FIELD OF INVENTION:
The invention relates to traction motors in general, and DC traction motors with improved insulation system (class 200) for board gauge Diesel Electric Locomotive application in particular.
BACKGROUND AND PRIOR ART OF THE INVENTION:-
Many of the Diesel Electric Locomotives which are used for passenger and freight
applications are run by DC traction motors.
Generally, one traction motor is fitted on one axle of the locomotive. The
locomotive has either four or six axles. The Diesel engine of the locomotive
rotates traction alternator which produces the power to feed the DC traction
motors of the locomotive.
Presently, most of the traction motors used in the Diesel Electric Locomotives are
provided with class 'H' insulation. However, 200 class insulation is superior to
class H insulation, as it does not deteriorate at higher working temperatures than

in class H insulation. It also means that 200 class insulation has considerably longer working lite, when exposed to temperatures allowed in class H insulation. In other words it will increase the service life of the motors and reduce their failure.
Therefore, it is preferable to have 200 class insulation in place of class H insulation in the DC traction motor for Diesel Electric Locomotives. The present invention seeks to overcome these drawbacks of the prior art. Due to space limitations, the traction motor should be compact with high power-to-weight ratio. With this view a modified version of traction motor has been designed with class 200 insulation system instead of class 'H' insulation system. This motor shall be able to produce more power with the same frame size. The insulation of the DC traction motor in accordance with the invention is upgraded from class 'H' to 200 class with same motor rating to increase the average life of the machine. During design of the insulation system for a traction machine several factors like mechanical stresses, magnetic forces, temperature rise and cooling medium adopted for the machine need to be considered. The best design would be one which attains the maximum advantage of better performance and high efficiency with longer life in the least possible cost.

OBJECTS OF INVENTION:
The main object of the invention is to provide better insulation to the existing
machine so that the life of the machine can be enhanced for same temperature
rise.
A further object of the invention is to provide a higher rating machine with same
frame size by utilizing the extended temperature rise limit of 200 class insulation.
Yet another object of the invention is to achieve longer service life of the DC
traction motors.
A still further object of the invention is to reduce failure of DC traction motors
due to insulation failure, thereby reducing cost of maintenance.
SUMMARY OF INVENTION:
The new improved traction motor is designed based on new insulation scheme of class 200. The class 200 insulation scheme is designed for this machine with polyimide tape, PTEE tape, silicone bonded mica paper tape with polyimide backing, silicone treated woven glass tape and polyamide washer. The external dimensions of the motor is same as in its previous version with class H insulation and some design modifications have been done depending on the new class 200 insulation scheme.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:-
Fig. 1: shows the sectional diagram of the traction motor according to the
invention. Fig. 2: shows the modified class 200 insulation scheme for traction motor
armature according to the invention. Fig. 3: shows the modified class 200 insulation scheme for traction motor series
field according to the invention. Fig.3: shows the modified class 200 insulation scheme for traction motor
compote coil according to the invention. The invention will now be described in an exemplary embodiment as depicted in the accompanying drawings. There may however be other embodiments of the invention, all of which are deemed covered by these specification.
CONSTRUCTIONAL FEATURE OF A TRACTION MOTOR:-
1. MAGNET FRAME:-
The high permeability steel magnet frame is machined to ensure alignment of the end shields, pole bores and axle ways. The nose of the motor is resiliently supported in the bogie of the locomotive.

The end shields (02, 03) are spigoted into frame with slight interference fit and held in position by means of bolts which are suitably locked. This method of mounting ensures that the fit between the end shield and the frame remains tight in service. Roller bearings (04, 05) are provided and labyrinths are formed to prevent the escape of lubricating grease or the entry of dirt or moisture. Greasing vents are provided on topside of both housings with grease nipples (06).
2. Armature:-
The armature core (07) is built from electrical quality low loss sheet steel laminations insulated from each other and assembled on the shaft (08) with interference fit and consolidated under pressure. The laminations are held together between endplates (09, 10) fitted on the shaft machined from nickel-chronium-molybdenum steel bar, hardened & tempered. The armature is lap wound. The armature conductors are insulated with mica based Class 200 insulation. The coils (11) are held down in the core slots with polyimide slot wedges (12) and Res-I-glass bands (13) retain the end portions of the coils. The wound armature is finally vacuum pressure impregnated in solvent-less polyesterimide varnish.

The armature bearing (04, 05) assemblies are of sealed type provided with adequate labyrinths to avoid the contamination of the lubricating grease with dirt, moisture cardium compound.
3. COMMUTATOR;-
The commutator (14) is of arch bound construction. The copper segments (15) are made from hard drawn silver bearing copper and risers integral with segments are slotted to receive the armature coil leads. The armature coil leads are finally TIG welded to commutator risers (16).
The copper segments which are insulated from each other with the micanite segments, are held together with the Steel 'V' (17) rings insulated with the molded V-rings. The exposed surface of the commutator front micanite V-ring is covered with PTFE bush (18) to obtain high creepage. Replaceable arcing ring is provided to minimize the damage to the commutator and brush gear in the event of any flashover.
4. POLES AND FIELD COILS:
The main poles (19) are built up from steel laminations riveted together. The main field coils (20) are made of copper strap wound on flat, whereas the

compole (21) coils (22) 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.
5. BRUSH GEAR:-
There are four brush arms, each carrying a brush holder (23) with three carbon brushes (24). 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.
6. GEARS AND GEARCASE:-
Gear case (25) has top mounted bolting arrangement to reduce vibration.
7. AXLE SUSPENSION BEARINGS:-
Locomotive 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.

