FIELD OF INVENTION
The present invention generally relates to a D.C. traction motor for high powered metro or
EMU application in railways. The loading in such area of public transport system has
increased substantially along with requirement of higher speed. Accordingly the traction
drives are required to adapt to new demands of load and speed. But there are constraints
of space. The frame size of the motors should be such that they are compact and
compatible to broad gauge, high powered underground railway and D.C. EMU application.
It specifically relates to a D.C. motor with a special insulation system and suspension
bearing arrangement which successfully meets the demands of increased load and higher
speed within the limits of space restriction and rise of temperature.
BACKGROUND OF THE INVENTION
At present 93 kW DC traction motor is manufactured for metro and DC EMU application.
However, due to increased loading level and high speed requirement, there is a need for a
suitable motor with higher rating and high reliability.
In prior art the magnet frame (item 01 of figure 2) is made of high permeability steel and
is machined to ensure alignment of the end shields (item 02 and 03 of figure 2), main
poles, compoles and axle ways.
The armature core (item 06 of figure 2) is built from sheet steel laminations assembled on
the shaft (item 07 of figure 2). The laminations are held together between endplates (item
08 and 09 of figure 2) and are fitted on the shaft. The armature is lap wound and armature
conductors are insulated with Class-H Insulation system.

Epoxy slot wedges (item 11 of figure 2) are used to hold the coils (item 10 of figure 2) in
slots and Res-1-glass bands (item 12 of figure 2) retain in the end portions of the coils. The
wound armature is finally vacuum pressure impregnated in moisture resistant class H
varnish.
The armature is supported on two grease lubricated roller bearings (item 04 and 05 of
figure 2). The bearing assemblies are of sealed type provided with adequate labyrinths.
The commutator (item 13 of figure 2) is of arch bound construction. The copper segments
are made from hard drawn silver bearing copper (item 14 of figure 2) and risers integral
with segments are slotted to receive the armature coil leads. The armature coil leads are
finally TIG welded to commutator risers (item 15 of figure 2).
The copper segments are insulated from each other with the mica segments and are held
together with the Steel V rings (item 16 of figure 2), insulated with the molded micanite
V-rings. PTFE bush (item 17 of figure 2) is used on exposed surface of the commutator
front micanite V-ring to obtain high creepage.
The main poles (item 18 of figure 2) are built up from steel lamination riveted together.
The main field coils (item 19 of figure 2) are made of copper strap wound on flat, whereas
the compole (item 20 of figure 2) coils (item 21 of figure 2) are edge wound. The coils are
insulated with Class-H insulating materials. Pole and coils assembly together is vacuum
pressure impregnated in moisture resistant class H varnish.
There are four brush arms, each carrying a brush holder (item 22 of figure 2) with to
carbon brushes (item 23 of figure 2). Twin-stud insulators secure brush holders.

The pinion (25) has a taper ground bore and its shrink-fitted on to the armature shaft
(07). The gear (26) is mounted directly on the locomotive axle. The gear (26) is mounted
directly on the locomotive axle. The gears are enclosed in a gear case (24) mounted on the

motor which is made in two halves bolted together.
Axle bearing are sleeve type bearing (item 27 and 28 of figure 2) made in two halves from
bronze castings and are lined with babbit metal at the load bearing surfaces. The bearings
are oil lubricated by worsted wool felt.
For increased loading and high speed requirement in metro and EMU trains, 167 kW
traction motor has been developed. One traction motor is fitted on one axle of the bogie
which has four axles. The power supply may be at 750V DC or 1500V DC depending upon
the combinations of motors used to propel the train. Novel features with respect to the
prior art have been added to the traction motor of subject invention as given here under:-
In armature coil insulation of new traction motor silicone bonded mica paper tape with
polyimide backing is used to make the insulation class-200 and polyimide tape is lapped
around the conductor after silicone treated woven glass tape to provide extra mechanical
strength. Previously in armature coil insulation polyimide tape was used as a base
insulation and after that PTFE tape, epoxy bonded mica paper tape and woven glass tape
was lapped around the conductor. Hence new traction motor has better temperature rise
limit of armature and hence machine can be used for higher rating applications.
In main field coil insulation of new traction motor, conductors are wounded with polyamide
tape, silicone bonded glass baked mica paper tape and silicone treated woven glass tape.
At corners of conductor Glass Mica Glass is used to increase the mechanical strength.

