This paper describes the theory of a tubular linear induction motor (TLIM). The properties of this motor, with its high speed and low moving mass, make it attractive to use as a servo motor for linear mechanical movements. In the paper, a laboratory built TLIM is analysed using the complex phasor method, giving a starting point for the design of a control strategy in the transient mode, while from this analysis, the steady state behaviour is evaluated and compared with measurements. List of symbols a A,, B 4 = slot depth, m D f r F = subscripted forces, N 9 G i I , i, r^ j = J(-1) J , k = subscripted constants L m M n N Ne r current tube, m R = subscripted resistances, V/A T = subscripted time constants, s U, U , 0 = subscripted non-time-dependent voltages, V W = slot width, m x, y, z B,, B, 6, 6, = effective airgap, m, thickness of translator = momentary value for current sheet, A/m = cross-sectional area of conductor in slot, m2 = subscripted flux densities, Vs/m2 = subscripted diameters of TLIM tubes, m = general load friction, N or N s/m = actual airgap length, m = local variable or 'goodness factor' = subscripted momentary currents, A = subscripted non-time-dependent currents, A = total translator mass, kg = subscripted inductances, Vs/A, slot length, m = number of stator phases, region number = subscripted mutual inductances, Vs/A = integer counting number for phases = number of conductors per slot = effective number of conductors per slot = cylinder co-ordinate, m, radius of translator U = subscripted momentary voltages, V = subscripted relative speeds, m/s v = Cartesian co-ordinates, m = slotwidth factors for stator and translator tube, m Paper 7296B (Pl), first 4 = cylinder co-ordinate, rad, airgap flux, V s y = electrical angle between two adjacent phases, rad $ = subscripted flux linkage, V s pLo = permeability of vacuum = 411 x lo-' V s/A m 8 = current turns, A 7 = pole pitch, m col = steady-state frequency for stator voltage or current source, rad/s 1 IntroductionIn mechanical engineering, especially in mechanical automated structures such as industrial robots, fast manipulators and machine tools, linear movements are very usual. Linear speeds up to 10 m/s and displacement accuracies down to 10pm are not uncommon. These movements are mostly obtained by using rotating motors in combination with rotation-to-translation mechanisms. However, in case where high speed and accuracy are required of these mechanisms, serious problems may arise with stiffness, mass, friction and backlash. Obviously a linear actuator will overcome many of these problems. Unfortunately, as with direct drive rotating motors, mechanical fixation of the actuator load in a poweroff situation, such as that obtainable from self braking screw spindle mechanisms is not available. This is a drawback that results from the above-named advantages. A feedback control system, continuously acting during a work cycle of the load, is one possibility that might overcome this problem. The tubular linear induction motor (TLIM) is especially suitabl...
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