FIELD OF THE INVENTION:-
The present invention provides a per pole per phase distributed stator winding of
traction alternator for electrically isolated loads independently operable along
with a companion alternator with multiple sets of winding for plural isolated
loads.
BACKGROUND OF THE INVENTION:-
There have been four stages in the development of Diesel Locomotives with
respect to the generators employed for transferring Mechanical power of the
Diesel engine to Electrical power for driving Traction motors. Firstly, Generators
(TGs) with DC Auxiliary Generating machines (AGs) were used to convert the
mechanical power of the diesel engine to electrical power for onward
transmission to the Traction motors. However due to the usage of commutator
and carbon brushes, these TGs and its AGs required heavy maintenance and
were also prone to frequent failures leading to reduced reliability and higher
operating costs.
To improve upon the performance of the TGs Traction Alternators (TAs), with
slip rings were introduced in the second stage. This introduction reduced the
failures and increased the reliability of the alternator. Also since AC alternators
are more efficient than their DC counterparts; more powerful alternators utilizing
the same space were used to drive the Locos. As the AGs used were still DC

generators they still had the maintenance and reliability issues. The TA is used in
conjugation with DC motors and the output of TA was rectified and fed directly
to the DC motors.
In third stage the DC auxiliary generators (AGs) were replaced by the AC
Companion alternator (CA); this modification reduced the failures and increased
the reliability of the auxiliary supplies. The TA output was rectified via two
rectifier banks and directly connected in series and fed to the inverter for further
transmission to the 3 phase. Induction motors used for traction in place of DC
motors. Since the supply from TA was merged and sent to inverter at each
instance both the banks and therefore the complete alternator was uniformly
loaded at each instance.
The fourth stage of technology in Diesel locomotives in addition to the above
modifications requires the TA to supply power through rectifier to individual sets
of plurality of 3 Phase Traction motor via the converter. Thus half of the
alternator caters to plurality of motors and the other half supplies power to the
remaining plurality of traction motor. For TA to function satisfactorily while
loading is unequal between the banks, some kind of balancing arrangement had
to be devised to prevent the unbalance operation of the alternator. This new
arrangement would thus allow the alternator to supply power to plurality of
separate loads which at times may not be equally loaded and still perform
satisfactorily under the adverse conditions.
The Companion Alternator (CA) also supplies power to a number of auxiliary
loads. In order to do so the CA has multiple winding in its stator electrically
isolated from each other, so designed to withstand the variable loading subjected
in it's said various winding having variable voltage requirement without effecting

the performance. The above feature is accomplished by having a winding
configuration which isolates each of the winding sets from each other and having
a total turns ratio that enables different voltage outputs at each RPM for each of
the multiple winding sets. The above necessitates having coils which have
different turns and therefore are of different cross-sectional area. Further
because of the variable loading and variable turns of the coils, detailed study
regarding the overall flux imbalance and its effect on the machine performance
had to be investigated.
After several permutations a configuration which meets all the performance
criteria viz. voltage ratios, harmonic losses, flux distributions etc., was designed
and finalized.
OBJECTS OF THE INVENTION:-
An object of the invention is to provide an alternator with per pole per phase
distributed type of winding configuration that reduces the effect of imbalance in
the flux distribution of the alternator windings due to unequal loading.
Another object of the invention is to provide an alternator such that the main
alternator works satisfactorily under unequal loading of sets of traction motors..
Yet another object of the invention is to provide an alternator that is operable at
multiple set of loading having slight load variation.
Yet another subject of the invention is to increase the reliability of the alternator
even at unequal loading.
Yet another object of the invention is to provide a companion alternator having a
plurality of isolated winding.

A still further object of the invention is to provide a companion alternator that
supply power to multiple loads having variable loading conditions.
SUMMARY OF THE INVENTION:
The invention provides a traction alternator (TA) which provides required power
to the high horse power high torque locomotive. The main TA also provides
power to various auxiliaries with variable loadings. For this, the apparatus
includes a companion alternator (CA) that can supply power to a plurality of
auxiliary loads at different voltage levels.
The invention disclosed refers to an exemplary embodiment of the above
requirements for railways. Indian Railways in order to augment its existing fleet
of goods locomotive have introduced high horsepower high torque locomotives.
These locomotives require a Traction Alternator that is able to deliver such high
power in the space constraints as required for a traction application. However,
there can be several other embodiments of the invention. This invention is thus
the.most powerful traction alternator being used on Indian railroads. This
machine enables the locomotive to haul the heaviest loaded rakes up to about
100 Km/h.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig.l: Shows a longitudinal sectional view of the traction alternator, companion
alternator and rectifier designed according to the invention.
Fig.2: Shows the power transmission diagram of Traction Alternator.

