Indian locomotive class WAP-4

{{Short description|Indian Railway passenger class electric locomotive}} {{Use dmy dates|date=May 2019}} {{Use Indian English|date=May 2019}} {{Infobox locomotive | name = WAP-4 | image = AJJ WAP4.jpg | caption = Arakkonam based WAP-4 at Bilaspur Jn. | powertype = Electric | builder = Chittaranjan Locomotive Works | gauge = {{Track gauge|5ft6in|lk=on}} | poweroutput cont = {{convert|5050|hp|kW|0|abbr=on}} | maxspeed = {{convert|140|km/h|mph|0|abbr=on}} | poweroutput = {{convert|5350|hp|kW|0|abbr=on}} | t/e starting = {{convert|30800|kgf|kN lbf|abbr=on}} | serialnumber = | builddate = 1993-2015 | uicclass = Co'-Co' | bogies = Co-Co Flexicoil Mark 90 cast bogies; primary and secondary wheel springs with bolsters | wheeldiameter = New: {{convert|1092|mm|ftin|0|abbr=on}}<br />Half worn: {{convert|1055|mm|ftin|abbr=on|frac=2}}<br />Full worn: {{convert|1016|mm|ftin|0|abbr=on}} | length = {{convert|18.794|m|ftin|abbr=on|frac=32}} | height = {{convert|4.272|m|ftin|abbr=on|frac=32}} | width = {{convert|3.179|m|ftin|abbr=on|frac=32}} | axleload = {{convert|18800|kg|abbr=on}} | locoweight = {{convert|116000|kg|abbr=on}} | tractionmotors = Hitachi HS15250 | locobrakes = Air | trainbrakes = Air | safety = Slip control, Over voltage relay, Main overload relay, Earth Fault Relay, Low Pressure Governor, Brake Cylinder Cutoff Valve, Train parting alarms and No OHE volt relay | operator = Indian Railways | fleetnumbers = '''22061''' and from '''22201'''-'''22399''', '''22500'''-'''22999''' & '''25000-25051''' | totalproduction = 778 | aarwheels = C-C | electricsystem = {{25 kV 50 Hz}} Overhead | collectionmethod = Pantograph | locale = All over India | disposition = Active }}

The Indian locomotive class '''WAP-4''' is a class of 25 kV AC electric locomotives that was developed in 1993 by Chittaranjan Locomotive Works for Indian Railways. The model name stands for broad gauge (W), AC Current (A), Passenger traffic (P) locomotive, 4th generation (4). They entered service in late 1994. A total of 778 WAP-4 were built at CLW between 1993 and 2015, which made them the most numerous class of mainline electric passenger locomotive until the introduction of WAP-7 in 2000<ref name=":0" />.

The WAP-4 is one of the most successful locomotives of Indian Railways{{Peacock inline|date=August 2024}} serving passenger trains for over 29 years. This class provided the basic design for other locomotives like the WAP-6. Despite the introduction of more modern types of locomotives like WAP-7, a significant number are still in use, both in mainline duties. Production of this class was halted in December 2015 with locomotive number 25051 being the last unit to be rolled out.

As of November 2025, all locomotives except those lost in accidents still retain "operational status" on the mainline as WAP-4, with further examples having been converted from WAP-6.<ref name=":0">{{Cite web |title=Listing All Locos - IRFCA Locomotive Database |url=https://www.irfca.org/apps/locos?filter_term%5Bloco_class_id%5D=7 |access-date=2025-03-26 |website=www.irfca.org}}</ref>

== History == === Development === The WAP-4 class was developed after its predecessor, the WAP-1, was found inadequate to haul the longer, heavier express trains (24-26 coaches) that were becoming the mainstay of the Indian Railways network. IR/RDSO had realized that the reason for the WAP-1’s performance problems were the low-powered 770 hp Alstom TAO 659 traction motors. These were previously used with for the WAM-4 and WAG-5 classes but were too underpowered for modern requirements. At that time, new 840 hp Hitachi 15250 traction motors which had been adopted for use on newer WAG-5s was showing promise. So, these traction motors were adopted on to WAP-1s Flex-icoil Mark I fabricated bogies, and with a new indigenously designed 5400 kVA transformer and silicon rectifiers.<ref>{{cite web |url=https://www.rdso.indianrailways.gov.in/works/uploads/File/29_01_10.pdf |title=RDSO document |last= |first= |date=29 January 2010 |website=www.rdso.indianrailways.gov.in |publisher= |access-date=12 September 2024 |quote= |archive-url=https://web.archive.org/web/20220729170706/www.rdso.indianrailways.gov.in/works/uploads/File/29_01_10.pdf |archive-date=29 July 2022}}</ref>

It also was among the first locomotives to get a microprocessor-based control and fault diagnostics system. To accommodate the heavier Hitachi motors without increasing its 112t overall weight, the WAP-4 was made substantially lighter by the widespread use of aluminum materials in construction. The underframe of WAP-4 is narrower and lighter and also completely different from that of the WAP-1 to enable it to handle higher loads.<ref>{{cite web |url=https://rdso.indianrailways.gov.in/works/uploads/File/Maintenance%20handbook%20on%20Flexicoil%20Bogies%20Mark-I(1).pdf|title=FLEXICOIL BOGIES MARK - I |last=Maharajpur |first=Gwalior |date=May 2002 |website=rdso.indianrailways.gov.in |publisher= |access-date= |quote= |page= }}</ref>{{Page needed|date=July 2024}}<ref>{{cite web |url=https://rdso.indianrailways.gov.in/uploads/files/TC%2074.pdf |title=Procedure for Welding of Centre Pivot Pin to The Underframe of WAP-4 & WAG-7 Locomotives. |author= |date=October 2001 |website=rdso.indianrailways.gov.in |publisher= |access-date= |quote= |page= }}</ref>{{Page needed|date=August 2024}}

