3. Prior Art
3.1 Background
Rail coaches are generally provided with electrical power for lighting and cooling fans. With the developments in technology and to improve passengers' comforts and conveniences, provisions are being made to operate air-conditioners, and pantry equipment like refrigerators and ovens, as well. Such electrical power requirement are termed as 'utility or hotel load' and is sourced either from a Captive or Self Generation (SG) system of the coach or from a Head-on-Generator or an End-on-Generator (EOG), with such system connected to a group of coaches of the train. These systems are briefly described as follows:-
3.1.1 Self generation System: Self Generation (SG) System is a conventional electrical power generation system and is a captive source of electrical power for the respective passenger coach. The system has an electrical generator coupled to the Axle/s of the passenger coach, along with complimenting batteries, inverters, pulley, belts, regulator and battery box etc. Capacity of such system is selected as per the electrical power requirement (1 x 4.5 kW per standard coach and 2 x 25 kW per AC coach, etc). This system is used on all the conventional mail, express & passenger trains except the fully AC trains.
3.1.2 End-on-Generation System: End on Generation (EOG) is a system used on air conditioned(AC) trains of Indian Railways and dates back to 1960's or even earlier. This
system comprised a Diesel Generator (DG) set mounted inside a dedicated coach termed
as Power Car. Such DG set provides electrical power to Air-conditioned Coaches and
Dinning & Pantry cars etc. of such trains. In technical term, the power generated by DG
sets is utilized for hotel load of the train.
Depending upon the requirement of Hotel Load, the number of EOG/s provided to such
trains can be one or two. However, with the increasing popularity of AC trains,
provisioning of two EOGs for each train has become a common practice.
3.1.3 Head-on-Generation System: Head-on-Generation system is a very much prevalent
system of meeting the utility load requirement of passenger trains in many railways the
world over and has been recently introduced in India too.
In this system, utility power is generated on conversion of traction power. This conversion
takes place in a dedicated winding provided in the transformer of the electric locomotive
attached to the rake(group of passenger coaches). In other words, the transformer of the
electric locomotive an additional winding provided for the purpose.
3.2 In context of Indian railways, SG and EOG systems are very much prevalent. The
third system, viz. HOG has been recently introduced for meeting the utility load
requirement of fully air-conditioned trains like Rajdhani Express. In an ingenious effort,
surplus capacity of the auxiliary winding of the locomotive has been tapped for the utility
load. These two types of HOGs, are referred to as 'Rajdhani' and 'Saptagiri' systems
respectively in the subsequent write-up.
As on date, utilization of electrical energy from the two HOG systems needs either an
individual or bulk converter to convert the single phase power to three phase.
3.3 SG System has the following basic components:-
3.3.1 Alternator - to generate electrical energy from the mechanical energy of moving axles
3.3.2 Rectifiers - to covert AC power from Alternator to DC power
3.3.3 Battery - for storage of electrical energy
3.3.4 Inverter - to covert DC power from Battery to AC power, single phase

3.3.5 Step-up Transformer or Pre-cooling Transformer - for stepping the voltage of electrical power obtained from the inverter
3.3.6 Converter - for converting the single phase stepped up AC power to three phase AC power for utilities.
In addition, there are components for safety and controls like switches and fuses etc.
While the components from 3.3.1 to 3.3.3/3.3.4 are common to all passenger coaches,
though their specifications are different, 3.3.1 to 3.3.6 form the part of utility power
supply in AC Coaches with SG System.
Diagrams 1.1 and 1.2 depict such systems for AC & non-AC coaches.
Note :- Sequencing of the components may not be exactly3.3.1 to 3.3.6.
4. Drawbacks of Prior Art
4.1 SG system is although the most prevalent utility power sources with the Indian
Railways but this system is highly techno-economically in-efficient in terms of cost of
operation and efficiency as also it blocks locomotives' power which is otherwise meant
for haulage and hence there would have been a quest for an efficient alternative.
But none the less, being a captive system, it imparts the advantages of flexibility and versatility.
4.2 The EOG System is the widely used alternative and off late Indian Railways have are conducting trials with HOG system.
