Linear Machines for Long Stroke Applications—A Review <s> VII. QUALITATIVE COMPARISON OF LINEAR PRIMARY PM MACHINES <s> A novel partitioned stator flux reversal permanent magnet (PS-FRPM) linear machine with segmented iron mover is introduced. The operation principle of the PS-FRPM linear machine is described, and the optimisation of the machine leading design parameters for maximum thrust force using genetic algorithm has been carried out. Moreover, in order to investigate the longitudinal end effect on the machine performance a periodic model has been employed to compare with the real model. It is found that the end effect has a significant impact on the machine performance, particularly in terms of unbalanced magnetic circuit and cogging force. Additionally, the influence of the mover iron pole numbers on the electromagnetic performance of PS-FRPM linear machines has been examined, i.e. 6/4, 6/5, 6/7, 6/8, 6/10 and 6/11 stator/mover pole combinations are designed and compared. It is concluded that the machine with a mover pole pitch which is closer to the stator slot pitch exhibits the best performance among the others. <s> BIB001 </s> Linear Machines for Long Stroke Applications—A Review <s> VII. QUALITATIVE COMPARISON OF LINEAR PRIMARY PM MACHINES <s> In this paper, a transverse-flux flux-reversal linear motor (TF-FRLM) is proposed. With magnets on the primary side, the proposed motor is suitable for long-stroke application, benefiting from easy manufacturing and low-cost secondary cores. First, the basic structure and operating principle of the proposed motor are presented. Then, the expressions of back electromotive force (EMF) and electromagnetic thrust are obtained by an equivalent magnetic circuit model. Third, for saving computation time, a simplified half-phase model with a symmetry boundary is employed in the 3-D finite-element analysis (FEA) to investigate the TF-FRLM, and the field distribution, the back EMF, the detent force, as well as the thrust force are emphasized. Finally, a prototype is constructed, and experiments show good agreement with the FEA results. <s> BIB002 </s> Linear Machines for Long Stroke Applications—A Review <s> VII. QUALITATIVE COMPARISON OF LINEAR PRIMARY PM MACHINES <s> Linear flux-reversal permanent magnet machines (LFRPMs) have attracted increasing attentions in recent years due to its excellent performances, such as high efficiency, superior acceleration characteristics and simple maintenance [1]. <s> BIB003 </s> Linear Machines for Long Stroke Applications—A Review <s> VII. QUALITATIVE COMPARISON OF LINEAR PRIMARY PM MACHINES <s> This paper proposes a new flux concentrated version of a consequent pole linear Vernier hybrid permanent magnet machine. The Vernier hybrid machine stator has alternatively magnetised adjacent magnets directly in contact with each other. A salient rotor then switches the direction of flux past the stator coils. Alternate magnets can be removed to make the consequent pole version, where inset rectangular magnets are magnetized in a common direction and separated by soft magnetic poles. In a flux concentrated consequent pole configuration, each magnet pole comprises of two magnets forming a V -shape. This topology hence possesses a combination of consequent poles, flux concentration and flux switching machine topologies. Magnetic flux concentration increases the airgap flux density, which potentially leads to an improvement of the force density and operating power factor. This paper compares the inset and V -shape consequent pole topologies using finite element analysis simulations. Both machines have the same dimensions, magnet volume, rated speed and current density. The simulation results imply that the V-shape machine offers higher electromagnetic performance. To confirm this, two linear prototypes are currently under construction, where the key parts that already produced are presented in this paper. <s> BIB004
In order to fulfil both cost and high energetic efficiency requirements, modern drive systems must adopt highly efficient actuators which can be reasonably cost effective in terms of the required materials and the manufacturing process. In this section, a qualitative comparison table is given. The table is based on the literature research. The table serves as a summary of the capabilities of LPPMs, to allow designers to select the ideal topology for a given list of requirements. Thrust density, shear stress, thrust per PM volume, detent force, thrust ripple and PM immunity are discussed in this section. Typical values for the design parameters like the linear loading, current density, or magnet remanence are within the same range for all the types of machines, with of 20-35 kA/m, 3.5-7.5 A/mm 2 , and 1.2-1.35 T respectively. As discussed in the previous section, the power factor is very low for LVPMs, and although it has not been analysed as much for LFRPMs, the same performance could be deduced from their RM counterparts. No references to the power factor of doubly-salient machines have been found in the literature, so this characteristic is left out of the table. However, as a general reference, LVPMs show power factor values ranging from 0.3 to 0.6, and the range for LSFPMs in the literature is 0.7-0.85. For LDSPMs, as mentioned before, there are not many mentions in the literature, but the machines that have been found can generate ∼100 kN/m 3 , with a shear stress range of 6.4-10.7 kN/m 2 . Regarding PM usage, these machines generate 3.6-7 MN/m 3 . The detent force and thrust ripple of these machines are also quite high, especially for the basic configuration, with 35-50 % detent force and 40-55 % thrust ripple. However, applying skew or a modular configuration this values can be reduced to 8.5-16.5 % and 12-15 %. As for PM immunity, LDSPMs are said to have an excellent demagnetisation withstand capability. In case of LFRPMs, the thrust density range is much larger due to the partitioned-primary configuration BIB001 . This machine, with 560 kN/ 3 can generate much higher thrust force than the other configurations in the literature, generally ranging around 150-200 kN/m 3 . The shear stress of LFRPMs is generally found to be around 7-8 kN/m 2 , and the magnet usage is also quite good, with values of 5-8 MN/m 3 . In this case, the thrust capability per PM volume of large slotopening LFRPM machines is calculated to be of 11.5 MN/m 3 BIB003 , only surpassed by the 19.6 MN/m 3 generated by the partitioned-primary LFRPM. Detent and thrust forces are generally lower than in the case of LDSPMs. In both cases, 5-10 % values are often found in the literature. The main drawback of LFRPMs comes when analysing their PM immunity, with an inherently low resistance against PM demagnetisation BIB002 ,  . The thrust density of LSFPMs has been found to range around 300-500 kN/m 3 depending on the selected structure. The shear stress usually ranges ∼10-13 kN/m 2 , and ripple factors lower than 5 % are rarely found in the literature, with a typical range of 8-15 %. Although the PM demagnetisation immunity is great for the LSFPMs, due to their problematic flux leakage, they generally produce ∼2.5-4 MN/m 3 of PM volume. In these aspect, both E-core and C-Core machines can produce ∼7 MN/m 3 , thus considerably reducing the cost of the active part of the machine. Finally, the shear stress that can be generated by vernier machines is off the charts. The most common values that have been found in the literature range between 20-50 kN/m 2 , with reported values as high as 70 kN/m 2 BIB004 . Thrust density-wise, LVPMs are comparable to LSFPMs with 250-400 kN/m 3 . The PM usage is also great with these machines, with commonly found values of 9-15 MN/m 3 of magnet volume. Another great advantage of LVPMs are the low values of detent force and thrust ripple that they normally exhibit. These can normally be found to be ∼5 % for LVHM machines, or even lower for LPPMVMs. The main disadvantages of these machines are the low power factor and the weak PM immunity.