I'm writing simulation software for a civilian helicopter.
The helicopter has two engines and two generators.
Normally, we calculate the amperage reading of a generator through Ohms.
I = W / V.
However, there is a venting switch on the overhead panel, that "vents" a particular engine. From what I've read, this also enables a starter relay, and I've been told that it is similar to "spinning up a generator without actually starting the generator."
By observing videos from the actual craft, venting an engine immediately drops the corresponding generator amperage from 0 to -270.
I do not know enough about electrical engineering or automotives to explain why this happens.
Why does the generator drop to a negative amperage?
Is the engine somehow providing a negative load to the generator?
Image shows an arrow to the venting engine.
The negative amperage of the generator is circled.