I found this video of a U23B undergoing a "self load" test.
Questions:
Why do a load test? Is it just to check the generator output, prime mover performance, etc, in the shop?
How does self-loading work? Is there an electrical resistance, like dynamic brake grid, that they cut in to?
Quote:This is the self load testing of the very last General Electric U23B "U-boat" (universal series) locomotive to be built. The location is the Railroad Museum of New England's Thomaston Volunteer Shop.
Load testing a GE U23B U-boat