Fig.3: CA Stator Terminal box showing different sets of windings.
Fig.4: CA Transmission diagram.
DETAILED DESCRIPTION OF A PREFERED EMBODIMENT OF THE
INVENTION:-
The following description of the invention is merely exemplary in nature and
does not limit the scope of invention.
As shown is figure 1, a longitudinal section of the apparatus is depicted. Three
separate section of the apparatus with two DC rectifier banks (013), main
traction alternator (TA) (02) and companion alternator(CA) (005) is provided.
The stator core (001) within the stator frame (002) of the TA has radial ducts for
ventilation made by I beam section spot welded on the laminations. The stator
core (001) is made up of high permeability low loss segmental laminations. The
stator core (001) is thoroughly welded by bars and pressed into sheets to
provide the required structural strength. The stator coils (003) of the TA wound
on the stator is designed with a class 200 insulation system with corona resistant
covered magnet wires insulated with mica tapes. The insulations system provides
optimal insulation design with respect to the insulation thickness, thermal
conductivity, and insulations strength. The complete wound stator thereafter
undergoes vacuum pressure impregnations (VPI) with high temperature class
vanish under controlled environment to provide a void tree, thick, insulation layer
over the stator. The VPI process also provides mechanical and structural support
to the coils.
The rotor poles (004) of the main TA is bolted onto the TA barrel by high tensile
pole bolts means. The rotor poles comprises of core held together with bars and
rivets. The core is of high tensile strength and possesses excellent

magnetic properties. It is wound under tension with covered magnet wire and
each layer is varnished by a thixotropic type of varnish.
A companion alternator (CA) (005) is provided, comprising CA stator cores (006)
that is bolted on the CA frame after it is completely wound. The stator coils (008)
are made up of corona resistant magnet wire and covered with mica tape. The
complete wound stator undergoes VPI process with a high temperature class
varnish. The CA stator is also designed as a class 200 thermal class.
The rotor poles (007) of the CA are constructed in a similar manner as that of
the main TA rotor coils. The rotor poles (007) are bolted with the CA barrel. The
TA barrel and CA barrel are spigot and bolted with each other. A shaft (009) is
shrunk to barrel. The electric power to the rotors of both main TA and CA are
supplied through the slip ring (011) and carbon brushes. The TA stator windings
passes through an end housing (014) and connects to plurality of DC rectifier
banks (013). The output of the DC rectified bank (013) is fed to the DC bus
banks by the terminals (012). The CA winding merged with auxiliary alternator of
the prior art provides plural sets of variable voltage output.
Figure 2 shows a power transmission diagram of the TA, the DC banks (11,11')
of the alternator supply power to two separate DC banks (12,12') which further
supplies power to plurality of traction motors each. The aforesaid configuration
results in unequal loading of TA banks depending upon the loading requirement
of each bank. A mechanism that enables the TA (10) to perform satisfactorily
under such conditions is required.
Figure 3 shows the CA stator terminal box where the output of the CA is taken
out in three separate phase group a first set i.e. terminals 1-2-3 are for the main

winding. The main winding in the prior art supplied power to the auxiliary
blowers, engine blowers, dust-bin blowers etc., in addition to supplying power to
the rotor of main TA. The invention provides the first set of windings that
supplies power to the all the aforesaid excluding the main TA rotor. The second
set, terminal 4-5-6, comprises of half tap winding which is controlled after
rectification and fed to the rotor of main TA. The third isolated set of winding is
the Auxiliary winding terminal 7-8-9, designed to eliminate the requirement of a
separate auxiliary alternator as used in the prior art. In the prior art, a gear train
driven separate auxiliary alternator was used to supply power to the control and
other circuits. Due to the additional set up and related maintenance involved, a
scheme was developed to eliminate the additional apparatus. The scheme was to
design a companion alternator (CA) (005) in such a way that in addition to
performing its current function it also caters to the functions of the auxiliary
alternator.
The CA (20) having plurality of windings in its stator eliminates the involvement
of an additional machine which further reduces the cost of maintenance and area
consumption. The efficiency is improved due to removal of gear train of the
auxiliary generator.

WE CLAIM:-
1. An apparatus comprising:
an alternator (10) of per pole per phase distributed stator winding
wherein the complete wound stator undergoes vacuum pressure
impregnation;
a companion alternator (005) merged with auxiliary alternator having
plurality set of winding for variable voltage operation;
at least two rectifier banks (013);
characterized for reducing the unbalance effect in the flux distribution of
alternator winding at unequal loading.
2. The apparatus as claimed in claim 1, wherein the alternator is a traction
alternator (02).
3. The apparatus as claimed in claim 2, wherein the dual DC banks of the
alternator supply power to a separate dual dc banks which supplies power
to each of the plurality of traction motors.
4. The apparatus as claimed in claim 3, wherein the separate dual dc banks
supplies power each of the plurality of traction motor.
5. The apparatus as claimed in claim 1, wherein the operation of the
Companion Alternator is taken out in three separate phase groups.

ABSTRACT

The present invention is provided with an apparatus comprising an alternator
(02) of per pole per phase distributed stator winding wherein the complete
wound stator undergoes vacuum pressure impregnation; a companion alternator
(005) merged with auxiliary alternator having plural sets of winding for variable
voltage operation; at least two rectifier banks (013); characterized for reducing
the unbalance effect in the flux distribution of alternator winding at unequal
loading.