TECHNICAL SPECIFICATION OF THE TRACTION MOTOR IN ACCORDANCE WITH THE INVENTION:
The traction motor of the invention is an especially designed motor for high speed broad gauge diesel electric locomotives. It is a DC series wound, four pole, and forced ventilated traction motor suitable for axle mounting on taper roller suspension bearing. It is supported on the nose by a resilient suspension unit. It complies to IEC-60349:2001/IEEE-11:1982.
RATING;
Maximum voltage : 1100 Volt DC
Maximum current : 1400 AMPS DC
Class of Insulation : Class 200
Gear ratio : 18.65/18.74
Weight of traction motor : 3925 ±50Kg.
(With pinion gear wheel, gear case
and taper roller bearing arrangement)
Ventilation : 2300 CFM
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 depends upon the life of the insulation. The

excessive temperature rise may cause insulation failure. If the machine is continuously operated above the specified temperature limit, the life of the insulation and hence the life of the machine will be reduced. By providing proper ventilation and cooling, the temperature rise can be kept within the safe limit. With this view a modified version of traction motor has been designed with class 200 insulation system.
In armature coil insulation as seen in Fig. 2, polyimide tape is used as a base insulation and after that PTFE tape, silicone bonded mica paper tape with polyimide backing, silicone treated woven glass tape and polyamide tape is lapped around the conductor. In prior art, epoxy bonded glass mica tape and woven glass tape were used to wind the coil.
As illustrated in Fig. 3, main field coil conductors are separated by polyamide tape and each section is lapped with silicone treated woven glass tape individually on three sides (other than lead end). Then complete coil is wound with polyamide tape, silicone bonded glass baked mica paper tape and silicone treated woven glass tape. First and second turns of each section is reinforced with silicone bonded glass baked micanite. At corners of conductor glass mica glass is used to increase the strength of the insulation. In between upper and lower part of coil silicone asbestos putty is used. In prior art, woven glass tape and epoxy bonded glass mica tape were used to wind the coil.

In compole coil (Fig.4), polyamide washer is used as interturn insulation. End turns of coil are insulated with polyimide tape and glass mica washer 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. In prior art woven glass tape and epoxy bonded glass mica tape were used to wind the coil.
Vacuum pressure impregnation (VPI) of armature, main field and compole coil is made by FT2005/RE009 polyesterimide varnish. In prior art FT1052 was used for VPI.

We Claim:
1. 280KW DC traction motor with 200 class insulation for broad gange Diesel Electric Locomotives comprising of high permeability steel magnet frame (01), end shields (02,03), armature having armature core (07) built from electrical quality low loss sheet steel laminations insulated from each other and assembled on shaft (08) a plurality of armature coils, commutator (14) of arch bound construction, a plurality of main poles(19), compoles (21) and field coils (20), a plurality of brush arms having brush holder (23) and carbon brushes (24), a plurality of gears and gear cases (25), armature bearings (04, 05) and axle suspension bearings, characterized in that the traction motor is provided with 200 class insulation to enhance the life of the motor for same temperature rise.
2. A 200KW DC traction motor as claimed in claim 1, wherein the nose of the motor is resiliently supported in the bogie of the locomotive.
3. A 200KW DC traction motor as claimed in claim 1, wherein end shields (02, 03) are spigoted into frame (01) and are held in position by means of bolts which are locked.
4. A 200KW DC traction motor as claimed in claim 1, wherein the said armature coils are insulated with silicone bonded mica paper tape with polyimide backing

to make the insulation class 200 and polyamide tape is lapped around conductors after treated woven glass tape to provide extra mechanical strength.
5. A 200KW DC traction motor as claimed in claim 1, wherein conductors of the
main field coils (20) are wound with polyamide tape, silicone bonded glass baked
mica paper tape and silicone treated woven glass tape to make the insulation
class 200, the corners of the coils (20) being provided with glass mica glass to
increase mechanical strength.
6. A 200KW DC traction motor as claimed in claim 1, wherein the compole (21)
coils have polyamide washers as interturn insulation, the end turns of the coils
being insulated with polyimide tape and glass mica washers on the outside and
the coils are lapped with silicone bonded glass baked mica paper tape and
silicone treated woven glass tape to provide class 200 insulation.
7. A 200KW DC traction motor as claimed in claim 1, wherein the wound
armature, poles and coils are vacuum pressure impregnated after being insulated
with class 200 insulation and then encapsulated in solventless polyesterimide
varnish.

280KW DC traction motor with 200 class insulation for broad gange Diesel Electric Locomotives has a high permeability steel magnet frame (01). The armature has armature core (07) built from electrical quality low loss sheet steel laminations insulated from each other and assembled on shaft (08). A plurality of armature coils, commutator (14) of arch bound construction, a plurality of main poles(19), compoles (21) and field coils (20), a plurality of brush arms having brush holder (23) and carbon brushes (24) are provided. It has a gears and gear cases (25), armature bearings (04, 05) and axle suspension bearings. The traction motor is provided with 200 class insulation which enhances the life of the motor for same temperature rise.