Double differential, electrically compensated constant speed drive

A constant speed drive for developing constant speed motive power from variable speed motive power developed by a prime mover, comprising:

• first and second differentials each having first and second inputs and an output, the differential outputs being coupled together and producing the constant speed motive power, the first input of the first and second differentials being coupled through gear sets to the output of the prime mover whereby the first input of the first differential is driven at a speed greater than a desired output speed of the drive and the first input of the second differential is driven at a speed less than the desired output speed;
• a first permanent magnet machine having a motive power shaft coupled to the second input of the first differential, the first permanent magnet machine being driven as a generator to develop alternating current power at power windings thereof;
• a second permanent magnet machine having a motive power shaft coupled to the second input of the second differential, the second permanent magnet machine including electrical power windings;
• a rectifier circuit connected to the power windings of the first permanent magnet machine for rectifying the power developed by such machine to derive intermediate DC power;
• a DC/DC converter coupled to the rectifier circuit;
• an inverter coupled between the DC/DC converter and the power windings of the second permanent magnet machine;
• and
• means for controlling the DC/DC converter and the inverter so that the second permanent magnet machine develops compensating speed of appropriate magnitude to cause the output of the second differential to develop motive power at the desired speed.