked
together under pressure and fitted on a shaft (14) with a key, the pole punchings
being of salient pole construction, are stacked together by a plurality of pole end
plates at both ends to form a pole assembly, the pole and coil assembly (17)
thus formed is locked in a dovetail groove of a rim punching assembly (15) by
tapered keys; an exciter consisting of a stationary field assembly (12) and a main
rotor assembly comprising a rotating exciter armature (18) and a Diode Wheel
assembly (19), the exciter field assembly (12) comprising poles assembled along-
with their field coils are bolted to the NDE end-shield (11); and a rotating
rectifier bridge (19) comprising a full wave rectifier bridge and the exciter
assembly (18) are sleeve mounted on the shaft inside a bearing assembly NDE
(11) for stability and reducing vibrations.