=== Design === thumb|200px|(''front'') newer loco with (''back'') older series unit The loco has a streamlined twin cab carbody design, with top-mounted headlamps. The first 150 or so units had the headlamp mounted at waist level, with the lights being mounted in a protruding nacelle. Later on the headlamps were placed in a recessed nacelle, and from road # 22573 onward, the headlamps were moved to the top. Newer locos also feature larger windshields, more spacious driver cabin with bucket type seats and ergonomic controls. The control panel also features a mix of digital and analog displays in newer units (all analog display in older versions).<ref>{{cite web |url=https://www.ijmer.com/papers/Vol4_Issue4/Version-1/A044010114.pdf |title=Study on Bogie and Suspension System of an Electric Locomotive |author= |date=April 2014 |website=www.ijmer.com |publisher= |access-date= |quote= |page= |issn=2249-6645}}</ref>{{Page needed|date=August 2024}}

=== Production === The first WAP-4 unit, #22201 rolled out from CLW on April 25, 1994. They looked exactly like the WAP-1, even sporting the same livery. From 2000, newer versions with many WAP-5 design cues like square type windscreens, twin-beam headlights, speed recorders and some changes to the control electronics had been rolled out recently.{{Citation needed|date=August 2024}}

However, in the face of the advent of three-phase AC traction motors, IGBT-controlled AC drives, and full computer controls, the DC traction motors were getting increasingly outdated. As a result, after over 20 years, production of the WAP-4 locomotives ceased on November 1, 2015, with the 776th unit, #25051, being rolled out.<ref>{{cite web |url=https://rdso.indianrailways.gov.in/works/uploads/File/37th%20MSG%20Minutes.pdf |title=MINUTES OF XXXVII MAINTENANCE STUDY GROUP (ELECTRIC LOCO) MEETING |author= |date=24-25 July 2015 |website=rdso.indianrailways.gov.in |publisher= |access-date= |quote= |page= }}</ref>{{Page needed|date=August 2024}}

== Service == The WAP-4s were developed at the same time IR gave procurement orders for WAP-5 locomotives, as they were meant for more general duties of hauling 24-coach expresses while WAP-5 were specially meant for high-speed operations.{{Citation needed|date=August 2024}}

Recently{{When|date=August 2024}} as per directive received from Railway Board,{{Which|date=August 2024}} all the loco sheds holding WAP-4 type locomotives have started multiple unit (MU) operations. This configuration of MU-fitted WAP-4 locos are being used to haul medium tonnage faster freight trains across IR. The different locomotive sheds of WAP-4 are Arakkonam, Santragachi, Erode, Mughalsarai, Howrah and Bhusaval.<ref>{{cite web | url=https://www.thehansindia.com/news/cities/visakhapatnam/waltair-division-to-use-wap-4-model-locos-for-freight-operations-645393 | title=Waltair Division to use WAP-4 model locos for freight operations | date=14 September 2020 }}</ref>

[[File:WAP-4_Rail_Engine_at_Dhubulia_Railway_Station.jpg|thumb|Howrah bound WAP-4 at Dhubulia railway station]]

== Livery == All WAP-4s are painted in the same red-black with a yellow/cream band livery, though the shade of the red differs from shed to shed, from the blazing crimson red or Green and Yellow (Sapthagiri) of Arakkonam(AJJ)/SR and wam 4 based liveries of Vijayawada(BZA)/SCR to the orange of Erode ED/SR.

== Locomotive sheds ==

{| class="wikitable" |+ !Zone !Shed Name !Code !Quantity |- |rowspan="1" |Central Railway |Bhusaval |BSLL |71 |- |rowspan="2" |Eastern Railway ||Howrah |HWHE |42 |- |Howrah(D) |HWHD |38 |- |rowspan="2" |East Central Railway |Pt. Deen Dayal Upadhyaya |DDUE |11 |- |Samastipur||SPJD||73 |- |rowspan="2"|Northern Railway |Tughlakabad |TKDD |47 |- |Alambagh |AMVD |2 |- |rowspan="1" |North Central Railway |Jhansi |JHSE |38 |- |rowspan="2" |North Eastern Railway |Gorakhpur |GKPL |42 |- |Izzatnagar |IZNE |45 |- |rowspan="2" |Southern Railway |Arakkonam |AJJE |98 |- |Erode(D) |EDDX |71 |- |rowspan="2" |South Coast Railway |Vijayawada |BZAE |38 |- |Guntakal |GTLE |25 |- ||South Eastern Railway |Santragachi |SRCE |60 |- |rowspan="3" |Western Railway |Valsad |BLEE |21 |- |Vatva |VTAD |40 |- |Ratlam |RTMD |10 |- | colspan="3" |'''Total locomotives active as of May 2026<ref>{{Cite web|title=e-Locos|url=http://elocos.railnet.gov.in/Holding/holding.html}}</ref>''' |772 |}

==References==

===Notes=== {{reflist}}

===Bibliography=== {{refbegin}} *{{Hughes-IndianLocos4}} {{refend}}

{{DEFAULTSORT:WAP-4}} Category:Electric locomotives of India Category:25 kV AC locomotives Category:Co-Co locomotives Category:Railway locomotives introduced in 1994 Category:5 ft 6 in gauge locomotives Category:Chittaranjan Locomotive Works locomotives Category:Passenger locomotives