FILED OF INVENTION:
The present invention relates to the field of traction alternators for diesel electric
locomotives in general and to companion alternator for catering electrical load to
auxiliary drives of diesel electric locomotive in particular.
BACKGROUND AND PRIOR ART:
In a diesel electric locomotive, mechanical power developed by the diesel engine is used
to drive an alternator which generates 3 phase AC output. This AC power is then
rectified to DC power which drives the traction motors of the locomotive, which are all
DC traction motors. Typically, a diesel electric locomotive of 3600 HP rating has 6 DC
traction motors which are driven in 2 series and 3 parallel and also in 6 parallel modes.
At present in a diesel electric locomotive, the diesel engine drives all major auxiliaries
like radiator fan which are driven through eddy current clutch and auxiliary
generators/exciters of alternator through gear train arrangement or belts. Power to the
eddy current clutch & auxiliaries (driven system) are transmitted through mechanical
engagement with engine crankshaft or alternator shaft (driver). Hence, they consume
power irrespective of their requirement during idling or on load.
The present invention seeks to overcome this drawback of the prior art.
In the proposed locomotive of 3600 HP, all auxiliary except compressor are electrical
driven, which switch on and off as and when required at predefined multi setting speed.
Thus proposed arrangement will save energy by optimum utilization of auxiliaries
besides providing flexibility in their physical layout. The controls of proposed locomotive
have changed considerably due to replacement of DC machine namely exciter &
auxiliary generator by the companion alternator, which is an AC machine. This has
completely changed the controls for cranking, excitation of main alternator, battery
charging and generation of 72 V control supply beside control of motors of radiator fan
& traction motor blowers. The state of art microprocessor based control system

proposed regulates gross power produced by diesel engine at site condition, instead of
fixed traction input in conventional controls of the prior art. Since the auxiliaries are
used efficiently and selectively as per their need, the remaining power is used by
traction. Hence, input to traction power is maximized resulting in energy efficient
system.
OBJECTS OF INVENTION:
It is an object of the present invention to provide an improved traction alternator having
a built-in companion alternator which will cater to electrical load of the auxiliary drives of
the locomotive.
Another object of the invention is to provide an improved traction alternator having a
built-in companion alternator which will facilitate replacing the mechanically driven
auxiliaries by electrically operated auxiliaries.
Yet another object of the invention is to provide a neat layout of AC driven auxiliaries
instead of mechanical driven auxiliaries for ease of maintenance.
A further object of the present invention is to provide an improved traction alternator,
thereby reducing the cost of maintenance and increasing the overall efficiency of the
locomotive engine.
DESCRIPTION OF THE INVENTION:
The 1100V AC/DC power transmission is being proposed for the new locomotives, i.e.
mechanical power output of the diesel engine will be converted to 3 phase electric
power by the traction alternator, which will be rectified by the alternator mounted diode
rectifier bridge and fed to the 6 DC traction motors. The traction motors are operated in
2 series and 3 parallel & 6 parallel, combinations.
Traction alternator excitation control is proposed to be microprocessor controlled based
upon master controller feedback of diesel engine notch and loading condition. A
thyristorised bridge will be used for control of traction alternator excitation, the firing

pulses for which will be generated by the microprocessor, based upon load current,
system voltage and other system parameters feedback.
The companion alternator is mechanically coupled with the diesel engine and is excited
from fixed 72 V from the control voltage supply with battery backup. Therefore,
companion alternator produces variable voltage & variable frequency supply depending
upon engine speed with fixed V/F ratio. Thus, the power produced by the auxiliary
motors fed from output of companion alternator is always proportional to speed of diesel
engine as in the existing system. Companion alternator output is fed to radiator fans,
traction motor blowers, main alternator excitation, battery charger & local control
supply.
The control supply of 72 V is generated using rectifier chopper module fed from
companion alternator, the output of which is also used for battery charging. Control
pulses for the chopper will be generated by the microprocessor based controller so as to
generate a constant control supply output.
The main alternator of the newly designed machine is based on innovative modifications
carried out based on experience of the site performance of proven alternators. However,
the gearbox and the auxiliary generators are eliminated in the novel configuration.
Hence the improved traction alternator is free from the present problematic aspects, viz.
gear trains and oil leakage from auxiliaries etc.
The slip ring assembly has been kept outside the bearing housing and the end-shield in
order to have easier access for change of carbon brush. Such a design will also be
further beneficial as no carbon dust will enter inside machine, which in turn will increase
the coils and insulation life due to no deposit of carbon dust and oil. Thus the new
alternator will give trouble-free service without much maintenance involved.

