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Blog Entry# 1403331
Posted: Mar 21 2015 (17:51)

5 Responses
Last Response: Mar 27 2015 (21:49)
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Mar 21 2015 (17:51)   TKD/WAP-7/30347
 
guest   6387 blog posts
Entry# 1403331            Tags   Past Edits
--------------------------- REGENERATIVE BRAKING SYSTEM OF ALL 3 PHASE AC ELECTRIC LOCOMOTIVES WHICH SAVE POWER AND ENERGY OF IR ------------------
This blog is dedicated for the "Detailed Discussion" of the Term "REGENERATIVE BRAKING" which is a "Main Feature" of all 3 Phase AC Electric Locomotives(i.e WAP-5,WAP-7 and WAG-9) and which helps railways to save both energy and money. This blog will help this Forum immensely I think.
What is Regenerative Braking?
When
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the driver of a train hauled by 3 phase Locomotive wants to stop or slow down a train, he applies regenerative braking. The motors of the locomotives which are normally pulling the train, change their mode of operation from motor to a generator. The mechanical energy of the train is converted to electrical energy by the generator, which then goes to the power supply grid.(Power Supply grid here means the Overhead Wire). This feature is called regenerative braking. Thus, even braking losses are gainfully utilised in three phase locomotives.
In other words, This is an electrical braking system in which brakes are applied on loco without physical application or brake block failure.
Advantages of Regenerative Braking:
1. Brake block does not apply on wheel so wheel and brake block wear is
eliminated.
2. Reliable braking.
3. Smooth controlling.
4. Energy generated during braking is fed back to OHE i.e. it works just
like a small power station and helps in energy conservation.
5. Braking is available up to 0 KMPH.
Effort of NCR to save energy through Regenerative Braking:
Application of brakes in trains invariably results in loss of energy. However, conservation of energy by utilising the technology of regenerative braking in electric locomotives has helped the North Central Railway to save about 15 million units of electricity costing about Rs six crore in the current financial year.When trains are required to be stopped or slowed down near railway stations or signals, the driver applies brakes. For this purpose, there are mechanical brakes, which work on compressed air, by converting the energy of the motion of a running train to frictional losses.
Pointedly, over the years, the technology upgradation has taken place in electric locomotives, which has contributed in overall objective of Railways to conserve precious electric energy. With this objective in mind, 3 phase locomotives(WAP 5,WAP 7 & WAG 9) were inducted into Railways almost 15 years ago. Initially, these locomotives were imported from Switzerland on ToT basis (Transfer of Technology). As per this agreement, when complete equipment is imported, the foreign company also undertakes to transfer the entire knowhow to the indigenous company for enabling the latter to manufacture the imported equipment in the country. After 5 years, CLW (Chitranjan Locomotives Works) started the production of three phase locomotive indigenously gradually reducing the import content to 5% only.
North Central Railway runs around 250 passenger trains and 150 trains every day by electric locomotives. Out of these, about 25% of trains are run by about three phase locomotives. Since drivers running such locomotives were required to be given special training to utilise this feature, NCR has trained all its drivers to utilise regenerative braking. Due to intelligent application of this feature, NCR has saved about 15 million units of electricity costing Rs 6 crores.
Source of this info: click here
Courtesy: Ashraf Jamal
Source of the "Advantages of Regenerative Braking: Point 6.9.8 in page 36 of the 103 page PDF Document which is already attached with Re# 1400167-40 in /blog/post/1400167 by me.
Inference drawn from above discussion:
3 Phase Locomotive does not need any power from Overhead wire at the time of applying brake to stop or slow down the Locomotive.
So from the above discussion it is also found that "3 Phase Locomotives" also saves Energy and Money of Indian Railways to a great extent through this technology of "Regenerative Braking" which is not present neither in any other Locomotive nor in any EMU DEMU or MEMU trains of Indian Railways.
So, in future in the World of Electric Locomotive Railway should rely on 3 names WAP-5 WAP-7 and WAG -9 for this very important advantage of these 3 Locomotive classes.
Attached Image:
Goods train being helped by a WAP7 from the rear
Pic Courtesy: prdp
Image Link: click here
This Pic is taken from a Video of by prdp the link of which is:
click here
Video Courtesy: prdp
TKD WAP-7 30347
Image Link:click here
All are requested to share views.

