FIELD OF THE INVENTION
The present invention relates to the field of traction applications and specifically
3-phase traction motor for electrical multiple unit (EMU) applications.
BACKGROUND OF THE INVENTION
Previously, DC series traction motors were frequently being used in the fields of
electric locomotives, diesel locomotives, EMUs, DEMUs and MEMUs. These DC
machines develop high starting torque, which is required for traction applications
and control of DC traction motors are also easy but the most disadvantages with
these DC traction motors is presence of carbon brushes and communications
which are used to make electrical contacts with rotating part.
After invention of solid state devices like, diodes, GTO, IGBTs etc now control of
3-phase induction motors is very easy and user friendly. Hence, with the
development of modern control philosophy, now a days, 3-phase induction
motors are taking place in traction applications.
When these 3-phase traction motors are designed to run in Mumbai suburban
where there is a lot of rush during peak hours and where vibrations are very
severe and there are many cases of stator coil failure due to high vibration in
motors presently running in these areas. These areas are also flooded in rainy
season and many cases observed for failure due to ingress of water inside motor.
In view of above considering natural constraints, a new 3-phase traction motor
has been designed with flood proofing and support arrangement of stator coil
overhang portion to absorb high vibration.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a water-proof 3-phase
traction motor for electrical multiple units which allows electric locomotives to
run in flooded areas at a certain level and speed.
Another object of the invention is to propose a water-proof 3-phase traction
motor for electrical multiple units which is provided with support arrangement for
overhand of stator coils to reduce frequent failure of stator coils due to presence
of excessive vibration in series.
SUMMARY OF THE INVENTION
According to the invention, there is provided a 3-phase water-proof traction
motor suitable for IGBT based 25kV AC EMU to allow the EMU coaches to run
through flooded track.
The traction motor is a 3-phase, 4-poles traction motor with ventilators on both
DE and NDE side for self-cooling of the machine during service. This machine is
suitable for axle mounting on taper roller suspension bearings on the axles of
the bogies at both ends for smooth and easy mountings. The machine has a
terminal box and earth return assembly. For monitoring and control of the EMU
and performance of the associated devices like speed sensor as well as
temperature sensors are provided to capture the machine parameters. This
machine is provided with a support arrangement for stator coils as well as flood
proof arrangement.
SPECIAL FEATURES
Outstanding features of this inventive traction motor are as follows:
• Machine confirms to IEC 60349-2.
• Suitable for high vibration levels.
• High permeability, low loss stator and rotor laminations are used.
• Silicon based Class-200 insulation system.
• VPI treated with solventless silicone resin.
• Sealed bearings arrangement for low maintenance.
• Taper roller suspension bearing arrangement to make user friendly.
• Casted frames are used for which pattern is designed with 3D model.
• Support Arrangement to overhang of stator coils.
• Speed sensor and temperature sensor provided for getting signals for
control applications.
• Earth return assembly provided for earthing of primary of transformer.
• Corona resistance copper used in stator coils for better performance.
• 3-phase terminals are provided on terminal box.
• Ventilators are provided at both ends for self-cooling of motor during
service.
• Wire locking of end shield bolts and air inlet bolts are done for proper
locking during service.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG.1: Shows a longitudinal sectional view of the traction motor
according to the invention.
FIG.2: Shows a comparison of the inventive stator Overhand arrangement
in respect of prior art.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT:
According to the invention, the traction motor is constructed with class-200
insulation system and VPI treated with solventless silicone resin. The stator
laminations (2) are made from low loss high permeability sheet steel which are
stacked together with end laminations and clamp rings at both ends to form a
complete stator core. This stator core is shrink fitted in a stator housing (12).
Stator housing (12) is machined from Spheroidal or Nodular Graphite Iron
Castings. Alignment of end shield and the bore of the stator frame is carefully
made. Lifting eyes are provided on two ends of the frame.
A plurality of stator coils (18) made from corona resistant copper conductor, are
insulated using mica paper and glass insulating tapes. The coils are assembled
inside corresponding number of stator slots and tightly fitted with at least
equivalent number of epoxy slot wedge. The coil connections are brazed, and R,
Y & B connecting cables are bought out and the ends are fixed to a terminal
block. The terminal block is housed in a light weight terminal box assembled on
the top of the stator frame.
Before making the connections in the terminal box, the complete stator is VPI
treated with solventless silicone resin so that void free, compact insulation
system is obtained.
The rotor laminations (1) are also made from low loss high permeability sheet
steel and stacked together on the rotor shaft (16) by rotor clamp rings to form
the rotor core. The rotor bars are then inserted in the slots of the rotor core and
induction brazed to short circuit rings to make a complete squirrel cage rotor.
Ventilators (14 and 17) are fitted on both DE and NDE side for provision of self-
cooling of the motor during operations.
