FIELD OF THE INVENTION
The invention relates to an improved 850 kW, 3-phase induction
motor adaptable to 6000 HP electric locomotives.
BACKGROUND OF THE INVENTION
In the recent years, Indian Railways have introduced 6000 HP electric
locomotives with 3 phase drive technology for freight application. In
these locomotives, the hauling is done with 3 phase induction motors
instead of DC series motors. The motors are operated with variable
voltage variable frequency supply from the converter-inverter bank.
These induction motors are of 850 kW rating with very compact
design and insulation of high temperature class i.e. Class 200
resulting in a high power to weight ratio.
These locomotives are in service for the last 10-12 years and in this
period many cases have been experienced in which the locomotive
have not been able to start with required load at up gradients due to
inadequate torque produced by the motors in the locomotive.

The starting torque of electric locomotive, generated by the existing
850 kW, 3 phase induction motor is not adequate, when the loaded
train is standing at an up gradient and due to this inability, the
locomotive does not perform the basic function of hauling the train
for which it is meant.
Electric locomotives are used to haul passenger and freight traffic in
the service of rail systems. Each locomotive has 2-6 motors which
produce the hauling power in the locomotive. In the existing
locomotives. DC series motors are used for this purpose due to good
characteristic of the motor suitable for traction application. Now with
development of the improved 3 phase drive technology and easier
control of the induction motors to achieve desired characteristic, the
DC series motor is being replaced with 3 phase induction motors.
These motors are driven by 3 phase variable voltage variable
frequency supply from a converter housed inside the locomotive.
Based on the supply from converter, the motor rotates producing
required torque at different speeds matching with the speed
condition of the locomotive so that the train runs smoothly picking up
speed up to the desired level. Specially when the loaded train is
standing at an up gradient, the starting torque requirement is higher
and if the motors are not able to produce this higher torque, the train
does not move.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved 850
kW, 3 phase induction motor, adaptable to 6000 HP electric
locomotives.
Another object of the invention is to propose an improved 3 phase,
850 kW induction motor for freight application in 6000 HP electric
locomotives.
Yet another object of this invention is to propose an improved 850
kW, 3 phase induction motor which eliminates the problem of
inadequacy in the starting torque required at high gradients services.
A further object of this invention is to propose an improved 850 kW,
3 phase induction motor which can be fitted and replaced easily on
and from the same mounting hole of the existing set up.
SUMMARY OF THE INVENTION
Accordingly there is provided an improved 850 kW, 3-phase induction
motor adaptable to 6000 HP electric locomotives, in particular for

freight hauling at high gradients locations. The motor comprises a
stator having stator core formed of sheet steel lamination, a plurality
of punched slots of size 500 mm and above, being configured along
the length of the stator. The stator coils have at least eight number
of turns placed inside the plurality of punched slots to form the 3
phase winding, the supply terminals projecting out of the stator
windings. A rotor having a shaft including a plurality of sheet steel
punching retained at both ends of the shaft by end plates. The
punchings accommodate rotor bars, the ends of the rotor bars being
joined via a shorting ring to form a cage construction such that the
rotor and the stator are operably compatible. And a rotor suspension
means is provided on the axle enabling mounting of the improved
motor on the existing axle , the roller suspension means comprising a
suspension tube, a bearing, and the axle with road wheels .
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 illustrates torque-speed characteristics of the existing and the
improved 3 phase induction motor having higher stating torque.

Fig. 2 illustrates sectional diagram of the improved 3 phase induction
motor displaying all the components.
Fig. 3 illustrates the mounting arrangement of the improved 3 phase
induction motor.
Fig. 4 illustrates the modified stator frame construction according to
the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The higher staring torque feature in the motor, according to the
invention, has been achieved by changing the electrical parameters
of the existing motor through extensive experimentation and pre-
assessment of the torque-speed characteristics.
As illustrated in Fig 2, the stator core (5), made of sheet steel
laminations, are stacked together to form a complete stator
construction. The length of the laminated core (5), having punched
slots, have been increased from 480mm to 500mm as per the
invention.