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Mar 27 2015 (21:12)
TheMadrasMail~
TheMadrasMail~   6349 blog posts
Re# 1403331-22              
I have seen the document Sir, and I have to say that it was the most detailed document I have seen regarding any Locomotive and it's internal workings. Please don't consider this as an argument, as I believe both 3 phasers and AC-DC locos have their advantages, but I would like to add some more information to clear some misconceptions people seem to be having about AC-DC locos (like the WAP4/WAM4).
To start off, WAP5, WAG9 and WAP7 came with several new features like HOG, regenerative braking, simpler control systems ( Like you mentioned, the loco pilot can change speed by just moving a lever) and also with the newer 3-phase traction motors. The most important thing to
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note is that all these features are present NOT BECAUSE it's a 3 phase loco. These are features that can be implemented in AC-DC locomotives as well and with no need for additional research. The true advantage of 3 phasers is in the acceleration at lower speeds and lower maintenance for the motors ( AC-DC's also have a few advantages). The reason for the more features is a bit interesting.
In locos with DC motors, the speed can be controlled by simply varying the voltage. Of course, there are complications in that as described in your document, but in the end, its just a voltage change. The technology required for this has been available for than a century as it only needs a transformer and a rectifier and it is as simple as a small experiment shown to school students. Induction motors on the other hand, need a change in the input frequency to change speed, they are independent of voltage. Now this is a very complicated system and for a long time, induction motors were useless for locos as they can be run at only one speed since the OHE frequency is fixed.
Only in the recent years, Power electronics have been developed that made it possible to do change frequency and thus make Induction motors actually useful (in fact much more than DC motors in many cases). This is the main reason for the difference in features. The WAP 4 uses a s system that has been in place for several decades now whereas the WAP7's internal systems haven been developed much later. While many advances have been made for AC-DC locos, adding several new features, they haven't been added to IR's fleet of AC-Dc locos.
The WAP7 is definitely a better a locomotive than the WAP4 is almost all aspects, but the reason is not because it is a 3 phaser, the reason is because it was designed much later and it's design required newer technology. Going ahead even the WAP4 (which is more rugged than the current 3 phasers) can be upgraded with the like HOG, regenerative braking, automated control system etc.
Sorry for the long posts, but I have been a long time admirer of the WAM4 and I feel compelled to clear any misconceptions about it. Hope you don't mind:)

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Mar 27 2015 (21:17)
Rishi Trivedi   1570 blog posts
Re# 1403331-23              
After all energy saved is very precious. Thank You Sir for this information! (y) :)
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Mar 27 2015 (21:49)
guest   6387 blog posts
Re# 1403331-24              
There is nothing to mind. It's true. Actually CLW also has a planning to develop HOG systems in WAP-4 Locos but as per the Last Annual Report of RDSO(Year 2011-2012) RDSO gave much preference in 3 Phasers than the Conventional Ones as because if cost constraint is taken into factor to install HOG, and other 3 Phase Features in existing WAP-4 fleet is much more complicated and costly too than retain this WAP-4 class with it's originality. You also well aware of the fact that maintenance cost of WAP-4 is much more than the 3 Phase Locomotives also the present fleet of WAP-4 of IR are not all originally WAP-4 many locos of the WAP-4 fleet was WAP-1 initially then converted to WAP-4. So now these locos are getting old so applying 3 Phase Features on these Locos won't be prudent either technically or physically.
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the material used for WAP-4 Shell and WAG-7 Shell is becoming Limited. So this year may be the last year of production of both of these Locos(WAP-4 and WAG-7) on the part of CLW subject to the availability of Tender for these two Locos. If tender is available then production of these two Locos may continue but in less number than it's 3 Phase Competitors.
The demand for 3 Phasers is now gaining as a result of Which Royapuram gets maximum number of WAP-7 in last Couple of months and many important trains of SR now hauled by RPM WAP-7 in place of WAP-4. In the Coming days WAP-7 will take the place of WAP-4 may be it will take some time but it will definitely happen in future as the present trend is Showing.

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