Field of the invention:
The invention relates to the field of electric locomotives in general and to a 282 KW light weight DC series traction motor for diesel electric locomotives in particular.
Background and prior art:
Indian Railways is running a large number of passenger & goods trains for passengers & goods. Diesel electric and AC locomotives are used to run many of the trains. The Diesel electric locomotives are manufactured at Diesel Locomotive Works (DLW), Varanasi. All rotating electrical equipment viz. traction alternators, traction motors & other auxiliary machines are manufactured and supplied by the applicant to DLW, Varanasi. These equipment are installed in the locomotives as prime movers and auxiliaries.
Generally, traction motors are mounted on the 6 axles of a locomotive. These motors get power from a traction alternator mounted on the locomotive floor which is driven from a diesel engine mechanically coupled to the alternator.
It is imperative that any reduction in the total weight of the locomotive leads to reduction of its fuel consumption and higher speed . Hence a need for reduction in weight and size of the traction motors has always been felt.
On demand from M/S Indian Railways for a lighter weight traction motor suitable for high speed broad gauge diesel electric locomotive application, the applicants

undertook this challenging job to develop a traction motor which can meet the light weight and high stability requirement of the application to run the loco at a very high speed of 160 kmph. Accordingly, the applicants developed a new DC series traction motor with a reduction of weight by about 550-600 kgs when compared to the existing traction motors for similar application, which meets all the electrical & mechanical design parameters of the customer.
Weight reduction (Light weight) is one of the major goals in this development. Lighter vehicles perform better and cost less to operate because they are more energy efficient and can also attain very high speeds. On the other hand they can accelerate at a much higher rate. This opens the possibility for Diesel Engine Drives to compete with Electric engine drives for suburban commuter traffic routes.
The light weight DC series traction motor in accordance with the present invention overcomes the above drawbacks of the prior art.
Objects of the invention:-
An object of the invention is to provide a light weight 282 kW DC series traction motor for diesel electric locomotives for Indian Railways. Another object of the invention is to provide an improved DC traction motor having comparatively higher power to weight ratio, thus enabling lighter axle load on locomotives for better service performances.
Yet another object of the invention is to provide a 282 KW DC traction motor that is more compact and therefore reduces overall size of a diesel-electric locomotive.

A further objective of the invention is to provide a DC traction motor which leads to saving of fuel.
Description of the invention:
The applicants took the initiative for indigenous design and development of the lightweight 282 kW DC traction motor for use in diesel electric locomotive. This traction motor is of very compact and lightweight construction having high power to weight ratio. The improved traction motor is designed based on innovative modifications carried upon the existing proven traction motors. Important consideration in this development was to ensure the fitment of motor in the bogie of a new locomotive along with reduced tare weight of the locomotive axle. The external dimensions of the motor were finalized to suit the boundary limits of broad gauge applications. Initial designs were worked out and material specification of critical components, insulation scheme and bearing arrangement etc were finalized to achieve desired motor performance.
Brief description of the accompanying drawings:
Fig. 1 shows the magnet frame of the traction motor according to the invention.
Fig. 2 shows the magnet frame of the traction motor of prior art.
Fig. 3 shows cross-sectional view of the traction motor according to the
invention.
Fig. 4 shows the plan of brush holder body. Fig. 5 shows the elevation of brush holder spring details. A preferred embodiment of the invention will now be described with the help of above drawings. There may however be other embodiments, all of which are deemed covered by this description.

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-l 1:1982.
Rating
Maximum voltage : 1120 Volt DC
Maximum current : 1400 AMPS DC
Class of Insulation : Class 'H'
Gear ratio : 2.773
Weight of traction motor : 3250 ±50 Kg.
With pinion gear wheel, gear case
and taper roller bearing arrangement.
Ventilation : 2300 CFM
CONSTRUCTIONAL FEATURES OF THE TRACTION MOTOR:
1. Magnet Frame (Refer Fio.l)
The high permeability steel frame (1) 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.
The end shields (item 001 & 002 of fig. 3) 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 (item 003 & 004 of fig. 3) are provided and labyrinths (item 005 & 006 of fig. 3) are formed to prevent the