DESCRIPTION OF THE ACCOMPANYING DRAWING:
Fig. 1 shows the details of the traction alternator with the companion alternator in
accordance with the invention.
The invention will now be described in detail with the help of an exemplary embodiment
as depicted in the accompanying drawing. However, there can be many other
embodiments of the invention, all of which are deemed covered by this specification.
The main alternator (01) has main alternator rotor (04) which is mounted co-axially on
the same shaft with the companion alternator (02) which has companion alternator rotor
(05). The rotor hub (10) of the main alternator is joined to the rotor hub (11) of the
companion alternator by means of bolt (06) so that both alternators (01,02) must rotate
together. Both alternators have a common stator frame (07) to which end shield (08) is
attached . Slip ring assembly (14) and brush gear assembly (09) are placed outside
endshield (08) for the purpose of easy maintenance and replacement of brushes. It also
prevents conductive carbon dust from the brushes form entering inside the machine.
The ventilation of the main alternator (01) as well as the companion alternator is
provided by a fan (03) which is mounted on the same shaft as that of the alternators,
and provides self-ventilation for both alternators.
The companion alternator will deliver the electrical load requirement of AC driven
auxiliaries, engine lighting, battery charging etc. Output of the companion alternator will
also cater for the main alternator excitation.
The main alternator rotor (04) and companion alternator rotor (05) are designed in two
parts for ease in manufacturing and maintenance. The alternator rotor parts are then
spigoted and bolted together to form a single shaft.
Input to traction can be optimized depending upon duty cycle of auxiliaries.

The following auxiliaries of the locomotive shall be electrically driven with AC motors
instead of mechanical drive which will enable control of duty cycle as per need
The auxiliaries shall be directly supplied from the companion alternator output and as
per output frequency of the companion alternator at different engine seed. Accordingly
speed of auxiliaries will vary in direct proportion to engine speed. This is being adopted
on the basic principle that the output from auxiliaries are required to vary almost in
proportion to engine speed.
The electrically driven auxiliaries shall be:
a) Radiator fan:
The radiator fan motor shall 3 phase AC with dual speed through pole changing
principle (1/2 and full speed). As per cooling requirement of engine based on engine
cooling water temperature, the radiator fan speed shall be set to either 1/2 speed or
full speed. However, when the radiator fan is switch on, the 1/2 or full speed shall be
as per the prevailing frequency output of companion alternator. Each loco shall have
a single 90 HP radiator fan. Hence total cooling of engine can be varied in 1/2and full
by switching the motor at 1/2 or full speed as required.
b) Traction motor blower:
Both front traction motor blower (FTMB) & rear traction motor blower (RTMB) shall
also be of dual speed through pole changing principle (1/2 and full speed). The
speed combination shall be decided based on feedback of motor temperature
calculated by I2 RT principle (without any physical sensor). Hence, the control system
shall be more reliable without any sensor or connecting wires to the motors. As in
case of radiator fan, the blower speed will be in direct proportion of engine speed as
in existing mechanical drive system.

However, electrical drive blowers will be more efficient, can be switched on/speed
can be varied based upon requirement (not all the time as in existing system) and
can be physically located freely any where (as it is not connected to engine shaft as
in existing system).
Total load requirement of companion alternator is 215 HP.
Constructional features of the improved traction alternator
The basic construction features of the new alternator are as under:
i. STATOR
Low loss high quality electrical sheet steel segmental punchings are built on
insulated stator core studs between core end plated which are welded to stator
ribs inside the stator frame. The frame is a rolled steel barrel with axial and
circumferential reinforcing steel ribs. Coupling lugs, lifting lugs and resting
flanges welded on to it.
The main alternator is a 10-pole, 2-layers, 3-phase, star connected, wave
winding with two parallel circuits per phase, is housed in open type stator slots.
Single turn stator coils are Class H class insulated. The frame is designed in
such a way that, it houses both main & companion alternator core and winding
respectively at non-driving end and driving end of the alternator.
The three terminals of the stator winding are brought out through the cut-outs in
frame in the form of copper bus-bars for connection of top mounted rectifier.
The neutral connection is also brought out to terminal box to facilitate the
connection of ground relay and better ground fault protection.

