Brushless stator-controlled synchronous-induction machine

It is well known that an induction motor will tend to run at half its normal speed when rotor asymmetry exists in two axes electrically at right angles. Several disadvantages are associated with this mode of operation as compared with a conventional machine wound with twice the number of poles. A means is described, however, by which two such machine elements may be mechanically and electrically coupled so as to eliminate the disadvantages of one machine acting alone. The coupled machine elements may be combined in a single frame in which there may, in some circumstances, be one rotor common to separate stators. This new arrangement can be operated asynchronously, with slip-energy control; or may be run synchronously, with power-factor control. No connections to the rotor are needed in either mode of operation. Experimental work and a theoretical treatment are included.