The application of linear induction motors to conveyors

The principal advantage in using linear induction motors to drive conveyor belts is that force can be applied uniformly to the belt over a wide area without mechanical contact. The drive is therefore independent of the coefficient of friction between belt and rollers and belt stretch is less likely to occur. The main problem in designing a linear motor for such a drive arises from the fact that the speeds required are low, and it is shown that efficient systems are possible only if the motor is supplied with low-frequency power. Two systems are investigated, the first using a woven copper belt and the second a series of solid plates connected to chains along each side. The effect of end-ring resistance and of contact resistance between weft and warp is investigated in the case of the woven belt. The action of the plate conveyor involves the behaviour of discontinuous rotors, and a theoretical investigation of this problem included. The findings are substantiated by experimental results obtained from a fairly large model. Other applications which could utilize the short rotor effect are suggested.