Coils (1) of insulated copper performer which are placed inside the
slots in core and joined together in the form of a 3-phase winding.
The stator coils, which have multiple number of turns, are
consolidated together before insertion in to the slots.
As per the invention, the number of turns of the stator coil has been
changed to 8 compared to the existing 9 in art.
The supply terminals (10) of the stator winding are brought out for 3-
phase electrical supply to the motor.
The rotor (4) of the motor has a shaft (3) including a set of sheet
steel punching (9) which are mounted and retained from both ends
by end plates (8). The punching (9) have slots in which rotor bars (6)
of copper are inserted on each side of the rotor, the ends of rotor
bars are joined together by brazing through a shorting ring of copper
so that the rotor bar (6) and the shorting ring form a cage
construction. Rotor construction has accordingly been changed to
establish a compatibly with the stator.
The roller suspension arrangement on an axle (13) as illustrated in
Fig 3, makes it possible for the motor (1) to be mounted on the
existing axle without any change in the bearing components (12).

The increased length of the inventive motor (17) has been
accommodated in the same roller suspension bearing device of the
motor (16) of the prior art.
The mounting device comprises the axle (13) with road wheels (14)
on both sides, a suspension tube (18), a bearing and the associated
components (14) which are bolted to the motor (17) by at least 8
nos. of bolt.
The PCD of holes for mounting of the above arrangement has been
kept same by modifying the stator chamber (15) as illustrated in Fig
4.
Hence , the motor (17) can be mounted on the existing bogie without
any change in the suspension tube (18) and the bearing components
(14).
Depending on the choice of the stator core, stator coil, rotor core and
rotor construction, the torque produced by the motor (17) at
different speeds have been recorded.
Therefore, the present invention proposes a synchronization of these
parameters to achieve the desired torque at the starting including the
continuous torque produced by the developed motor (17) during
running condition.

This invention constitutes synchronizing of these parameters which
have been developed to achieve the desired starting torque required
in service for use on 6000 HP electric locomotives for freight
application as illustrated in Fig 1.


WE CLAIM:
1. An improved higher capacity induction motor with high starting torque for
electric locomotive, hauling freight at high gradient locations, comprising:
- a stator having at least one stator core (5) formed of sheet steel
lamination, a plurality of punched slots constructed along a length of the
stator core (5), at least one stator core (5) having a stator coil (1), the
stator coil (1) is formed of a plurality of turns with each turn placed inside
one of said plurality of punched slots to form a 3 phase winding, the
supply terminals (10) projecting out of the stator windings;
- a rotor (4) having a shaft (3) including a plurality of sheet steel punching
(9) retained at both ends of the shaft (3) by multiple end plates (8), the
rotor punchings (9) accommodating several rotor bars (6); and
- a rotor suspension means (12, 18) enabling mounting of the improved
motor (17) on an existing axle, the roller suspension means (12, 18)
comprising a suspension tube (18), and a bearing (14),

characterized in that the stator coil (1) is provided with eight member of
turns, and in that the rotor bars (6) each having ends, each pair of ends is
joined via a shorting ring made of copper to form a cage-shaped motor,
and in that the length of the stator core with punched slots being 500 mm
such that the stator including the rotor is compatably operable.

ABSTRACT

TITLE: AN IMPROVED HIGHER CAPACITY INDUCTION MOTOR WITH HIGH
STARTING TORQUE FOR ELECTRIC LOCOMOTIVES, HAULING FREIGHT
AT HIGH GRADIENT LOCATIONS
An improved higher capacity induction motor with high starting torque for
electric locomotives, hauling freight at high gradient locations, comprising a
stator having at least one stator core (5) formed of sheet steel lamination, a
plurality of punched slots constructed along a length of the stator core (5), at
least one stator core (5) having a stator coil (1), the stator coil (1) is formed of a
plurality of turns with each turn placed inside one of said plurality of punched
slots to form a 3 phase winding, the supply terminals (10) projecting out of the
stator windings; a rotor (4) having a shaft (3) including a plurality of sheet steel
punching (9) retained at both ends of the shaft (3) by multiple end plates (8),
the rotor punchings (9) accommodating several rotor bars (6); and a rotor
suspension means (12, 18) enabling mounting of the improved motor (17) on an
existing axle, the roller suspension means (12,18) comprising a suspension tube
(18), and a bearing (14), characterized in that the stator coil (1) is provided with
eight member of turns, and in that the rotor bars (6) each having ends, each
pair of ends is joined via a shorting ring made of copper to form a cage-shaped
configuration of the motor such that the stator including the rotor is operably
compatible.