I have been using power cable from the old MD-3 power units for the last 45 to 50 years.
MD-3 GROUND POWER UNIT
Posted 1/21/2009 Printable Fact Sheet
Photos
DAYTON, Ohio - MD-3 Ground Power Unit in the Cold War Gallery at the National Museum of the U.S. Air Force. (U.S. Air Force photo)
This unit was designed to provide 28-volt DC 1500 amp, 115/220-volt AC three-phase electrical power for B-47 aircraft for ground operation and start. It also can be used with other aircraft (such as the T-33) that have power requirements compatible with its output. It uses a Continental 180-hp six-cylinder reciprocating engine to drive its electrical generators.
The unit was restored for the museum by the 4950th Field Maintenance Squadron, Wright-Patterson Air Force Base, Ohio, in 1979-1980.