Direct Current

One day in 1964 a new navy guy reported aboard, moved into the living quarters, plugged in his electric toothbrush and went up to dinner. Upon returning he found his stateroom full of smoke and the nasty odor of an electrical fire. The electric toothbrush had undergone a DC meltdown. It was history.

In 1944 Michelson was built, as SS Joliet Victory, with a 110/220 volt DC (direct current) ship's service power system. Michelson's pumps, hoists, fans and lifeboat winches all ran on DC. Even the mixer in the galley. When converted to a survey ship DC outlets were wired into the newly created living spaces as well. Anything with a "universal motor" would run just fine on DC, but not for devices containing a transformer.

The DC electric outlet our newbie sailor used was above the sink, intended for electric shavers.

Use of direct current was common on old ships including passenger ships built through the 1950s, long after most of the world had gone to AC (alternating current).  

 Oddly, some other ships of the same WW II vintage were built with AC ship's service power. The once ubiquitous T-2 tankers were all AC, including propulsion, with steam turbine driving a alternator and three phase motor turning the propeller shaft. Reverse direction involved switching two of the motor phase leads.

Motor-Generator Set

Meanwhile, our electronic stuff supporting survey operations demanded AC, not DC. The ship's chief electrician had an electrical shop on the deck below our living quarters. Here there were three 600 volt DC to 120/240 volt AC motor-generator sets creating all the AC needed, with two of three MG sets running all the time. These supplied power to the technical load. An additional 300 kw turbo generator in the engine room supplied 120/240 volt AC power for the ship's lighting and other domestic needs.

There was AC available in the living quarters, but you had to know where to find it. Our electric toothbrush guy didn't know enough to ask.