Layout: what is where

Tap any block for what it does and what replaced it on the other loco. Tap a WAP7 traction converter to open the cabinet. Both are 25 kV AC locos; the WAP7 is shown with its IGBT propulsion. The drawings are schematics: the transformer and converter placement and the cabinet contents come from IR and Hind Rectifiers documents, but the order of the smaller cubicles along the floor is approximate.

Traction power path Auxiliary supply Control Air and brakes Cooling Coach (hotel) power Under the floor or on the roof

WAP4 · tap changer

DC motors · plan

WAP7 · three-phase

AC motors · plan

Dashed outlines are on the roof or under the floor. For those levels, see the side views on Power flow.

Where to see real photos

IRFCA: Inside WAP4 by Zubin Dotivala. Captioned photos of the smoothing reactors, transformer oil pump, tap-changer contactor with its transition resistors, line and reverser contactors, the DJ breaker, battery charger and the interlock key box. The same page links his WAG7 interior set, which is the WAP4's freight sibling.
CLW / Hind Rectifiers IGBT propulsion manual (PDF). The cabinet drawing on this page follows its figures 4.9 and 4.10. Pages 48–75 show the SR cubicle front and rear, the IGBT power units, the crowbar resistor, coolant pump and power terminals; chapter 3 shows the VCU rack inside SB1/SB2.
IRIMEE: Introduction to Electric Locomotive (PDF). Ratings for the tap-changer loco's transformer, rectifier, smoothing reactor and HS15250A motors, and the regen comparison.
IRFCA photo gallery: electric locomotives. Browse the WAP7, WAG9 and WAP5 albums; shed open days and workshop visits sometimes include machine-room shots.
Video: search YouTube for WAP7 machine room or WAG9 engine room walkthrough. Crew and shed vloggers often walk both aisles with the converter doors closed.