a form of electro-mechanical conservation given by (15) this is arrived at starting from a mechanical conservation (5), then upon consideration of Kirchoff's voltage law we are able to establish a system of differential equations (7) and (13), combined altogether to get the overall electro-mechanical conservation (15)
https://foxtrotpaparomeo.wordpress.com/2023/05/06/06052023electro-mechanical-conservation-laws-in-the-dynamics-of-an-electric-motor/