A Contribution to the Theory of the Deep-Bar Induction Motor

The deep-bar rotor may be defined as a single-cage rotor in which skin effect plays a prominent part. With rotor slots nearly one inch deep, skin effect reduces starting current and increases starting torque so that in many ratings this type of motor has superseded the older shallow cage motor. This paper will endeavor to supply the theory of the tapered bar and of bars with a tapered section.It also will endeavor to improve the theory of the round bar. A graphical method for computing the impedance of any shape of bar will be given.The formulas developed indicate that further improvements should result if the bar is somewhat enlarged near the slot opening.It will be hown that: 1) The tapered bar is superior to the rectangular bar, provided the narrow portion is near the top. 2) Further improvements should be sought among bars of compound shape. 3)The slot constant,for a round slot is close to 0.72when running.