FIELD OF THE INVENTION
The invention relates to a 3-Phase Traction Motor with Star Connected Stator for
DEMU Application.
BACKGROUND OF THE INVENTION
Traction motors are fitted on the axle of coaches and locos engines to overhaul
the train. Basically, a traction motors has two parts static and rotating. When a
3-phase electric power is fed to these traction motors the rotating magnetic flux
is generated in static parts which produces rotating torque in the rotating part of
the machine. This rotating torque is transferred to loco wheel with gear pinion
arrangement and finally the loco accelerates. The traction motor is being used in
transportation specially in electric loco, Diesel electric locos, electrical multiple
unit (EMU) and diesel-electric multiple unit (DEMU). These traction motors has
stator coils which are housed in a stator core. When, the 3-phase supply is fed to
these traction motors a rotating magnetic field is generated in the stator core,
which rotates at a synchronous speed. For the same power application, a new 3-
phase STAR connected traction motor with low voltage and high current is
designed. This low voltage and high current is required by a control system for
controlling the coach speed.
The present invention seeks to overcome this drawback of the prior art of high
voltage and low currents requirement.

OBJECTS OF THE INVENTION :
It is therefore an object of the invention to propose a 3-phase traction motor
with STAR connected stator which produces power with low voltage and high
current suitable for EMUs and DEMUs applications.
Another object of the invention is to propose a 3-phase traction motor with STAR
connected stator which produces power with low voltage and high current
suitable for EMUs and DEMUs applications, which is enabled to increase line
current capacity including gear ratio of the traction motor.
SUMMARY OF THE INVENTION
Accordingly, there is provided a 3-phase STAR connected traction motor for EMU
and DEMUs applications, comprising: a stator core (2) formed of a single piece
low loss sheet steel laminations clamped between two cast clamping plates
rigidly fixed on a stator frame; a rotor core (1) fitted on a rotor shaft (16); the
rotor core (1) formed of the low loss high permeability sheet steel laminations
staked under pressure; a plurality of rotor bars embedded in the rotor core and
brazed with short circuit rings; and terminal box (20) with rubber gaskets and
glands with rubber seals to prevent the water entry inside the terminal box (20).
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING :
Figure 1 Shows a longitudinal sectional view of the traction motor according
to the invention.

DETAILED DESCRIPTION OF THE INVENTION :
IM3402BZ
Traction motor type IM3402BZ is specially designed considering the requirement
of IGBT based 25KV AC EMU. It is a 3-phase, 6 poles self ventilated traction
motor suitable for axle mounting on taper roller suspension bearings. It complies
with IEC-60349. In this traction motor speed and temperature sensors are
provided for getting the signals of motor RPM and core temperature of traction
motor to control the system for required performance.
Rating :
Continuous Maximum
Motor Voltage 1186 Volts 1400 Volts
Stator current 180 Amp. 225 Amp
Power 275 kW 275 kW
Motor Speed 1459 Rpm 3000 Rpm
Stator Frequency 74 Hz 138 Hz
Outstanding features of BHEL designed traction motor type
IM3402BZ are as follows:
• Machine confirms to international standard IEC-60349.
• Motor has been designed with class-200 insulation system for higher
temperature rise limits.
• Stator of motor has been VPI treated with solventless silicone resin.
• Sealed bearing are used for longer life.
• Taper roller suspension bearings arrangements are used for easy
mounting on loco axle.

DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the traction motor is designed with class 200
insulation system and is VPI treated with solventless silicon resin. The stator
punching are made from low loss high permeability sheet which are stacked and
shrink fitted in the stator housing. The stator coils are made from polyimide
covered conductors which are housed in the stator slots using polyamide slot
liners.
The rotor punching also use the low loss high permeability sheet steel. The rotor
punching are stacked on the shaft directly. The short circuit rings are induction
brazed to the rotor bars. Fans are fitted on DE and NDE ends for provision of self
ventilation.
The traction motor is provided with a terminal box and is axle hung nose
suspended in the bogie. The transmission is through a single reduction gear and
it is housed in a gear case.
STATOR FRAME :
The Stator frame is machined from a nodular iron casting and alignment of the
end shield and the bore of the stator frame is ensured. Lifting eyes are provided
on two ends of the frame.
The stator laminations (2) stamped from the silicone sheet steel, are shrink fitted
inside the frame between the two cast clamping plates.

