Dual compartment-temperature refrigerator with positive internal air circulation

Claim 1

In a refrigerator of the type including two compartments having separate access doors and operated at substantially different temperatures but having fluid communication therebetween, an evaporator located in one of said compartments for circulation of refrigerants through said evaporator a fan within said one compartment for positive circulation of air over said evaporator and through said compartments, the improvement which comprises: a variable speed brushless D. C. motor for driving said fan, said motor consisting within said one compartment of a permanent magnet rotor connected to said fan, a disc on the shaft of said rotor, a pair of stationary position detecting coils adjacent said disc and the stationary y-connected winding surrounding said rotor; and exterior of said compartment, a rotor position sensing circuit connected to said position detecting coils, a commutation circuit connected to said armature winding, and a circuit connected to said armature winding for detecting and controlling the speed of said motor; said speed control circuit being a constant voltage type having a first transistor constituting a detecting section for detecting variations in the source voltage between its base and emitter, a second transistor constituting a comparing section for comparing its collector current with a reference voltage, and a third transistor constituting a controlling section controlled by variations in output, particularly those in the collector current of the second transistor so as to control exciting current supplied to the system with which said speed control circuit is associated, said first, second and third transistors being connected in series; whereby the rotation of said motor is controlled and the speed maintained with a minimum of heat transfer to said compartments.