The fabricated end-shield (Fig. 1, Item 08) is spigoted and bolted to the stator.
Four large air-inlet cum inspection opening with perforated covers, have been
provided on the end shield to facilitate inspection and maintenance in mounted
on the end shield.
ii. ROTOR
The rotor hub is a steel barrel that is made in 2 parts, namely main alternator
rotor hub (10) and companion alternator rotor hub (11). On the driving end side
companion alternator rotor hub is positioned on which main alternator rotor hub
is bolted and spigoted. On the non-driving end along with main alternator rotor
hub (10) a shaft extension and disc assembly (12) is spigoted and bolted. The
10 laminated rotor poles of main and 16 laminated rotor poles of companion
lternator are mounted on the respective round rotor hub and bolted from inside
of the rotor hub. The fan 3 is spigoted and bolted onto the rotor hub on driving
end. The rotor assembly is solidly coupled to the diesel engine crank shaft and
the other end of the shaft supported on a cylindrical roller bearing houses in the
end shield
The Class 'H' insulated Field Coils are of edge-wound design, made out of a
continuous copper strip. Coil to coil connections are of brazed type. The field
connections are supported on a common tie-ring, which is firmly secured to the
rotor hub.
The alternator fan has a ring gear (Fig. 1, Item 13) on fan outer diameter so that
cranking can be done through ring gear by using 2 Nos. Delco Remi starter
motors.
The gear box and gear trains of traction alternator is also eliminated so that no
wear & tear problem of these components arise.

The traction alternator with a built-in companion alternator in accordance with
the invention as described herein has the following main advantageous
distinguishing features over the prior art:-
1. It has common self-ventilating shaft-mounted fan which is accommodated
within its frame (07). This dispenses with the need to provide separate
cooling fan which is placed on the locomotative floor in the prior art, leading
to valuable saving of floor space.
2. It saves considerable power for the auxiliaries during idling or low-speed
operations because the companion alternator delivers only the requisite
amount of auxiliary power.
3. It provides for easier maintenance and replacement of brushes as the
slipring and brush gear assemblies are located outside the housing.
4. It provides for longer operational life because entry of carbon dust from the
brushes is prevented.

WE CLAIM:
1. A traction alternator for diesel electric locomotives with AC auxiliaries
Comprising:
- main alternator (01) having a rotor (04), companion alternator (02)
having a rotor (05), self-ventilated fan (03), common stator frame (07),
and shield (08), brush gear assembly (09), main alternator rotor hub
(10), companion alternator rotor(ll) and slip-ring assembly,
characterized in that the main alternator (01), the companion alternator
(02) and the ventilating fan (03) are rigidly mounted on the same shaft.
2. A traction alternator as claimed in claim 1, wherein main alternator (01) and
companion alternator (02) have a common stator frame(07).
3. A traction alternator as claimed in claim 1, wherein main alternator rotor hub
(10) is joined with companion alternator rotor hub (11) through bolt (06).
4. A traction alternator as claimed in claim 1, wherein the slip-ring assembly (14)
and brush gear assembly (09) are located outside the bearing housing and the
end shield (08).

A traction alternator for diesel electric locomotives with AC auxiliaries Comprising:
- main alternator (01) having a rotor (04), companion alternator (02) having a rotor (05), self-ventilated fan (03), common stator frame (07), and shield (08), brush gear assembly (09), main alternator rotor hub (10), companion alternator rotor(11) and slip-ring assembly,
characterized in that the main alternator (01), the companion alternator (02) and the ventilating fan (03) are rigidly mounted on the same shaft.