4.3 Sourcing of utility power from HOG System is though the most efficient alternative but its adoption/utilization needs extensive and/or expensive re-engineering of existing coaches by way of individual or bulk converter to convert the single phase power to three phase before feeding the intended utilities .
5. The Invention
5.1 Patent application submitted here-in is for modification/retrofitting of electrical circuits of the existing SG Coaches of Indian Railways and is titled as :-' Retrofitting of Self Generating (SG) System of Passenger Coaches for Compatibility with Traction Power'.
The modification/retrofitting suggested will enable the electrical equipments of the passenger coach otherwise operating on SG System, to operate on the single phase AC power supplied by the HOG or TPC without any additional phase converter/s (bulk or individual).
Note :- The Traction Power Converter or TPC consists of electrical equipment assembled to draw electrical power from the traction line and render it suitable for operation of utilities of the passenger train to which it is attached with/or without any further electrical activity e.g. step-up/step-down, rectification/inversion etc.
5.2 In this invention, characteristics of electrical power's input and output at various
components of the SG System are put to use, so as to yield an optimum system to meet
the Hotel/Load of the passenger coach.
5.3 The Invention can be applied in several ways to provide a traction power based
electrical power supply system for the utilities. For example.-
5.3.1 Substitute the electrical power from alternator by that of HOG/TPC and this arrangement will yield a Universal Power System which will work both on electrified and non-electrified tracks. This switch-over from Alternator to HOG/TPC s electrical power system could be automatic or manual.
The single phase AC power needs to be stepped down to match the specifications of power output from the alternator and for this purpose a suitable transformer is provided. Such addition along with the cost of and electrical power cable will need investment but this will be just a fraction of the entire SG System.
This arrangement is depicted in Diagram 2.1 and 2.2 for AC & non-AC coaches respectively.
It imparts the utmost flexibility in operation with the retrofitted system being capable of meeting the utility power requirement of the respective coach on the electrified as well as non electrified (mixed) tracks.
5.3.2 Connect the electrical power from TPC to the input of either the pre-cooling transformer or of static converter. While the former arrangement will need a suitable step-down transformer, the later may not need any step-down or step-up component/s. These arrangements are depicted in Diagram 3.1 and 3.2.
Components like alternators, battery, rectifier and inverter would no longer be needed. The only additional components required in retrofitting would be a step down transformer and electrical power coupling cables. Their cost would be less than the salvage value of the redundant components. Coaches with such retrofitting can be used only on electrified tracks.
6. Benefits of the Invention
The invention will find application in the SG System based coaches of passenger trains being operated on electrified as well as electrified-cum-non-electrified tracks; in meeting the utility/hotel power requirements. It is expected to provide cleaner and cheaper alternative source of utility/hotel power to operate the utilities of passenger coaches and will provide the following advantages:-
6.1 On electrified tracks with HOG/TPC power system in operation:-
6.1.1 Higher conversion efficiency vis-a-vis the original SG System; almost double. Thus the cost of energy and pollution will be halved.
6.1.2 No drag on locomotive; thus releasing much needed power, otherwise locked up for electrical power generation by the SG System.
6.1.3 Negligible or little cost of retrofitting.
6.1.4 Lower operating and maintenance cost of the retrofitted system.
6.1.5 In case of retrofitting for exclusive use on electrified tracks, the cost of retrofitting would be more than offset by the realization from disposal of redundant components.
6.2 On electrified as well non-electrified (mixed) tracks:-
While on electrified part/section of tracks, the Universal Power System, which is
essentially a retrofitted SG System suitable for operation on mixed tracks; will yield the
benefits stated in para 6.1.1 and 6.1.2.
There will little or negligible additional cost while operating on non-electrified tracks.
This will be more than offset by the gains realized from operation the coach on electrified
tracks.
7. Applicability. -
7.1 The invention will find application on the coaches of passenger trains being operated
on electrified as well as electrified-cum-non-electrified (mixed) tracks; in meeting the
utility/hotel power requirements of passenger coaches.
7.2 The envisaged retrofitting is simple, quick and inexpensive and thus can be
implemented quickly without straining the resources.

