Train lighting on Indian Railways began with axle-driven dynamos in 1930. Today, four systems remain in use: axle-driven 110V DC, Mid-On-Generation (415V 3-phase generation, 110V AC utilisation), and two End-On-Generation variants (415V and 750V 3-phase generation, both with 110V AC utilisation). New coach construction now standardises on the 110V system.
Axle-Generation System (Self-Generating Coaches)
Each coach generates its own power via a dynamo/brushless alternator driven from the coach axle through flat or V-belts — the coach is electrically independent of its neighbours. All D.C. dynamos have since been replaced by brushless alternators, which are more reliable and need less maintenance since they have no commutator or brushes to wear.
- Alternator ratings in service: 100A (3kW) for MG, 150A (4.5kW) for BG, plus 18kW/130V and 25kW/130V ratings for BG AC coaches.
- The 4.5kW alternator (CGL make) is totally enclosed, develops constant 120V/30V output, and has AC winding + field winding both housed in the stator — the rotor is a toothed 'cogged wheel' with no windings at all, making it inherently brushless.
- Mounting is either 'transom-mounting' (on the bogie — standard for all new 110V coaches) or 'under-frame mounting' (the older style, replaced at POH).
- Two independent safety chains support the alternator to prevent it falling onto the track if the suspension pin breaks.
End-On-Generation (EOG)
For premium, fully air-conditioned services (Rajdhani/Shatabdi-type trains), the connected load is too large for per-coach self-generation — diesel-generator-equipped power cars at each end of the rake feed the entire train instead.
| Coach Type | Count | Load per coach (KW) | Total (KW) |
|---|---|---|---|
| AC 3-Tier | 8 | 40.00 | 320.00 |
| AC 2-Tier | 6 | 34.75 | 208.50 |
| AC First | 1 | 15.75 | 15.75 |
| AC Pantry | 2 | 76.75 | 153.50 |
| AC Power Car (working) | 2 | 49.00 | 98.00 |
This real Rajdhani rake example (Mumbai Central–New Delhi) totals ~800 KW connected load across 19 coaches. Applying a diversity factor of 0.7, maximum demand works out to 560 KW.
- Two feeders run the length of the rake via inter-vehicular (I.V.) couplers; each coach has its own control/distribution/feeder-changeover panel.
- Emergency lights in the power cars switch on automatically via a No-Volt contactor if main supply interrupts.
- 500 KVA alternators are used (though the calculated requirement is ~350 KVA) to accommodate future load growth, de-rating factors, and load imbalance.
- Two diesel engine makes are used for 750V power cars: Kirloskar Cummins KTA-1150G (450 BHP at 38°C) coupled to KEC alternators, and INTACH 3406B (398 BHP at 55°C) coupled to KEL alternators.