FIELD OF INVENTION
The present invention generally relates to the field of high power metro and DC-
EMUs for traction application. More particularly, the invention relates to the
inductive shunt device used in weak fielding circuit of traction motors.
BACKGROUND OF INVENTION
Traction motors used for metro and EMU applications are often subjected to
transients due to voltage fluctuations. However, the motor design is such that
the field inductance is usually high enough to suppress these transients. But
during field-weakening when maximum flux distortion occurs, if the field current
is diverted with a resistive shunt these transients tend to follow the path of least
resistance through this resistive shunt, thereby accentuating traction motor
flashovers. In order to avoid such conditions, the field of traction motors used in
metro and EMUs is normally diverted through an INDUCTIVE SHUNT, inductance
of which has been matched suitably with inductance of Traction Motor.
Prior art 93 kW DC traction motor used for metro and EMU applications was
recently replaced with 167 kW DC traction motor to cater for increased loading
level and high speed requirement. To be precise, the prior art traction motors of
rating 338V, 310A,93 kW has been replaced by new traction motor having rating
675V,275A,167 kW. For the 167 kW DC - traction motors corresponding type of
inductive shunt is required to be developed.
Constructional features of prior art inductive shunt:
(1) As shown in figure-2, the prior art Inductive Shunt consists of a laminated
core (15) formed with two T-shaped halves butted together forming an
H-Shaped when assembled. The laminations are clamped together with
Insulated rivets and held in between four number flanged endplates (16)
by Insulated studs (17).
(2) The Prior art Inductive Shunt has two numbers of copper coils (18,19).
Each coil (18,19) has two sections wound on a flat similar to that of the
main pole coil of the traction motor. The coils (18, 19) are insulated with
class H insulating materials.
(3) The coils (18,19) are held separately and in position on the core by
means of a coil spacer (20). Coil insulating washers (21, 22) are provided
for additional insulation between the core (15) and coil (18,19).
(4) The two coils (18,19) are permanently connected in parallel and the
outgoing cables (23,24) are connected up to terminals (25,26) arranged
on two rods insulated with moulded bakelite paper and secured to one of
the endplates.
(5) Four fixing holes are provided at the end plates (16) for under slung
mounting arrangement.
(6) Separately mounted perforated protective cover is provided to protect the
coils against foreign particles.
OBJECT OF INVENTION:
The object of the invention is to propose an Inductive Shunt device for field
weakening circuit of traction motor for high power metro and EMU applications.
SUMMARY OF INVENTION
According to the invention, an improved inductive shunt has been developed for
the high power traction motor. The inductive shunt is configured to be suitable
for increased capacity of the motor so as to suppress the transients generated
during weak fielding at higher voltage. Inductance of the inventive inductive
Shunt has been designed in corresponding with the inductance of the high power
traction motor.
The inductive Shunt is designed with a class-200 insulation system with higher
temperature rise limits. The class 200 insulation system is designed with
Polyamide Tape, PTFE Tape, Silicone treated Woven Glass Tape, silicon asbestos
putty. The inductive Shunt coil is VPIed in class 200 Solvent less polyesterimide
varnish.
The inventive device comprises four sections in laminated magnetic core, air gap
between core sections and two numbers flat wound copper coils. The inductive
shunt coils are wound with class 200 insulation system and are VPIed in class
200 polyesterimide varnish. The outgoing terminals of two coils are permanently
connected in parallel.
RATING:
Continuous DC current Rating : 130Amps

Essential features:
¦ Class - 200 insulation on the coils
¦ VPI of the coils with class 200 Solvent less polyesterimide varnish.
¦ Sections of the magnetic core are built up from steel laminations riveted
together.
¦ Inductive shunt is configured for under slung mounting arrangement.
¦ A Protective cover is mounted on shunt body itself to protect against
foreign particles.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 : Shows an improved Inductive Shunt device according to the
invention.
Figure 2 : shows an assembly of Inductive Shunt according to the prior
art a coil insulation system of the inventive inductive shunt
device.
Figure 3A: shows a coil insulation system of the prior art inductive
shunt arrangement.
