Question on Generators and Motors

Question

Would you think that it would be possible to wire a generator to a motor(any kind of motor, dc, ac whatever) to have them work off each other, as in the generator supplies the power to the motor while the motor supplies the torque to the generator? Maybe start the system with a cap or a battery?

Answer 1

Yes. This is often done for testing motors, generators and gears etc. The motor and generator shafts are coupled to each other, perhaps with a transmission or gear in between. Both machines are connected to the utility power source, perhaps through electronic controls. The system can be set up so that the motor produces its rated mechanical power and the generator converts that mechanical power back to electrical power and returns it to the power line. The power line only needs to supply the losses. With this sort of set-up, a 1000 horsepower motor can be tested at full power but only require about 75,000 watts rather than 750,000 watts from the power line.

Answer 2

Energy losses, even the smallest amounts, would defeat this system.  Neither motors nor generators are 100 percent efficient; frictional losses of moving parts and resistive losses in all the wires would cause loss of energy; and since energy is conserved, either this system fails or more energy must be supplied from outside to make up for theses losses.