Linear Motors With The Ladder-Slot Arrangement In The Non-Ferromagnetic Movers

Linear motors(LMs)are widely used in high-speed applications such as: the railway transportation,the electromagnetic launch system,the industrial utilizations and machines,among which the railway transportation and the electromagnetic launch require further development and innovations of the high-speed LMs.This dissertation proposes the LMs with the ladder-slot arrangement in the non-ferromagnetic mover as a novel topology for high-speed drives.A theoretical model is established,and then theoretical calculation and optimization are accomplished to analyse the effect of the ladder-slot arrangement on the LMs.To establish the general theory,as the ladder-slot arrangement is inserted into the non-ferromagnetic mover,the corresponding electromagnetic field is analysed as the first step of modelling the linear motor.The longitudinal end effect of the ladder-slot mover is therefore derived via partial differential equations in ladders and slots.And the parameters with the second type of longitudinal end effect are theoretically calculated in terms of the geometries of the ladder-slot non-ferromagnetic mover,which provides a mathematical foundation for the design and analysis of this novel type of LMs.Then considering the application of variable-pole-pitch(VPP)propulsion,the non-ferromagnetic mover with the ladder-slot arrangement is applied to the linear induction motor(LIM)and the permanent magnet linear synchronous motor(PMLSM):The equivalent circuit of the ladder-slot mover doubled-sided linear induction motor(LS-DLIM)is established with the longitudinal end effect of the ladder-slot mover considered.The asynchronous steady-state performances,including the power factor and the thrust,are calculated in terms of the slip of mover speed.With the theoretical calculation,the LS-DLIM aces in eliminating the transversal end effect and enhancing the power factor compared with its counterpart of a solid version.The line-start PMLSM applied to the VPP propulsion is proposed in the dissertation for the first time to the best of our knowledge,in which the ladder-slot arrangement is combined with the PM material.The model for transient analysis is built up with the harmonics of the permanent magnet flux linkage.Meanwhile,the impedance matrix is built up with the coefficient of the ladder-slot-arrangement longitudinal end effect.Transient characteristics during the line-start process are estimated theoretically after a reasonable step is selected.Compared with the conventional version,the ladder-slot arrangement in the mover enhances the asynchronous-start capability of the PMLSM and makes the VPP starting driven by the PMLSM feasible.Therefore,the VPP propulsion driven by the non-ferromagnetic mover LMs with the ladder-slot arrangement is optimized,which is based on sectional simplification calculated with the aforementioned model and analysis.Both the requirements of the electromagnetic launch system and the laws to design the ladder-slot mover LM are taken into account as the constraints.Hence,the structure optimization of the VPP propulsion is described as a non-linear mathematic model.And the optimal solution to this varied-dimension model is achieved with the partial swarm optimization.To make the non-ferromagnetic mover with the ladder-slot arrangement finally operate at a constant speed after asynchronous start,the direct thrust and flux control(DTFC)is studied to drive the line-start PMLSM according to the model proposed above.The theoretical models of the LS-DLIM and the line-start PMLSM with the ladder-slot arrangement,as well as corresponding analysis on their characteristics is validated on the hardware setup of the small-scale prototype.Both the theory of the LMs with the ladder-slot non-ferromagnetic and the optimization in high-speed propulsion are proved effective.The major contribution of this research is a novel topology and optimization with the ladder-slot arrangement in the non-ferromagnetic mover that can be applied to high-speed LM drives.