Browsing by Subject "torque"

Now showing 1 - 9 of 9

Chiral symmetry breaking for deterministic switching of perpendicular magnetization by spin-orbit torque
(2020-12-18) Wu, Hao; Nance, John; Razavi, Seyed Armin; Lujan, David; Dai, Bingqian; Liu, Yuxiang; He, Haoran; Cui, Baoshan; Wu, Di; Wong, Kin; Sobotkiewich, Kemal; Li, Xiaoqin; Carman, Gregory P.; Wang, Kang L.
Symmetry breaking is a characteristic to determine which branch of a bifurcation system follows upon crossing a critical point. Specifically, in spin-orbit torque (SOT) devices, a fundamental question arises: how to break the symmetry of the perpendicular magnetic moment by the in-plane spin polarization? Here, we show that the chiral symmetry breaking by the antisymmetric Dzyaloshinskii–Moriya interaction (DMI) can induce the deterministic SOT switching of the perpendicular magnetization. By introducing a gradient of saturation magnetization or magnetic anisotropy, non- collinear spin textures are formed by the gradient of effective SOT strength, and thus the chiral symmetry of the SOT-induced spin textures is broken by the DMI, resulting in the deterministic magnetization switching. We introduce a strategy to induce an out- of-plane (z) gradient of magnetic properties, as a practical solution for the wafer-scale manufacture of SOT devices.
Comparison of the Nature of Torque Production in Reluctance and Induction Motors
(IEEE, 1990-06) Hsu, J. S.; Liou, S. P.; Woodson, H. H.
The nature of torque production is different in reluctance and inductance motors. One significant difference occurs in a reluctance motor that has nonsalient stator punching and a salient motor. When the flux per pole is small in such a motor, the torque can still be high, as long as the rate of energy change with respect to the rotor angular displacement at the rotor pole fronts and pole ends is high. A theoretical foundation to improve the torque capability of reluctance motors is provided. Effects of saturation and stray-load loss are also studied. Experimental results show agreement with theoretical conclusions
Flywheel Batteries for Vehicles
(2002-06) Beno, J.H.; Thompson, R.C; Hebner, R.E.
Energy storage flywheels are useful in power conditioning applications, i.e. when there is a mismatch between the power generated and the power required by the load. Two examples of this mismatch are a temporal mismatch and a mismatch in magnitude. The use of a flywheel in a hybrid vehicle, for example, permits the engine to be designed to provide only the power needed to overcome steadystate losses and not have the inefficiencies that result when the engine must also provide power for maximum acceleration. While power management has provided the opportunities for flywheel batteries in vehicles, advances in technology have made the systems more practical. The key advance is the development of very high strength, long-life composites. These materials have significantly improved the energy density in the system over what could be achieved with a steel wheel by permitting much higher rotational velocities. So, smaller, lighter wheels can store energy in the range from less than a kilowatt-hour to more than 100 kilowatt-hours. Other important advances have been in magnetic bearings that allow reliable high-speed operation and in power electronics to control the output power. Vehicular operation does produce new issues that were less significant in the more traditional stationary applications. One of the most obvious among these is torque management. In charging or discharging a flywheel, the rotational velocity is changed and a torque is produced. For example, systems intended for the International Space Station, where torque management is critical, the initial plan is to cancel torque by using two counter-rotating flywheels. Once confidence is gained in this mode of operation, energy will be distributed among various flywheels to produce the net torque needed for stable operation. For terrestrial vehicles, the flywheel is in a gimbled compliant mount with the axis of rotation orthogonal to the plane of vehicle motion. This orientation permits torque to be compensated by the magnetic bearings and the mount. Tests show that the mount and bearing system can accommodate the shock and vibrations, as well as traveling up or down grades, expected under on-road operation.
Frequency response characteristics of fluid-immersed hairbeds
(2022) Freeman, Naiesa
Monitoring of Defects in Induction Motors Through Air-Gap Torque Observation
(IEEE, 1995-09) Hsu, J.S.;
This paper suggests a method to monitor defects such as cracked rotor bars and the shorted stator coils in induction motors. Air-gap torque can be calculated while the motor is running. No special down time for measurement is required. Data of the air-gap torque for a motor should be periodically kept for comparison purposes. Since more data than just a line current are taken, this method offers other potential possibilities that cannot be handled by examining only a line current. The theoretical foundation for this proposed method is presented. Experiments conducted on a 5-hp motor show the validity and potential of this approach. Further studies are planned to extend the proposed method in detail and to monitor defects developed in other types of rotating machines
Possible Errors in Measurement of Air-Gap Torque Pulsations of Induction Motors
(IEEE, 1992-03) Hsu, J.S.; Woodson, H.H.; Weldon, W.F.
Measurements based on the accurately obtained air gap flux data using either the search-coil or the Hall-effect approach are not error proof. This is because even the unbalanced leakage effects can be reduced to a minimal value by measuring the air-gap flux at the tip of the slots. The magnetic paths of different axes may not be balanced at any instant. This generates a computed measured torque value that includes an uncancellable error. Pulsating torque measurements using only the motor terminal data without the requirement of additional search coils or Hall-effect sensors are a convenient approach to obtain the air gap torque value. This method is further studied for the purpose of understanding the source of its possible errors
Time Domain Steady-State Torque Calculation of Voltage Source Pulse-Width-Modulated Inverter Fed Induction Motors, Part I: Theoretical Analysis
(IEEE, 1991) Hsu, J.S.;
Evaluation of torque pulsation associated with the harmonics of pulse width modulated (PWM) inverter-fed drives is important for a quiet and smooth operation. This paper discusses an analytical method for the steady state torque calculation of the voltage source PWM inverter fed induction motors. Equations derived from the 1-2-0 coordinate system are used. A sample calculation is included for the illustration of practical application.
Time-Domain, Steady-State Torque Calculation of Voltage-Source Pulse-Width-Modulated Inverter Fed Induction Motors
(0000-00-00) Hsu, J.S.;
Evaluation of torque pulsation associated with the harmonics of pulse width modulated (PWM) inverter-fed drives is important, particularly at low speed. This paper discusses an analytical method for the steady-state torque calculation of the voltage-source PWM inverter fed induction motors. Equations derived from the 1-2-0 coordinate system are used. A sample calculation is included for the illustration of practical application.
Torque And Optical Traps
(2008-12) Ibeneche, C.; Ibeneche, Chieze
Optical traps are an important tool for research in the field of single molecule biophysics. Recent advances in optical trapping have extended their functionality from simple linear manipulation and measurement of forces, to now the ability to rotate objects and measure torques. This mini review summarizes these recent developments of the optical trap as a tool to apply and measure torque in biophysical applications.