The terminal box (20) provided to the traction motor is a sealed type box, in
which rubber gaskets and glands with rubber seals for the incoming cables are
provided. The motor is axle hung nose suspended in a bogie with axle
suspension taper roller bearings (5) at both ends. The transmission of power
from the motor to the axle is through a single reduction gear (6) which is housed
in a gear case (7).
On the NDE side, an air-inlet chamber (13) is provided, the top of which is
connected through a leather bellows, to an air duct inside the bogie so that clean
air from inside the boogie is available. Similarly, on the DE side, an air outlet (11)
is provided which prevents water entry, due to splashing, inside the motor.
The rotor is supported on cylindrical roller bearing (3 and 4) at both ends and
grease lubrication by means of a grease gun is arranged through grease nipple
for periodic regreasing of the bearings without dismantling. Each bearing outer
race is push fit into the end shield bores and each inner race is shrunk fitted on
the rotor shaft. Inner labyrinths are provided on the end shield to prevent the
lubricant penetrating into the machine.
The taper roller bearings (5) are housed in a cast steel suspension tube
accurately machined to centralize the bearing bores on the DE and NDE side.
The inner race of the taper roller bearings (5) are shrunk fitted on the axle and
subsequently the suspension tube with the taper roller bearings and end fittings
are slided over the axle. Grease nipples are provided at both the ends to
lubricate the bearings periodically. The lateral clearance available between the
two taper bearings restricts any lateral movement of the motor during operation.
The traction motor is bolted to axle suspension tube with the help of four bolts
each on DE and NDE.
The motor pinion drives the axle through a spur gear wheel (6) which is pressed
on the axle. The pinion (8) is shrunk on a tapered extension of the rotor shaft.
Pinion and gear wheel are provided in the gear case (7).
Gear case (7) is of steel welded construction and is divided in two halves with
bolts for coupling together. Gear case (7) is integrated as a single piece and
bolted to the motor frame and bracket. Also six felts are used at the spigot fitting
part of the motor and gear case and at a penetrating part of the axle through
gear case.
A copper graphite earth return brush is fitted to the motor to make contact with
the axle and provide a low resistance path for earth return. This brush is
contained in a bronze casting holder and is pressed against the axle by a helical
spring.
The stator frame can be earthed by connecting the earthing point provided at
the sandwich suspension side of the state frame to the bogie.
WE CLAIM:
1. An improved three-phase water-proof traction motor for adaptation in
railway locomotives to allow operation through flooded tracks, the
motor having a single parallel path, the improvement is characterized
by comprising:
- a terminal box (20) with rubber gaskets and glands with rubber seals
to prevent water entry inside the terminal box (20);
- stator housing made of spherodial or modular graphite iron casting
with stator core formed of low-loss high permeability sheet steel;
- a plurality of rotor bars of trapezoidal cross section, inserted in each
slot of rotor core and brazed together at both the ends with short
circuit rings;
- a plurality of stator coils made from corona-resistant copper
conductors insulated with mica paper and glass insulating tapes and
fitted to the stator slots with epoxy wedges;
- DE and NDE end shields bolted to stator housing at both the ends; and
provided with ventilation means for self-cooling of the motor;
- cylindrical roller bearing at both ends are grease lubricated and
provided with labyrinths to prevent contamination of grease by dirt
and moisture; and
- a winding support arrangement for the overhung portion of the stator
coil to avoid damage during operation.
2. The motor as claimed in claim 1, wherein the rotor laminations are
made from low-loss high permeability sheet steel.
3. The motor as claimed in claim or 2, wherein an inlet air chamber and
an outlet is provided respectively on the NDE and DE sides.
4. The motor as claimed in claim 1, wherein the roller bearings are
housed in a cast-steel suspension tube.
5. The motor as claimed in claim 1, wherein the power from the motor to
the axle of the locomotive is transferred through a single reduction
gear housed in a splitted gear casing.

ABSTRACT

The invention relates to an improved three-phase water-proof traction motor for adaptation in railway locomotives to allow operation through
flooded tracks, the motor having a single parallel path, the improvement is characterized by comprising: a terminal box (20) with rubber gaskets and glands with rubber seals to prevent water entry inside the terminal box (20); stator housing made of spherodial or modular graphite iron casting with stator core formed of low-loss high permeability sheet steel; a plurality of rotor bars of trapezoidal cross section, inserted in each slot of rotor core and brazed together at both the ends with short circuit rings; a plurality of stator coils made from corona-resistant copper conductors insulated with mica paper and glass insulating tapes and fitted to the stator slots with epoxy wedges; DE and NDE end shields bolted to stator housing at both the ends; and provided with ventilation means for self-cooling of the motor; roller bearings at the driving end and ball bearing at
the non-driving end are grease lubricated and provided with labyrinths to prevent contamination of grease by dirt and moisture; and a winding support arrangement for the overhung portion of the stator coil to avoid
damage during operation.