text: FIG. 7 is a schematic diagram of a controlled variable impedance for use in the adaptive regulator illustrated in FIGS. 1 or 3.
  FIG. 8 is a schematic diagram of more details of the load sensor and switching logic portion of the circuit illustrated in FIG. 3.
  In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word connected or terms similar thereto are often used. They are not limited to direct connection but include connection through other circuit elements where such connection is recognized as being equivalent by those skilled in the art.
  FIG. 1 illustrates a free piston Stirling engine 10 mechanically linked to drive an alternator 12 which incudes field magnets 14 which are driven in reciprocation by the engine 10. The alternator 12 has an armature circuit 16 which includes a conventional, series compensating capacitor and which is connected to a useful load 18. The free piston Stirling engine, its heat energy source and the alternator, as above described, may be of the conventional type previously known in the art.
  The invention as illustrated in FIG. 1 has a controllably variable conductance G1 which is shunted across the armature 16 parallel to the useful load 18. The conductance G1 is preferably an electronic circuit equivalent to a variable resistive load, having a variable conductance which is varied and controlled by a feedback control circuit. The variable conductance G1 may, for example, consist of the simple circuit illustrated in FIG. 7 in which the impedance Z3 and the emitter impedance Z4 are series connected by transistors T1 and T2 to form the variable load. The effective impedance of the transistors T1 and T2 is controlled by the output applied to their base and each conducts on opposite half cycles of the alternator output voltage.