Efficiency and cost-effectiveness comparison between synchronous reluctance motor and induction motor

Abstract

It is well-known that the induction motor(IM) is the workhouse of industry due to its ruggedness, low cost and good performance. In recent decades, the developments in power electronics and digital control have triggered the wide speed usage of IMs for variable speed drives in motor industries. But the higher efficiency performance and more cost-effectiveness demands of motor are always attractive. Recent years, the synchronous reluctance motors(SynRM) are considered as good candidate to the IMs in the industry application due to excellent characteristics, such as: lower maintenance cost from reducing mechanical parts, get the performance of permanent magnet(PM) motors without use of magnets, eliminate rotor cage losses of induction motor to increase motor efficiency, adjust rotation speed for energy saving by inverter control, which suggests that the SynRM can be widely used in all industrial application, such as pump, fans and compressors etc. Different from the IM depending on the induced magnetic torque produced by the cages bars, the SynRM utilizes the reluctance torque generated by the multilayer flux barriers in the rotor, which avoids the copper losses and decrease the cost of materials. A series of IE4-class SynRM product has been developed by our engineers with output power from 0.27kW to 45kW based on our mature IE3 IM products. In this paper, a few of SynRM product are presented for comparison with their corresponded IM products, that their efficiency performance are measured to verify their efficiency satisfies the IEC super premium efficiency level (IE4-class), which means the SynRM have at least 15% losses reduction compare to its corresponded IE3-class IMs. The higher efficiency is achieved by the optimal shape design of the multi-layer barriers in SynRM rotor, as well as balancing the copper loss and iron losses properly. The cost-effectiveness feature is emphasized that the SynRM can reduce of the amount of active magnetic materials both of copper coil and iron sheet, as well as eliminating the cages bars (Aluminium) of IM. In this paper, the presented IE4-class SynRM can effectively reduce the cost including the materials cost compare to the identical power IE3-class IM, which highly increases the cost competition of product in industrial electric machine market. In conclude, the SynRM product can be an attractive solution for higher efficiency and more cost-effective as the industry required.