Let's assume we have a motor (prime mover) or an array of motors, and this motor(s) is driving an array of generators.  The motor will generate a BEMF working against our applied EMF.  We'll use this BEMF in our motor to achieve Negative Resistance & Negative Inertia.  I know, at first this appears to be counter intuitive.  Next, we must reverse the EMF generated in our array of generators where it is working with the applied EMF of the motor while torquing the motor in the forward direction (I'll explain how to accomplish this later, but it should be clear how to do this, once you understand the following process).  Here is the process:

1.)  As the motor and generators increase in speed, then the BEMF of the motor becomes stronger.  As the BEMF increases, then our applied current decreases.  Once we reach a critical speed where our applied EMF and the BEMF of the motor are equal and opposite in strength, then we will reach unity (minus bearing friction, air drag, etc.).  At this point, it is very similar to a motor idling without a load.  Also note, the induced magnetic field in the motor will be canceled, but the induced magnetic field in the generators will be equal in strength and in opposition to the applied magnetic field.

2.) As the array of generators is torquing the prime mover in the forward direction, then the speed will continue to increase (there is a limit, and this limit will be explained).  As the speed continues to increase, then the BEMF of the motor will become stronger than the applied EMF and we will have negative energy charging our battery.  When this occurs, then we have reached OU & Negative Resistance.  After reaching negative resistance, then the polarity of the induced magnetic field in the motor will reverse and will no longer be in opposition to the applied magnetic field and will provide a Negative Inertia, and the induced magnetic field of the generators will be stronger than the applied magnetic field while increasing it's Positive Inertia.

3.) The speed limit will be reached when the Negative Inertia and Positive Inertia becomes equal in strength.  We can increase this limit by adding more motors and generators and by increasing the strength of the applied magnetic field.  If we used electromagnets instead of permanent magnets as our applied field, then we can in theory feed the excess energy back into the electromagnets to increase the applied field and have no speed limit.

Gravock