Figure 3B : shows a coil insulation system of new inductive shunt
device.
Table 1 - shows comparison between new inventive shunt device and
prior art arrangement of inductive shunt.
DETAILED DESCRIPTION OF THE REFERRED EMBODIMENT:
(1) As shown in figure -1, the Inductive Shunt consists of four sections
(l,2,3,and 4) constituting the magnetic core. Each core section is built up
from steel laminations riveted together.
(2) The Inductive Shunt has two numbers of copper coils (5,6). Each coil has six
sections, wound on a flat similar to that of the main pole coil of the traction
motor. The coils (5,6) are insulated with class 200 insulating materials.
(3) Said two coils (5,6) of the shunt are wound on two separate core sections
(1,3), and in between each side of these sections (1,3), another two core
sections (2,4) are clamped with four U - pieces (7,8,9 and 10) so as to
complete the magnetic circuit through air gap.
(4) Said two coils (5,6) of the Inductive Shunt are permanently connected in
parallel. For making connections, the outgoing cables are taken out from
two terminals (11 and 12). Epoxy cable cleat (13) is provided to support the
outgoing cables.
(5) Four holes are provided at each of top U-pieces (7,8), for under slung
mounting arrangement.
(6) A two-piece perforated steel protective cover (14) is mounted on the U-
pieces (7,8,9,10) to protect the coils (5,6) against foreign particles.
INSULATION SCHEME:
The insulating properties and strength of the insulating materials are considered
to avoid breakdown due to excessive voltage gradients set up in the machines.
The life of the machine merely depends upon the life of selected insulation. The
excessive temperature rise may cause insulation failure within very short period
of application. If the motor is continuously operated above the specified
temperature limit, life of the insulation and hence life of the machine will be
reduced from its standard designed life. By providing proper ventilation and
cooling, the temperature rise can be kept within the safe limit. With this view the
inventive Inductive shunt device for high power metro and DC EMU application
has been designed with class-200 insulation system.
As shown in Figure-3B, for insulation of the inductive shunt coil Polyamide
Tape (27) is used as the inter turn insulation. Each section of coils (5,6) is
separated by polyamide washers (28). Then the complete coil (5,6) is wound
with a Silicone treated Woven Glass Tape (29) and the Polyamide Tape (27).
PTFE tape pieces (30) are used for protection at the corners of the coil (5,6).
Silicone Asbestos Putty (not shown) is used to level the gaps between the coil
sections. VPI of inductive shunt coils (5,6) is carried out in class-200 FT2005
Polyesterimide Varnish. In prior art, a moisture resistant class-H varnish was
used for VPI of the coils.
WE CLAIM
1. An improved inductive Shunt device for high power traction motor,
comprising of four sections forming a magnetic core of steel laminations
riveted together, air gap between the core sections, two number of
copper coils each having six sections and U - pieces to clamp the core
sections together.
2. The Inductive Shunt device as claimed in claim 1, wherein, the device is
enabled to maintain a continuous current rating of 130A and inductance of
65mH at 50 Hz AC.
3. The Inductive Shunt device as claimed in claim 1, wherein the device is
capable to limit temperature rise IEC 349 - 20 deg Celsius.
4. The Inductive Shunt device as claimed in claim 1, wherein both the coils
are permanently connected in parallel.
5. The Inductive Shunt device as claimed in claim 1, wherein said class 200
insulation system comprises of polyamide tape acting as inter turn
insulation, polyamide washers separating each section of the coils,
polyamide tape covering the coil ,PTFE tape protection pieces at corners
and silicon treated woven glass tape covering the complete coil.
6. The Inductive Shunt device as claimed in claim 1, wherein the device is
adaptable for under slung mounting conditions.
7. An improved inductive Shunt device for high power traction motor, as
substantially described and illustrated herein with reference to the
accompanying drawings.

The present invention relates to an improved inductive Shunt device for high
power traction motor, comprising of four sections forming a magnetic core of
steel laminations riveted together, air gap between the core sections, two
number of copper coils each having six sections and U - pieces to clamp the core
sections together.