Carlos R. Morrison

Electromagnetic Forces in a Hybrid Magnetic-Bearing Switched-Reluctance Motor

We have performed analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM). An MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this paper has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped lamination segments. The hybrid rotor is levitated with only one set of four stator poles, while a second set of four stator poles imparts torque to the scalloped portion of the rotor, which is driven in a traditional switched reluctance manner by a processor. We performed static torque and radial force analysis of rotor poles oriented to achieve maximum and minimum radial force loads on the rotor. The objective was to assess whether simple one-dimensional magnetic circuit analysis is sufficient for preliminary evaluation of this machine, which may exhibit strong three-dimensional electromagnetic field behavior. We employed two magnetic circuit geometries, approximating the complex topology of the magnetic fields in and around the hybrid rotor, in formulating the electromagnetic radial force equations. The experimental and the theoretical radial force load predictions agreed reasonably well with typical magnetic bearing derating factors applied to the predictions.

Fully Suspended, Five-Axis, Three-Magnetic- Bearing Dynamic Spin Rig With Forced Excitation

A significant advancement in the dynamic spin rig (DSR), i.e., the five-axis, three-magnetic-bearing DSR, is used to perform vibration tests of turbomachinery blades and components under rotating and non-rotating conditions in a vacuum. The rig has three magnetic bearings as its critical components: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feedforward control feature, which enables the excitation of various modes of vibration in the bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and non-rotating, unbladed rotor and a fully levitated, rotating and non-rotating, bladed rotor in which a pair of blades were arranged 180° apart from each other. These tests include the “bounce” mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For non-rotating blades, a blade-tip excitation amplitude of approximately 100 g A−1 was achieved at the first-bending critical (≈144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 1.778×10−3m (70 mils) was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 90° relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

Propulsion Electric Grid Simulator (PEGS) for Future Turboelectric Distributed Propulsion Aircraft

NASA Glenn Research Center, in collaboration with the aerospace industry and academia, has begun the development of technology for a future hybrid-wing body electric airplane with a turboelectric distributed propulsion (TeDP) system. It is essential to design a subscale system to emulate the TeDP power grid, which would enable rapid analysis and demonstration of the proof-of-concept of the TeDP electrical system. This paper describes how small electrical machines with their controllers can emulate all the components in a TeDP power train. The whole system model in Matlab/Simulink was first developed and tested in simulation, and the simulation results showed that system dynamic characteristics could be implemented by using the closed-loop control of the electric motor drive systems. Then we designed a subscale experimental system to emulate the entire power system from the turbine engine to the propulsive fans. Firstly, we built a system to emulate a gas turbine engine driving a generator, consisting of two permanent magnet (PM) motors with brushless motor drives, coupled by a shaft. We programmed the first motor and its drive to mimic the speed-torque characteristic of the gas turbine engine, while the second motor and drive act as a generator and produce a torque load on the first motor. Secondly, we built another system of two PM motors and drives to emulate a motor driving a propulsive fan. We programmed the first motor and drive to emulate a wound-rotor synchronous motor. The propulsive fan was emulated by implementing fan maps and flight conditions into the fourth motor and drive, which produce a torque load on the driving motor. The stator of each PM motor is designed to travel axially to change the coupling between rotor and stator. This feature allows the PM motor to more closely emulate a wound-rotor synchronous machine. These techniques can convert the plain motor system into a unique TeDP power grid emulator that enables real-time simulation performance using hardware-in-the-loop (HIL).

A Resonant Damping Study Using Piezoelectric Materials

o C, but they are researching materials that can function up to 1000 o C, which should work well within an engine. These and other smart materials can provide significant structural damping performance depending upon their design and application, and further development of smart damping systems using them. These materials will be investigated for both passive damping and active damping devices for the turbomachinery blade application. Candidate smart materials must demonstrate sufficient levels of structural damping over the life of the structure in the expected operating environments. The models developed in this study must be validated through simulation and experimental testing for proof of operation and viability. The piezoelectric damper solution consists of piezoelectric patches for sensing and actuation which are controlled by an active or passive control circuit. Extensive work has already been performed in this area [2-3]. However, in future we plan to extend these results into higher temperature regimes and under the centrifugal loading experienced in the engine environment. We will investigate using high temperature piezoelectric patches as blade dampers. The piezoelectric damper will be tuned to remove energy at the resonance frequencies, thereby reducing vibration amplitude. It will not be sized to actuate the blade or significantly change the stiffness of the blade. Piezoelectric materials produce a voltage when deformed and enable them to be used as sensors. This property also enables them to be used as passive vibration dampers since they convert mechanical energy into electrical energy, which can be dissipated in a shunting circuit. Placing shunted piezoelectric patches in appropriate locations on a blade can reduce resonant stresses for a target mode. Piezoelectric materials can also be used for active vibration control as actuators and sensors that can be used to yield damping over a wider frequency range. A schematic sketch of the system is depicted as shown in Figure 1.

Control Study for Five-Axis Dynamic Spin Rig Using Magnetic Bearings

The NASA Glenn Research Center (GRC) has developed a magnetic bearing system for the Dynamic Spin Rig (DSR) with a fully suspended shaft that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteroplolar radial magnetic bearings and a thrust magnetic bearing and the associated control system were integrated into the DSR to provide magnetic excitation as well as non-contact magnetic suspension of a 15.88 kg (35 lb) vertical rotor with blades to induce turbomachinery blade vibration. For rotor levitation, a proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, more blade vibration amplitude, and energy savings for the system. The test results of a variety of controllers that were demonstrated up to 10,000 rpm are shown. Furthermore, rotor excitation operation andconceptual study of active blade vibration control are addressed.Copyright

Control of Fan Blade Vibrations Using Piezoelectrics and Bi-Directional Telemetry

A novel wireless device which transfers supply power through induction to rotating operational amplifiers and transmits low voltage AC signals to and from a rotating body by way of radio telemetry has been successfully demonstrated in the NASA Glenn Research Center (GRC) Dynamic Spin Test Facility. In the demonstration described herein, a rotating operational amplifier provides controllable AC power to a piezoelectric patch epoxied to the surface of a rotating Ti plate. The amplitude and phase of the sinusoidal voltage command signal, transmitted wirelessly to the amplifier, was tuned to completely suppress the 3rd bending resonant vibration of the plate. The plate’s 3rd bending resonance was excited using rotating magnetic bearing excitation while it spun at slow speed in a vacuum chamber. A second patch on the opposite side of the plate was used as a sensor. This paper discusses the characteristics of this novel device, the details of a spin test, results from a preliminary demonstration, and future plans.© 2011 ASME