escape of lubricating grease or the entry of dirt or moisture. Greasing vents are provided on topside of both bearing housings with grease nipples. Armature (item 007 of fig. 3)
The armature core is built from electrical quality low loss sheet steel laminations insulated from each other and assembled on the shaft (item 008 of fig. 3) with interference fit and consolidated under pressure. The laminations (item 009 of fig. 3) are held together between endplates (item 010 & 011 of fig. 3), fitted on the shaft machined from nickel-chromium-molybdenum steel bar hardened & tempered.
The armature is lap wound. The armature conductors are insulated with mica based Class "H" Insulation system. The coils (item 012 of fig. 3) are held down in the core slots with polyimide slot wedges, and Res-l-glass bands retain in the end portions of the coils. The wound armature is finally vacuum pressure impregnated in solvent-less polyesterimide varnish. Armature end plate is redesigned with straight ribs instead of Y shaped ribs for better strength. Special commuter hub designed for increased ventilation.
II. Commutator(Item 013 of fig.3)
The commutator is of arch bound construction. The copper segments 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.
The copper segments which are insulated from each other with the micanite
segments, are held together with the Steel V rings, insulated with the molded
micanite V-rings. The exposed surface of the commutator front micanite V-ring is
covered with PTFE bush 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. Epoxy molded ring used at the coils overhang portion to reduce the commutator hub weight and reduction in insulating materials.
III. Poles and Field Coils (item 014 of fig. 3)
The poles are built up from steel lamination riveted together. The main field coils are made of copper strap wound on flat, whereas the compole coils are edge wound. The coils are insulated with Class lH' insulating materials. Pole & Coils assembly together is vacuum pressure impregnated & encapsulated in solventless polyesterimide varnish.
IV. Brush Gear
There are four brush arms, each carrying a brush holder (4) with three carbon brushes. 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.
V. Gears and Gearcase (item 015 of fig. 3)
Gear case has top mounted bolting arrangement to reduce vibration .
VI. 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.
VII. Armature Bearings:
The bearing assemblies are of sealed type provided with adequate labyrinths to avoid the contamination of the lubricating grease with dirt, moisture cardium compound.

As stated earlier, the main object of the invention is to achieve both weight and size reduction of the traction motor, while retaining its performance. This object is realized primarily by the undermentioned innovations.
1. Reduction of magnet frame (item 1.5 of Fig. 1) thickness to 53.5 mm from 55
mm in prior art.
2. Reduction of total length of magnet frame (item 1.1) from 1008 mm to 926
mm.
3. Reduction of commutator daimer (item 013 of Fig. 3) from 424 mm to 380
mm.
4. Reduction of core length (item 009 of Fig. 3) from 394 mm to 360 mm.
The traction motor of the invention is lighter by about 550-600 Kgs in comparison with a traction motor of prior art, for similar application.
Outstanding features of the traction motor according to the invention are:
A. It is a 282 Kw DC Traction motor weighting 3250+50Kg approx.
B. This motor is designed to fit in board gauge diesel electric locomotives
suitable for 160 kmph.
C. This traction motor can be used in goods, mixed and passenger traffic
applications.
D. This motor has been designed to suit the ventilation provided by the existing
blower motor used by M/s DLW Varanasi.
E. Higher power to weight ratio with respect to the existing machines for the
similar application.

F. Center distance between axle centerline & armature centerline has been retained
same so that the existing locomotive bogie of IR can be used for this motor also.
G. Weight reduction (Light weight)is one of the major goals in this developments.
Lighter vehicles perform better and cost less to operate because they are more energy
efficient and can also attain very high speeds. On the other hand they can accelerate at
a much higher rate. This opens the
opportunity for diesel engine drives to compete with electric engine drives for suburban commuter traffic routes. DIFFERENTIATING FEATURES

We Claim:
1. A light weight DC series traction motor (3) comprising of high permeability
steel magnet frame (1), armature (007) built from electrical quality low loss
sheet steel laminations (009) insulated from each other and assembled on the
shaft (008), commutator (013), poles and field coils (014), a plurality of brush
gears having brush holders (4), gears and gear cases (015), axle suspension
bearing and armature bearings,
characterized in that said traction motor has a power to weight ratio pf 0.97 and a core to commutator ratio of 1.315.
2. A DC traction motor as claimed in claim 1, wherein the armature (007) has lap
wound coils (012) which are held down on the core slots with polyimide slot
wedges to reduce armature weight.
3. A DC traction motor as claimed in claim 1, wherein the commutator (013) has
epoxy molded ring at the coil overhang portion to reduce weight.
4. A DC traction motor as claimed in claim 1, wherein the commutator (013) is of
arch bound construction and is provided with replaceable arcing horns.
5. A DC traction motor as claimed in claim 1, which has external dimensions to
suit the boundary limits of brood gauge applications.
6. A DC traction motor as claimed in claim 1, wherein the armature bearing
assemblies are of sealed type with adequate labyrinths to avoid contamination of
the lubricating grease.

A light weight DC series traction motor (3) comprising of high permeability steel magnet frame (1), armature (007) built from electrical quality low loss sheet steel laminations (009) insulated from each other and assembled on the shaft (008), commutator (013), poles and field coils (014), a plurality of brush gears having brush holders (4), gears and gear case (015), axle suspension bearing and armature bearings,
characterized in that said traction motor has a power to weight ratio pf 0.97 and a core to commutator ratio of 1.315.