In between upper and lower part of coil Silicone Asbestos Putty is applied. Previously in
main field coil insulation, conductors were wounded with Woven Glass Tape, Epoxy bonded
Glass Mica Tape and Woven Glass Tape. Polyamide Washers were used at outer surface of
coil and in between two layers. Hence new traction motor has better temperature rise limit
of main field coils and hence machine can be used for higher rating applications.
In compole coil insulation of new traction motor Polyamide washer is used as interturn
insulation. End turns of coil are insulated with Polyimide Tape and Glass Mica washers at
out side. The coil is lapped with Silicone bonded Glass baked Mica Paper Tape and Silicone
treated Woven Glass Tape. Glass Mica Washers and Epoxy Washers are used at outer
surface of coil. Previously in Compole coil insulation Polyamide washer was used as
interturn insulation. The coil was lapped with Woven Glass Tape and Epoxy bonded Glass
Mica Tape. Polyamide Washer was used at outer surface of coil. Hence new traction motor
has better temperature rise limit of compole coils and hence machine can be used for
higher rating applications.
Armature, main field coils and compole coils of new traction motor are vacuum pressure
impregnated in class-200 FT2005 Polyesterimide Varnish while armature, main field coils
and compole coils of prior art were vacuum pressure impregnated in moisture resistant
class H varnish. Hence new traction motor has better temperature rise limit of armature,
main field coils and compole coils and hence machine can be used for higher rating
applications.
Continuous rating of new traction motor is 675 V, 275 A, 1035 RPM, 167 kW while earlier
traction motor had continuous rating of 338 V, 310 A, 1070 RPM, 93 kW. Hence due to
increased power new traction motor can operate in higher traffic density with higher speed.

Power to weight ratio for new traction motor is 0.08 while for earlier traction motor Power
to weight ratio as, 0.06. Existing fully worn wheel diameter of Kolkata Metro system is 780
mm. Due to higher Power to weight ratio of new traction motor its size becomes smaller
for higher rating and new motor can be accommodated in the existing bogie of Kolkata
metro having fully worn wheel diameter of 780 mm.
In new traction motor Taper roller suspension bearing arrangement is being used while in
earlier traction motor sleeve type journal bearings were used. Taper roller suspension
bearing arrangement requires less maintenance and hence availability of metro trains with
new traction motor will be higher.
In new traction motor axle bearings are grease lubricated while axle bearings of earlier
traction motor were oil lubricated. Hence new traction motor has longer relubrication
period compared to earlier traction motor.
The main object of the invention is to provide traction motor With higher rating and higher
speed for high power Metro and EMU application but compact in size having high power to
weight ratio.
Another object of the invention is to provide- a machine with class-200 insulation system
with high temperature rise limits during application resulting higher load bearing capacity.
A further object of the invention is to provide a machine with taper roller suspension
bearing arrangement instead of sleeve type journal bearings used in prior art.

SUMMARY OF INVENTION:
To meet the increased fbading conditions and higher speed of metro and EMU applications
167 kW traction motor has been designed in place of 93 kW traction motor presently being
used for same application.
New motor is designed with class-200 insulation system in armature coil insulation, main
field coil insulation, compole coil insulation having higher power to weight ratio. Due to
higher Power to weight ratio of new traction motor its size becomes smaller for higher
rating and new motor can be accommodated in the existing bogie of Kolkata metro having
fully worn wheel diameter of 780 mm. New motor is designed with class-200 insulation
system with high temperature limits. The class 200 insulation scheme is designed for this
machine with Polyimide Tape PTFE Tape, Silicone bonded Mica paper Tape with Polyimide
backing, Silicone treated Woven Glass Tape and Polyimide Washer. The new motor has
also been designed with taper roller suspension bearing arrangement.
ACCOMPAYING DRAWINGS:
Figure 1: shows the long section of new traction motor according to the invention.
Figure 2: shows the long section of earlier traction motor.
Figure 3: shows the comparison of armature coil insulation scheme between earlier and
new traction motor.

