Engines & Power Electronics : Motors

Engines & Power Electronics Portfolios


New Rotor Magnet Configuration Delivers Greater Efficiency at a Lower Price

UW–Madison researchers have developed a streamlined sinusoidal rotor magnet design for interior permanent magnet machines.

By altering the classic rectangular block design for embedded magnet stacks in favor of a sinusoidal, axially varied orientation, researchers have increased the efficiency of rotors in IPMMs in a twofold fashion: Not only does this new design reduce the amount of magnet material necessary for rotor production, but it also provides an optimized distribution of flux that significantly reduces torque pulsation and spatial harmonics. The new design is easy to manufacture and is complementary to rotors already in existence.

Axial Flux-Switching Permanent Magnet Machine for High Speed Operation

UW–Madison researchers have developed a new axial FSPM machine that can be run at high speed with less fundamental frequency required, therefore overcoming one of the largest barriers to adoption. The new design features innovative axial flux topologies with offset rotor and/or stator structures.

Induction-Type Electrostatic Machine Improves Torque Profile, Design Flexibility

UW–Madison researchers have developed a versatile new design for large-scale electrostatic machines. The new design simplifies manufacturing by eliminating plates in favor of interdigitated pegs immersed in dielectric fluid. Concentric conducting ‘sleeves’ fit around/in between the rows of pegs and are used to shape the electrostatic field, reduce drag and improve torque characteristics and mechanical strength. Unlike conventional designs, torque is produced from electrostatic induction.

New Electrostatic Motor Design Simplifies Manufacturing

UW–Madison researchers have developed a versatile design for large-scale electrostatic machines. The new design features circular rows of pegs attached to plates and immersed in dielectric fluid. The pegs come in and out of alignments as the plates rotate. The shape, length and positioning of the pegs can be varied as needed to achieve higher torque.

Motor for Electric Vehicles Solves Load/Loss Tradeoff

UW–Madison researchers have developed a new IPM design methodology that offers a solution to conventional performance tradeoffs.

The new design features variable flux linkage characteristics to reduce iron and copper loss under low and high load conditions, respectively. The design does not compromise torque capability and exploits flux leakage already present in every PM machine. In other words, compared to previous IPMs, this technology is able to convert a weakness into an advantage.

More specifically, the rotor geometry is designed such that flux leakage can be shifted to cross the air gap and become desirable flux linkage when stator current is applied. It can be increased or decreased as needed based on load conditions.

Lower Cost Motor for Electric Vehicles

Building on their work, the researchers have developed an improved FI-IPM machine and control method. The new design employs thin, low-coercivity magnets and allows re-magnetization using the stator winding and system power control. Magnetic force is reduced, and voltage is limited in high-rotation zones in which normal motors require flux weakening control. Re-magnetization is performed in zones that require low rotation and high torque, and the desired magnetic flux is obtained in the magnets.

Flux-Switching Permanent Magnet Machine for High Speed Operation

UW–Madison researchers have developed a new FSPM machine that can be run at high speed with less fundamental frequency required, therefore overcoming one of the largest barriers to adoption. The new design relies on innovative radial flux topology that features an offset rotor structure, dual stators and concentrated coil windings.

Lighter, Cheaper Multilevel Converter for Adjustable Speed Drives

UW–Madison researchers have developed a new multilevel converter design that does not require any extra capacitors, diodes or isolated voltage sources. This reduces costs, size and insulation requirements compared to conventional multilevel converters.

The new design is based on two multiphase inverters electrically coupled in series. The key feature is that they share the same input source (e.g., a single rectifier, DC grid or batteries). Other designs require separate isolated voltage sources. In this design, the output AC terminals of the inverters power different groups of machine windings, and the total output voltage is combined inside the machine without additional components.

Induction Motor Wastes Less Power

UW–Madison researchers have developed a method to control the supply of reactive power to/from an induction motor so that it operates at approximately unity (1:1) power factor. In other words, the motor consumes voltage and current in phase from the terminals of the electric grid.

In essence, multiphase voltage from the grid is applied to one side of the motor’s open stator windings. A processor receives this voltage and determines its phase. At the same time, stator currents are measured from the second side of open windings and converted to a type of reference frame having voltage on one axis. Based on this reference frame, a second output voltage signal is determined and applied to the second side of open windings.