The stator coils are made from polyimide covered copper conductor and are
further insulated using mica paper and glass insulating tapes. The coils are
assembled inside the stator slots and epoxy glass slot wedges are used for tight
fit in the slots. The coil connections are brazed; U, V & W connecting cables are
brought out and the ends are fixed to the connections on 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 sys
tern is obtained.
The terminal box is a sealed type. Rubber gaskets and glands with rubber seals
for the incoming cables are provided. This prevents the water entry inside the
terminal box.
On the non-driving end (NDE) side air-inlet chamber (13) is provided, the top of
which is connected through rubber bellows to an air duct inside the coach so that
clean air from inside the coach is available. Similarly, on the DE side, an air
outlet (11) is provided which prevents water entry, due to splashing, inside the
motor.
EARTH RETURN BRUSH :
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 axie axle by a
helical spring.

Equipment must be connected to this point. Stator frame can also be earthed by
connecting the earthing point provided at the sandwich suspension side of the
state frame to the bogie.
BEARINGS :
The rotor is supported on cylindrical roller bearings (3,4), arranged for grease
lubrication by means of a grease gun.
The rotor (1) is located axially by the NDE bearing, the DE bearing applies no
axial restraint and so permits differential expansion between the rotor (1) and
the stator frame. Each bearing outer race is a push fit into the end shield bores
and each inner race is shrink fitted on the shaft.
Inner labyrinths are provided on the end shield to prevent the lubricant
penetrating into the machine.
AXLE SUSPENSION TAPER ROLLER BEARINGS :
The taper roller bearings (5) are housed in cast steel suspension tube which is
accurately machined to centralize the bearing bores on the DE and NDE side.
The inner race of the taper bearings are shrunk fitted on the axle and
subsequently the suspension tube with taper roller bearings and end fittings are
slider 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 the lateral movement of the motor during running. The traction
motor is bolted to axle suspension tube with the help of our bolts each on DE
and NDE.

TRACTION MOTOR GEARS AND GEARCASE :
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).
The gear case (7) is of steel welded construction and is arranged to be divided in
two halves with bolts used for coupling together. Gear case is integrated as a
single piece is bolted to the motor frame and bracket. Six felts are used at the
spigot fitting part of the motor and the gear case and at the penetrating part of
the axle through the gear case.
STATOR WINDING :
STAR connection is shown in below :


In the traction motor, the stator coils are connected in STAR as shown below.
The line current carrying capacity in DELTA connection is V3 times higher than
the line current capacity in STAR connection, while the voltage across terminals
is 1/V3 times the voltage across STAR connected terminals.

WE CLAIM
1. A 3-phase STAR connected traction motor for EMU and DEMUs
applications, comprising:
a stator core (2) formed of a single piece low loss sheet steel laminations
clamped between two cast clamping plates rigidly fixed on a stator frame;
a rotor core (1) fitted on a rotor shaft (16); the rotor core (1) formed of
the low loss high permeability sheet steel laminations staked under
pressure; a plurality of rotor bars embedded in the rotor core and brazed
with short circuit rings; and
terminal box (20) with rubber gaskets and glands with rubber seals to
prevent the water entry inside the terminal box (20).
2. The motor as claimed in claim 1, wherein the insulation system of the
motor constitutes class 200 and treated with solventless silicon resin.
3. The motor as claimed in claim 1, wherein the stator coils are made from
polyamide covered conductors, and wherein the stator coils are disposed
in stator slots using slot liners.
4. The motor as claimed in claim 1 or 3, wherein the coil connections are
brazed, and wherein the end of the U, V, and W connecting cables are
connected on the terminal block.
5. The motor as claimed in claim 1, wherein the rotor is supported on
cylindrical roller bearings.

6. The motor as claimed any of the proceeding claims, wherein the pinions
driving the axle through a spur gear wheel, wherein the pinion is shrunk
on the rotor shaft, and wherein the pinion and the gear wheel are
disposed in the gear case.
7. The motor as claimed in claim 1, wherein the current carrying capacity
and the voltage across the terminal are V3-times and 1/√3 times of that of
delta connected stator.
8. The motor as claimed in claim 1, which has a rating of 275kW, 1186V,
180A, 1459RPM.

The invention relates to a 3-phase STAR connected traction motor for EMU and
DEMUs applications, comprising: a stator core (2) formed of a single piece low
loss sheet steel laminations clamped between two cast clamping plates rigidly
fixed on a stator frame; a rotor core (1) fitted on a rotor shaft (16); the rotor
core (1) formed of the low loss high permeability sheet steel laminations staked
under pressure; a plurality of rotor bars embedded in the rotor core and brazed
with short circuit rings; and terminal box (20) with rubber gaskets and glands
with rubber seals to prevent the water entry inside the terminal box (20).