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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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1,347 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Excitation control of dual-wound machines for coupling mitigation

A dual-wound machine comprises a dual-wound generator supplying power to two separate powered zones. The generator comprises a wound rotor with a field winding and a stator with two sets of phase windings and a field control loop that controls the excitation voltage applied to the field winding and therefore the magnetic field produced by the rotor, in order to maintain a constant field flux in the generator and mitigate dynamic coupling between the two sets of phase windings when supplying power to unbalanced loads.

Rashkin, Lee Joshua↗
DOE OSTI2024

A Review of Ring Motors with Integrated Loads

Ring motors are electric machines that are typically characterized by having a hollow rotor / stator, a small difference between the inner and outer radii, and a large outer diameter relative to the axial length. The hollow portion of the ring motor allows integrating loads, such as an aerial or marine propeller, enabling power-dense systems. This paper reviews integrated ring motor designs from literature across different applications. Based on this review, first, design trends and performance parameters are identified and compared with conventional radial flux machines. Next, the bearing challenges posed by the unique form-factors of these machines are identified and approaches to realize bearings are presented. Finally, a research outlook is presented that identifies the benefits of applying multi-physics optimization, additive manufacturing, and bearingless machine technology to realize improved integrated ring motor designs.

Asgodom, Adonay↗
DOE OSTI2026

Brushless Excitation for Wound-field Synchronous Machines using Multi-harmonic Windings

Wound-field synchronous machines (WFSM) are promising alternatives to electric machines with permanent magnets (PM). The ability to control the rotor field in these machines makes them well-suited to safety critical applications, while the absence of rare-earth permanent magnets makes these machines sustainable. The WFSM rotor excitation schemes have traditionally used carbon brushes, which significantly reduces the reliability of these machines, limiting their widespread adoption. To overcome this limitation and improve the reliability of WFSMs, several brushless rotor excitation schemes have been developed. However, most of these systems require additional windings or dedicated power electronics, making them expensive and limiting achievable power-density. In this paper a new brushless excitation scheme is proposed. In this scheme, a multiphase, multi-harmonic stator winding is designed. This winding can independently control two spatial harmonics in the airgap of the machine; the first to create torque and the second to wirelessly transfer power to the rotor to excite it.

Gadiyar, Nishanth [ORNL] (ORCID:0000000348267524)↗
DOE OSTI2022

A Two-Step Control Approach for Torque Ripple and Vibration Reduction in Switched Reluctance Motor Drives

The objective of this work is to reduce the torque ripple and vibration in Switched Reluctance Motor (SRM) drives. To achieve such a goal, a two-step approach is proposed. In the first step, the reference current is profiled using an optimization method, aimed to reduce the torque pulsation. In the second, the optimum current profile is applied to the SRM through an adaptive hysteresis band controller to actively cancel the radial vibration. The proposed technique uses an optimization procedure based on the Field Reconstruction Method (FRM) and Non-Derivative Optimization Method to find the optimal current profile that mitigates the torque pulsation, however, the investigation has shown that the proposed excitation leads to a higher radial vibration, which has been mitigated by using an adaptive hysteresis band controller. The theoretical basis for the proposed approach is initially presented, followed by system modeling and simulation. In addition, experimental verification has been conducted using an 8/6 SRM to show the feasibility of the proposed approach. The proposed method alleviates the acoustic noise and torque pulsation in SRM and offers an effective step towards the prevalent use of SRM in a wide range of applications.

42 ENGINEERING↗
DOE OSTI2022

Spaced Orthocyclic Winding Pattern for Improved Die Compressed Coils

Winding fill, coil fill, or packing factor, is critical to the performance of many types of electromagnetic devices from electric machines to actuators, transformers, inductors, etc. One technique to increase the packing of conductors in the winding area is to compress round magnet wire conductors in a die, so that they deform and air voids between coil turns are removed. The winding layout of the coil turns on a bobbin before compression has a direct impact on the achievable coil fill and the damage to the coil insulation or conductors after compression. It is thought that winding the turns in an orthocyclic pattern on the bobbin before compression would minimize damage to the turns. This however causes turns to displace during the winding compression process. A new pre-compression winding pattern is proposed, a spaced orthocyclic winding, to minimize turn displacement and damage. A design of experiments study has been carried out to optimize this winding method and to compare it to the traditional orthocyclic winding.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

Low Space Harmonic Content Windings (LSHWs) Applied to Improve the Pareto Front in Design Optimization of Electric Machines

In design optimization of high performance electric machines where the power density is increasingly a key metric, it is often desirable to maximize the average torque output within a given volume. However, if a smooth output is also required, the torque ripple may become a hurdle as it tends to increase with the average torque for conventional windings. A direct benefit of low space harmonic content windings (LSHWs), featuring the suppression or elimination of targeted non-working orders in the winding magnetomotive force (MMF), is the torque ripple reduction. This paper provides a detailed analysis of torque ripple pairs and the space-time harmonic order mapping, with concise results that applies to both distributed windings and fractionalslot concentrated windings (FSCWs) of any slot/pole combination. Metamodel-based optimizations are performed to compare two LSHWs with a conventional winding. Improved Pareto fronts are validated, which confirms higher torque producing capabilities at various torque ripple thresholds for LSHWs.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1997

Rotary Piezoelectric Motors Actuated by Traveling Waves (abstract)

Piezoelectric rotary motors are being developed as a drive mechanism for miniature spacecraft instruments and subsystems. The technology that has recently emerged in commercial products requires more rigorous analytical tools for effective design. The theoretical predictions and the experimental corraboration showed a remarkable agreement and they will be presented and discussed in this paper.

Actuators piezoelectric motors active materials ul↗
NASA NTRS1998

Rotary Ultrasonic Motors Actuated by Traveling Flexural Waves

Efficient miniature actuators that are compact and consume low power are needed to drive telerobotic devices and space mechanisms in future NASA missions. Ultrasonic rotary motors have the potential to meet this NASA need and they are developed as actuators for miniature telerobotic applications.

Piezoelectric↗
NASA NTRS1999

Rotary Motors Actuated by Traveling Ultrasonic Flexural Waves

Efficient miniature actuators that the compact and consume low power are needed to drive space and planetary mechanisms in future NASA missions. Ultrasonic rotary motors have the potential to meet this NASA need and they are developed as actuators for miniature telerobotic applications.

piezoelectric↗