IOC No. 511, a GMD SW1200MG.

(IOC, W. Lenheim Collection)



The GMD SW1200MG is a 4-axle electric locomotive built by General Motors Diesel between 1963 and 1971. The locomotive is the electric version of the diesel powered SW1200, with the prime mover replaced by a motor-generator set, hence the MG suffix in the model number.

Locomotives run under 2400V 60 Hz, in automatic control without driver. The difference with SW1200 is that a single-phase electric motor is provided in place of the diesel engine, with adapted control.

Nine examples of this locomotive were built for a single Canadian customer – Iron Ore Company of Canada (IOC).


A diagram of the GMD SW1200MG.

(IOC, W. Lenheim Collection)


Autonomous railway system

As of 2019, IOC's Carol Lake mine near Labrador City, Labrador utilizes a small fleet of GMD SW1200MG electric locomotives to haul raw ore from the mine to a processing plant. The short electrified railway is the last remaining electrified cargo railway in Canada.

The cargo trains are unmanned and fully automated, advancing block by block based on the condition of the block of track ahead. The motive power is SW1200 MG single units, each having a single phase AC motor driving the standard EMD traction generator and traction motors. A horn blows every few seconds as a constant warning that the trains are unmanned.