Figure 4: shows the comparison of main pole coil insulation scheme between earlier and
new traction motor.
Figure 5: shows the comparison of compole coil insulation scheme between earlier and new
traction motor.
DETAILS DESCRIPTION OF PREFERRED EMBODIMENT
The invention will now be described in an exemplary embodiment as depicted in the
accompanying drawing. There can however be other embodiments of the same invention,
all of which are deemed covered by this description.
It is a DC series motor wound with "class-200" insulation system, four pole, and self
ventilated traction motor suitable for axle mounting on taper roller suspension bearings. It
is supported on the nose by a resilient suspension unit. The traction motor of the invention
is an especially designed motor for DC line fed, broad gauge, high power underground
railway and DC EMU application. It complies with IEC-60349: 2001/ IEEE-11: 1982.
Rating:
Continuous Rating: 675V, 275A, 1035 RPM, 167 KW, 100% FF
One Hour Rating: 675V, 310A, 995 RPM, 187 KW, 100% FF
Gear Ratio: 16/69
Type of Cooling: Self cooling
Class of insulation: Class 200

Motor efficiency at rated power: 90.1% at continuous rating.
Type of suspension; Nose suspended Axle mounted with taper roller suspension

bearings.
Weight of fraction motor; With pinion, gear wheel and gear case - 2387 Kg (Approx.)
Only motor including pinion - 2069 Kg (Approx.)
Temperature rise of winding; as per IEC 60349 norms
Outstanding features:
• Machine conforms to IEC 349.
• Class-200 insulation on Armature coils and field coils (Fig. 3,4, 5).
• Sealed armature bearings.
• Taper Roller suspension bearing arrangement.
• TIG welded armature.
• PTFE brush protection on commutator front vee ring.
• VPI of armature with Solventless polyester varnish.
• High permeability steel magnet frame.
• Armature core is built from electrical grade sheet steel laminations.
• Commutator is of Arch Bound construction.
• The poles are built up from steel laminations riveted together.
• A terminal box is provided to facilitate the cable connections.

• The pinion has a taper ground bore and is shrink fitted onto the tapered armature
shaft of matching profile.
• The armature is supported on two grease lubricated roller bearings. The bearing
assemblies are of sealed type provided with adequate labyrinths.
Insulation scheme:
The insulating properties and the strength of the insulating materials are considered on
account of breakdown due to excessive voltage gradients set up in the machine. The life of
the machine merely depends upon the life of the insulation. The excessive temperature rise
may cause insulation failure within very short period of application. If the machine is
continuously operated above the specified temperature limit, the life of the insulation and
hence the life of the machine will get reduced from its normal life. By providing proper
ventilation and cooling, the temperature rise can be kept within the safe limit. With this
view new traction motor for high power metro and EMU applications has been designed
with class-200 insulation system.
In armature coil insulation (Figure 3), polyimide tape (30) is used as a base insulation and
after that PTFE Tape (40), Silicone bonded Mica paper tape (32) with polyimide backing,
silicone treated Woven Glass Tape (31) and Polyimide Tape (30) is lapped around the
conductor. In prior art Epoxy bonded Glass Mica Tape and Woven Glass Tape were used to
wound the coil.
As illustrated in Figure 4 main field coil conductors are separated by polyimide Tape (30)
and each section is lapped with Silicone treated Woven Glass Tape (31) individually on
three sides (other than lead end).

Then complete coil is wounded with polyamide tape (30), silicone bonded glass baked Mica
Paper Tape (32) and Silicone treated Woven Glass Tape (31). First and second turns of
each section is reinforced with Silicone bonded Glass baked Micanite (36).
At corners of conductor Mica Glass (37) is used to increase the strength of the insulation.
In between upper and lower part of coil Silicone Asbestos Putty (35) is used. In prior art
Woven Glass Tape and Epoxy bonded Glass Mica Tape were used to wound the coil.
In compole coil (Figure 5) Polyamide washer (43) is used as interturn insulation. End turns
of coil are insulated with Polyamide Tape and Glass Mica washers (37) at out side. The coil
is lapped with Silicone bonded Glass baked Mica Paper Tape (34) and Silicone treated
Woven Glass Tape (41). Glass Mica Washers (37) and Epoxy Washers (38) are used at
outer surface of coil. In prior art Woven Glass Tape and Epoxy bonded Glass Tape were
used to wound the coil.
VPI of armature, main field coils and compole coils are carried out in class-200 FT 2005
Polyesten'mide Varnish. In prior art moisture resistant class-H varnish was used for VPI
(Vacuum Pressure Impregnation) of the coils.
In the present invention the high permeability steel frame (item 01 of fig. 1) is machined to
ensure alignment of the end shields, magnet frame pole bores and axle ways. The nose of
the motor is resiliency supported in the bogie.
The end shields (item 02 and 03 of fig. 1) are spigoted into magnet frame with slight
interference fit and held position by means of bolts which are suitably locked.

