A brushless variable-speed induction motor

A conducting sheet threaded by a magnetic field moving parallel to the sheet will assume a velocity equal to that of the field if it is free to move. The squirrel-cage induction motor uses this principle. The research described in the paper was initiated to discover what would occur if the sheet were constrained so that it could move only in its own plane and in a direction making an angle with the direction of motion of the field. It is found that, under certain circumstances, the sheet then travels at a speed in excess of the speed of the field. This phenomenon has been made the basis of a variable-speed brushless induction motor.