Indian Railways class WCAM-1

The WCAM-1 was India's first dual-voltage locomotive when it was introduced in 1973. The designation stood for broad gauge (W), DC Current (C), AC Current (A), Mixed traffic (M) and 1st generation (1). It had been ordered to provide services across the 1,500 V DC lines in the suburbs of Mumbai and the 25,000 V AC mainlines in the area and was based on the WAM-4. Although designed as a mixed-traffic locomotive with a top speed of 120 km/h, it was mostly used for passenger trains. 53 had been built by Chittaranjan Locomotive Works until 1979.

The transformer had a fixed ratio so that the power from the AC line was always converted to 1,500 V and being fed into silicon rectifiers. Finally, power control was always done by placing the traction motors in series, series-parallel and parallel, by resistors and by using weak field. However, the locomotive could only reach 100 km/h in DC mode and its continuous output was limited to 1,753 kW, compared to 2,714 kW in AC mode. It is being stated that these locomotives were robust in general, but were hard to operate, with fusible links which did melt quite often. After the arrival of new locomotives in the late nineties, the WCAM-1 was soon only used with light passenger trains. They were withdrawn in 2015 when all DC stretches in the Mumbai area had been converted to AC.