This method of mounting ensures that the fit between the end shields and the frame
remains tight in service. Roller bearings (item 04 and 05 of fig. 1) are provided and
labyrinths are formed to prevent the escape of lubricating grease or the entry of dirt or

moisture.
The armature core (item 06 of fig. 1) is built from electrical quality sheet steel laminations
insulated from each other and assembled on the shaft (item 07 of fig. 1) with interference
fit and consolidated under pressure. The laminations are held together between endplates
(item 08 and 09 of fig. 1). Fitted on the shaft machined from nickel-chromium-
molybdenum steel.
The armature is wave wound. The armature conductors are insulated with Class-200
Insulation system. The coils (item 10 of fig. 1) are held down in the core slots with epoxy
slot wedges (item 11 of fig. 1) and Res-i-glass bands (item 12 of fig. 1) retain in the end
portions of the coils. The wound armature is finally vacuum pressure impregnated in
solvent-less polyesterimide varnish.
The armature bearing (item 04 and 05 of fig. 1) assemblies are of sealed type provided
with adequate labyrinths to avoid the contamination of the lubricating grease with dirt,
moisture cardium compound.
The commutator (item 13 of fig. 1) is of arch bound construction. The copper segments are
made from hard drawn silver bearing copper (item 14 of fig. 1) and risers integral with
segments are slotted to receive the armature coil leads. The armature coil leads are finally
TIG welded to commutator risers (item 15 of fig. 1).

The copper segments which are insulated from each other with the micanite segments, are
held together with the Steel V rings (item 16 of fig. 1), insulated with the molded micanite
V-rings. The exposed surface of the commutator front micanite V-ring is covered with PTFE
bush (item 17 of fig. 1) to obtain high creepage. Replaceable arcing horns are provided to
minimize the damage to the commutator and brush gear in the event of any flashover.
The main poles (item 18 of fig. 1) are built up from steel lamination riveted together. The
main field coils (item 19 of fig. 1) are made of copper strap wound on flat, whereas the
compole (item 20 of fig. 1) coils (item 21 of fig. 1) are edge wound. The coils are insulated
with Class-200 insulating materials. Pole and Coils assembly together is vacuum pressure
impregnated and encapsulated in solventless polyesterimide varnish.
There are four brush arms, each carrying a brush holder (item 22 of fig. 1) with two carbon
brushes (item 23 of fig. 1). Twin-stud insulators secure brush holders. PTFE bushes are
provided on each insulator pin in between two portions and the brush holder provides a
creepage surface for ease in cleaning.
The transmission to the bogie axle consists of a single reduction gear unit, the pinion (25)
of which is shrink-fit on to the motor armature shaft (07) and the gear (26) is mounted
directly on the locomotive axle.
The gear is housed in a gear case (24) mounted on the motor which is made in two halves
bolted together. The joint between the halves has an overlap and felt wipers are also
provided to prevent contamination of the gear lubricant with dirt or moisture.

Axle is supported on an axle suspension-bearing unit consisting of taper roller bearing at
the ends housed in a tube, which is bolted to the traction motor magnet frame, which
require less maintenance during service.

WE CLAIM:
1. A D.C. series traction motor for high power Metro/EMU application mainly
comprising (fig. 1):-
• steel magnet frame (01)
• end shields (02, 03)
• armature core (06)
• armature coil (10)
• armature shaft (07)
• main pole (18)
• main field coil (19)
• compole (20)
• compole coil (21)
• commutator (13)
• commutator bar (14)
• commutator rise (15)
• commutator steel V ring (16)
• PTFE bush(17)
• brush holder (22)
• carbon brush (23)
• gear case (24)
• pinion (25)
• gear (26)

