Built by CLW to RDSO specifications, these represent the next indigenous design step up from the WAG-5 locomotives. Used primarily for goods haulage, these locos have a Co-Co wheel arrangement with high-adhesion bogies (shared with WCAG-1, WCAM-3, WDG-2/3A) and Hitachi motors providing 5000hp. Starting TE 402kN (41000kgf); continuous TE 235kN (24000kgf). Adhesion 34.5%. The higher tractive effort compared to the WAG-5 locos allows them to attain higher balancing speeds under load. The first 71 of these all went to the Mughalsarai shed. Kanpur was the second shed to get these locos.
Traction motors are permanently coupled in parallel and speed control is through the use of transformer taps. Max. speed is 100km/h. Air brakes and dynamic (rheostatic) brakes for loco, dual train brakes. MU operation with up to 4 units is possible. Traction equipment such as the smoothing reactor, etc., are all higher rated than in the WAG-5 due to the higher currents this loco draws. Auxiliaries include Rigi compressor, Arno rotary converters, Siemens smoothing reactor, Northey exhauster; other auxiliaries such as blowers from S F India. A number of these locos have been retrofitted with static converters to power the auxiliaries, replacing the older Arno rotary converters. These static converters are more efficient and require less maintenance, besides having self-diagnostic systems to make troubleshooting easier.
These locos too, have limitations similar to the WAG-5 in not being able to start and haul 4500-4700t loads on gradients steeper than 1:200. When they were being designed and introduced, experiments were carried out to vary the gear ratio. The high-adhesion bogies also underwent some modifications for reduction of weight transfer.
The WAG-7H designation is applied to two locomotives of the WAG-7 class that were experimentally modified to provide higher TE by increasing their weight. Oscillation trials were conducted on a ballasted WAG-7 (#27002) around 1995, and then a new WAG-7 loco was built by CLW to have higher weight using thicker plates in the underframe of the loco (#27061, 1995). Weight is 132t, max. TE 441kN (45000 kgf). Traction motors are Hitachi HS15250-G, perhaps a minor variant of HS15250.
[4/04] Newer WAG-7’s have been spotted (e.g., #27455 ‘Samrat’) that externally look somewhat like a WAG-9 and with several improvements such as closed-circuit cameras for monitoring the pantograph and GR, a spotlight to illuminate the pantograph at night, large green lamps to exchange signals on the run, fog lamps, and single-piece windshield. New Katni shed is especially known to add the OHE monitoring equipment to WAG-7 locos. Cabs of some units are air-conditioned. Newer batches of WAG-7’s [12/04] also have data loggers and train parting alarms (based on sensors for detecting loss of brake pressure), as standard equipment. They are also said to have ‘microprocessor control’ although it is not clear what this implies.
- Traction Motors: Hitachi HS15250-G (a variant of the standard HS15250 with higher current rating (thicker wire gauge, better insulation); see description under WAP-4.) Motors built by CLW and BHEL.
- Gear Ratio: 65:18 (65:16?)
- Transformer: CCL India, type CGTT-5400, 5400kVA, 32 taps.
- Rectifiers: Two silicon rectifiers, cell type S18FN350 (from Hind Rectifier), 64 per bridge, 2700A / 1050V per cubicle.
- Axle load: 20.5t
- Bogies: Alco High-Adhesion bogies, fabricated bogie frame assembly, with unidirectional mounting of traction motors, primary and secondary suspension.
- Hauling Capacity: 3010t
- Pantographs: Two Stone India (Calcutta) type AN-12.
- Current Ratings: 1350A/2min, 1200A/10min, 960A/hr, 900A continuous