8. Claim/s
8.1 Patent application submitted here-in is for modification/retrofitting of electrical
circuits of the existing SG Coaches of Indian Railways and is titled as :-
'Retrofitting of Self Generating (SG) System of Passenger Coaches for Compatibility with Traction Power'.
The modification/retrofitting suggested will enable the electrical equipments of the passenger coach otherwise operating on SG System, to operate on the single phase AC power supplied by the HOG or TPC without any additional equipment like phase converter/s (bulk or individual).
8.2 In this invention, characteristics of electrical power's input and output at various components of the SG System are put to use, so as to yield an optimum system to meet the Hotel/Load of the respective passenger coach.
8.3 The Invention can be applied in several ways to provide a traction power based electrical power supply system for the utilities. For example:-
8.3.1 Substitute the electrical power from alternator by that of HOG/TPC and this arrangement will yield a Universal Power System which will work both on electrified and non-electrified tracks. The switch-over from Alternator to TPC could be automatic or manual. The single phase AC power needs to be stepped down to match the specifications of power output from the alternator and for this purpose; a suitable transformer is provided. Such addition along with the cost of and electrical power cable will need investment but this will be much less compared to that of the SG System.
This arrangement is depicted in Diagram 2.1 and 2.2 for AC & non-AC coaches respectively. It has the utmost flexibility in operation with the retrofitted system being capable of meeting the utility power requirement of the respective coach on the electrified as well as non electrified tracks.
8.3.2 Connect the electrical power from TPC to the input of either the pre-cooling transformer or of static converter. While the former arrangement will need a suitable step-down transformer, the later may not need any step-down or step-up component/s. These arrangements are depicted in Diagram 3.1 and 3.2.
Components of the SG system like Alternator, Rectifier/s, Battery, and Invertor will be redundant. The only additional components required in retrofitting would be a step down transformer and electrical power coupling cables. Cost of additions would be less than the salvage value of the redundant components. Coaches with such retrofitting could be used only on electrified tracks. 8.4 Retrofitting, envisaged in the Invention, provides Techno-economically viable alternatives with little or no investment. 8.5 The invention will yield following advantages:-8.5.1 On electrified tracks with HOG/TPC power system in operation:-
8.5.1.1 Higher conversion efficiency vis-a-vis the original SG System; almost double. Thus the cost of energy and pollution will be halved.
8.5.1.2 No drag on locomotive; thus releasing much needed power for haulage which is otherwise locked up for electrical power generation by the SG System.
8.5.1.3 Negligible or little cost of retrofitting.
8.5.1.5 In case of retrofitting for exclusive use on electrified tracks, the cost of
retrofitting would be more than offset by the realization from disposal of redundant
components.
8.5.2 On electrified as well non-electrified (mixed) tracks:-
While on electrified part/section of tracks, the Universal Power System, which is
essentially a retrofitted SG System suitable for operation on mixed tracks; will yield the
benefits stated in para 8.5.1.1 and 8.5.1.2.
There will little or negligible additional cost while operating on non-electrified tracks and
this will be more than offset by the gains realized from operation on electrified tracks.
8.6 Adoption of the envisaged retrofitting will help in extension of HOG/TPC based power supply system to partial AC trains as well as AC and partial AC trains operating on a combination of both electrified and non-electrified (mixed) tracks and their coaches having SG System.
8.7 The envisaged retrofitting is quick and inexpensive and thus can be implemented quickly.
transformer and electrical power coupling cables. Cost of additions would be less than
the salvage value of the redundant components.
Coaches with such retrofitting could be used only on electrified tracks.
9.4 The invention will find application in the SG System based coaches of passenger trains being operated on electrified as well as electrified-cum-non-electrified tracks; in meeting the utility/hotel power requirements.
9.5 It is expected to provide cleaner and cheaper alternative source of utility/hotel power to operate the utilities of passenger coaches.
9.6 It will help eliminating the drag of SG System on locomotive; thus releasing much needed loco power, otherwise locked up for electrical power generation by the SG System; for haulage of the respective train.
9.7 Retrofitting, envisaged in the Invention, provides Techno-economically alternatives with little or no investment and thus can be implemented quickly.