Characterized in that armature coils, main field coils and compole coil are insulated
with class-200 insulation system and axle is supported by taper roller suspension
bearings (27, 28).
2. A D.C. traction motor as claimed in claim 1, wherein it has continuous rating of 167
kW, 675 V, 275 A, 1035 rpm.
3. A D.C. traction motor as claimed in claim 1, wherein the magnet frame (01) is of
high permeability steel suitably machined to ensure alignment of the end shields
(02, 03), main poles, compoles and axle ways and having the nose of the motor
resiliently supported in the bogie.
4. The end shields (02, 03) are spigotted into magnet frame (01) with slight
interference fit and are held in position by means of bolts which are suitably locked.
5. The D.C. traction motor as claimed in claim 1, wherein roller (04, 05) bearing are
provided in the armature assembly.
6. The armature assembly as claimed in claim 5 is of sealed type provided with
adequate labyrinths.
7. The D.C. traction motor as claimed in claim 1 wherein a armature coil (06) is built
from electrical quality sheet steel laminations insulated from each other and
assembled on the shaft (07) with interference fit and consolidated under pressure
and the laminations are held together between end plates (08, 09) fitted on the
shaft machined from nickel-chromium-molybdenum steel.

8. The D.C. traction motor as claimed in claim 1, wherein armature has wave wound
coils (10) which are held down on the core slots with epoxy slot wedges and with
Res-i-glass band at overhang portion.
9. A D.C. traction motor as claimed in claim 1, wherein armature coil insulation
polyimide tape (30) is used as a base insulation and after that PTFE Tape (40),
Silicone bonded Mica paper tape with polyimide backing (32), silicone treated Woven
Glass Tape (31) and Polyimide Tape is lapped around the conductor.
10. The D.C. traction motor as claimed in claim 1 wherein main field coil conductors are
separated by polyimide Tape (30) and each section is lapped with Silicone treated
Woven Glass Tape (37) individually on three sides (other than lead end). Then
complete coil is wounded with polyamide tape (30), silicone bonded glass baked
Mica Paper Tape (34) and Silicone treated Woven Glass Tape (31). First and second
turns of each section is reinforced with Silicone bonded Glass baked Micanite (36).
At corners of conductor Mica Glass (37) is used to increase the strength of the
insulation. In between upper and lower part of coil Silicone Asbestos Putty (35) is
used.
11.The D.C. traction motor as claimed fn claim 1, wherein the compole coils (21)
Polyamide washer (43) is used as inter turn insulation. End turns of coil are
insulated with Polyamide Tape and Glass mica washers (37) at outside. The coil is
lapped with Silicone bonded Glass baked mica paper tape (34) and Silicone treated
woven glass tape (41). Glass Mica Washers (37) and Epoxy Washers (38) are used
at outer surface of coil.

12. The D.C. traction motor as claimed in claim 1, wherein the armature coil (10), main
field (19) and compole coil (21) are treated with class-200 FT 2005 polyesterimide
varnish.
13. The D.C. traction motor as claimed in claim 1 wherein main poles (18) are built from
steel lamination riveted together and the main field coils are made of copper strap
wound on flat and the compole coils are edge wound.
14. The main field coils (19) and the compole coils (21) as claimed in claim 12 are
insulated with class-200 insulating materials.
15.The main pole (18) and main field coil (19) as claimed in claim 12 and 13 are
together vacuum pressure impregnated and encapsulated in polyesterimide varnish.
16. The compole (20) and compole coil (21) as claimed in claim 12 and 13 are together
vacuum pressure impregnated and encapsulated in polyesterimide varnish.
17. A D.C. traction motor as claimed in claim 1, wherein the commutator (13) is of arch
bound construction having its copper segments (14) made from hard drawn silver
bearing copper and risers (15) integral with segments are slotted to receive the
armature coil leads which are finally TIG welded to commutator riser.
18. The copper segments of the commutator as claimed in claim 15, are held together
with steel V rings (16) insulated with molded micanite V-rings, the exposed surface
of the commutator micanite V rings being covered with PTFE bush (17).

19. A D.C. traction motor as claimed in claim 1, wherein four brush arms, each carrying
a brush holder (22) with two carbon brushes (23) having twin-stud insulator and
PTFE bushes provided on each insulator pin.

20. A D.C. traction motor as claimed in claim 1, wherein tapered roller suspension
bearing used for mounting of the motor on bogie axle, which is bolted to the
traction motor magnet frame. (01).

A 167 kW, 675 V, 275 A, 1035 rpm DC traction motor for high power Metro/EMU
application. The frame size of the motor has been made compact and compatible to
broad gauge application. The motor has been designed with class-200 insulation system
resulting higher power to weight ratio and high temperature limits. The new motor has
been designed with taper roller suspension bearing arrangement.