Levitation Performance of Two Opposed Permanent Magnet Pole-Pair Separated Conical Bearingless Motors

In standard motor applications, rotor suspension with traditional mechanical bearings represents the most economical solution. However, in certain high performance applications, rotor suspension without contacting bearings is either required or highly beneficial. Examples include applications requiring very high speed or extreme environment operation, or with limited access for maintenance. This paper expands upon a novel bearingless motor concept, in which two motors with opposing conical air-gaps are used to achieve full five-axis levitation and rotation of the rotor. Force in this motor is created by deliberately leaving the motor s pole-pairs unconnected, which allows the creation of different d-axis flux in each pole pair. This flux imbalance is used to create lateral force. This approach is different than previous bearingless motor designs, which require separate windings for levitation and rotation. This paper examines the predicted and achieved suspension performance of a fully levitated prototype bearingless system

Performance analysis of suspension force and torque in an IBPMSM with V-Shaped PMs for flywheel batteries

© 1965-2012 IEEE. Due to the advantages such as high energy density, high power density, high cyclic life, and environmentally friendly, the flywheel battery has the potential to solve the problem of energy storage. In order to improve the torque density and suspension performance of bearingless synchronous permanent magnet (PM) synchronous motors (BPMSMs), a novel rotor structure with V-shaped PMs is designed in this paper. Furthermore, the interior BPMSM (IBPMSM) with V-shaped PM which used for flywheel batteries of electric vehicles is researched in detail. Especially, the influence of geometrical parameters of V-shaped PM on suspension force and electromagnetic torque is investigated. Moreover, the corresponding static electrical magnetic characteristics including inductances and electromagnetic torque are also studied. The finite-element method is employed to evaluate the theoretical analysis of the proposed IBPMSM. In addition, the optimized motor is validated to have good suspension performance by some experiments

Assessment of Technologies for Noncryogenic Hybrid Electric Propulsion

The Subsonic Fixed Wing Project of NASA's Fundamental Aeronautics Program is researching aircraft propulsion technologies that will lower noise, emissions, and fuel burn. One promising technology is noncryogenic electric propulsion, which could be either hybrid electric propulsion or turboelectric propulsion. Reducing dependence on the turbine engine would certainly reduce emissions. However, the weight of the electricmotor- related components that would have to be added would adversely impact the benefits of the smaller turbine engine. Therefore, research needs to be done to improve component efficiencies and reduce component weights. This study projects technology improvements expected in the next 15 and 30 years, including motor-related technologies, power electronics, and energy-storage-related technologies. Motor efficiency and power density could be increased through the use of better conductors, insulators, magnets, bearings, structural materials, and thermal management. Energy storage could be accomplished through batteries, flywheels, or supercapacitors, all of which expect significant energy density growth over the next few decades. A first-order approximation of the cumulative effect of each technology improvement shows that motor power density could be improved from 3 hp/lb, the state of the art, to 8 hp/lb in 15 years and 16 hp/lb in 30 years

Model-Based Levitation Control of A 100 kW Bearingless Electric Motor

The use of magnetically levitated rotors for various applications, especially in pumps and compressors, has seen an unprecedented rise in the last few years. Bearingless motors combine levitation and torque production capabilities. They offer more compact footprint and require less power electronics compared to more traditional active magnetic bearing supported motors. A lot of significance has been attached to reducing cost, complexity and broadening applicability of the magnetically levitated rotors. Hence, the levitation control of rotors in such bearingless machines has become quite an interesting topic of research. Digital control strategies need to be adopted for proper levitation control of rotors. Furthermore, it has to be kept in mind that these rotors cannot afford to have too many oscillations under different environmental conditions because oscillations can eventually lead to instability and heavy losses. This thesis presents a state-of-the-art model-based digital control of the levitation of a 100 kW bearingless electric motor where the point-mass of the rotor is considered. This motor has a rated speed of 22000 rpm. The entire bearingless motor system is converted into state-space models by taking into account the bearingless machine's nominal operating points and conditions. Then, a model-based controller with Pincer's conditions, coupled with an estimator with Kalman filtering, integral action and state-command path, is implemented and tested for the levitation control. FEM derived Simulink model of the bearingless motor is tested to verify the proposed control strategies. The closed-loop poles and zeroes, step responses of the closed-loop system and the frequency responses are also recorded from the simulations. In the end, the control of the rotor is investigated with five different combinations involving controller, estimator, integrator and state-command path. Comparisons are conducted on the the proposed control strategies and conclusions are drawn based on the findings

Position control study of a bearingless multi-sector permanent magnet machine

Bearingless motors combine in the same structure the characteristics of conventional motors and magnetic bearings. Traditional bearingless machines rely on two independent sets of winding for suspension force and torque production, respectively. The proposed Multi-Sector Permanent Magnet (MSPM) motor exploits the spatial distribution of the multi-three-phase windings within the stator circumference in order to produce a controllable suspension force. Therefore, force and torque generation are embedded in the same winding setting. In this paper the force and torque generation principles are investigated and a mathematical model is presented considering the rotor displacement. A two Degree of freedom (DOF) position controller is designed taking into consideration the rotor overall dynamic system and a controller gains selection strategy is suggested. A simulation study of the bearingless system in different operating conditions is presented and the suspension force and torque produced are validated through Finite Element Analysis (FEA)

Radial force control of multi-sector permanent magnet machines for vibration suppression

Radial force control in electrical machines has been widely investigated for a variety of bearingless machines, as well as for the conventional structures featuring mechanical bearings. This paper takes advantage of the spatial distribution of the winding sets within the stator structure in a multisector permanent-magnet (MSPM) machine toward achieving a controllable radial force. An alternative force control technique for MSPM machines is presented. The mathematical model of the machine and the theoretical investigation of the force production principle are provided. A novel force control methodology based on the minimization of the copper losses is described and adopted to calculate the d–q axis current references. The predicted performances of the considered machine are benchmarked against finite-element analysis. The experimental validation of the proposed control strategy is presented, focusing on the suppression of selected vibration frequencies for different rotational speeds

Parameter matching and structure optimal design of a brushless DC motor for a battery electric vehicle

© 2017 IEEE. Calculation and matching of the main parameters of a brushless DC (BLDC) motor for a Battery electric vehicle (EV) is studied in this paper. Usually, different shapes of permanent magnet (PM) and different magnetizing methods will affect the performance of the motor. Especially when the motor is designed for an EV, more elements need to be considered, such as efficiency under normal operating conditions and torque ripple. So in this paper the performance of PMs with different shapes and different magnetizing methods will be compared by finite element analysis (FEA). Finally, the structure of the stator and rotor will also be optimized to obtain the required prototype model

Performance improvement of bearingless multi-sector PMSM with optimal robust position control

Bearingless machines are relatively new devices that consent to suspend and spin the rotor at the same time. They commonly rely on two independent sets of three-phase windings to achieve a decoupled torque and suspension force control. Instead, the winding structure of the proposed multi-sector permanent magnet (MSPM) bearingless machine permits to combine the force and torque generation in the same three-phase winding. In this paper the theoretical principles for the torque and suspension force generation are described and a reference current calculation strategy is provided. Then, a robust optimal position controller is synthesized. A Multiple Resonant Controller (MRC) is then integrated in the control scheme in order to suppress the position oscillations due to different periodic force disturbances and enhance the levitation performance. The Linear-Quadratic Regulator (LQR) combined with the Linear Matrix Inequalities (LMI) theory have been used to obtain the optimal controller gains that guarantee a good system robustness. Simulation and experimental results will be presented to validate the proposed position controller with a prototype bearingless MSPM machine