Vernier Motor Uses Less Rare Earth Materials

UW–Madison researchers have developed a new vernier machine that outperforms other PMVM designs.

The new motor features a central rotor with spokes of magnets. The magnets can be ferrite-based or made of a minimal amount of rare earth material. The rotor is sandwiched by a pair of notched stators, each separated from the rotor by an air gap and wound by stator windings that form magnetic poles. In contrast to traditional PM machines, the number of rotor magnetic pole pairs is much greater than the number of stator winding pole pairs. Still, the motor is able to achieve smooth torque given its design.

In effect, the new design produces a rotating magnetic field that travels much faster around the air gap than the rotor. Increased rate of change of flux linkage means more voltage is induced.

New Capacitive Method for More Efficient Power Generation

A UW–Madison researcher has developed a varying capacitance rotating electrical machine for an improved power generation system. The design comprises a rotor, stators, a spring element and conductive plates. The device utilizes capacitive coupling that is obtained between rotating and stationary capacitor plates by allowing one plate to float on a cushion of fluid (either air or liquid). These “air bearings” allow for much smaller gaps between the plates than existing methods. When combined with high rotational speeds, they enable an increase in power density.

New Flexible Mechanical Structure for Improved Wireless Power Transmission

UW–Madison researchers have developed a wireless power transfer technique that uses opposing pairs of capacitor plates, eliminating many of the reliability and maintenance issues present in current designs. The design provides a mechanism to power the electromagnets in wound field synchronous machines by which power is transferred to the rotor via capacitive coupling. The device consists of a flexible plate structure and glides on a cushion of air while the system is in motion. The system comprises a rotor including at least one electrical coil, a conductor, an electrical rectifier and first, second, third and fourth capacitor plates. The device may further comprise a power generation circuit providing alternating current power to at least one electrical coil and a capacitance monitor to provide an output signal indicating velocity and/or position of the rotor.

Brushless Synchronous Motor Utilizing Third Harmonic Excitation for Power Transfer to Rotor

UW-Madison researchers have developed a brushless synchronous motor that enables power to be transferred to the rotor without requiring slip rings, brushes or other failure-prone components. Unlike traditional synchronous machines where all windings are connected, in this improved design there are three stator windings, which together generate square waves, and two windings mounted to the rotor. The generated square waves induce a voltage in the first rotor winding to form a plurality of third harmonic coils, which are then applied to the second rotor winding to create a brushless, synchronous motor.

Permanent Magnet Synchronous Motor Self-Sensing Drive System

UW-Madison researchers have developed a permanent magnet synchronous motor system that enables position sensorless rotor position estimation, which has been demonstrated to be effective even when a smooth cylindrical permanent magnet is positioned on the surface of the rotor. The system includes a rotor with a permanent magnet surface providing multiple angularly spaced magnetic poles and a stator fitting around the rotor so that the rotor can rotate within the stator. Within the stator, angularly spaced teeth extend inward toward the rotor, and electrically conductive coils are wound around at least some of the teeth to apply a magnetic field to the teeth. The system also may employ concentrated windings that will accentuate the stator-based saliency detected by the system. 

The power electronic drive attached to the motor not only provides the basic power conversion input, but also injects an electrical excitation signal into the coils at a frequency higher than the primary power conversion drive frequency. The primary power conversion input frequency is controlled to produce torque and thereby control rotation of the rotor. The superimposed high frequency injected signal is used to track rotor position by detecting variations in the injected signal that are functionally related to the rotor position and to the magnetic saturation of the stator teeth caused by the rotor magnetic fields.

This injection-based, saliency tracking method permits position sensorless operation for SPMSMs having little to no saliency on the rotor, eliminating the need for the inclusion of a separate position sensor in such systems. The system also is adaptable to a wide range of stator designs.

Improved Engine Carburetion with Porous Walled Fuel Tube

UW–Madison researchers have developed an improved system for engine carburetion utilizing an emulsion tube. A porous wall surrounds an inner passage, where air travels around one side of the wall and fuel travels around the opposite side. Air is supplied through the pores of the tube to aerate the fuel, and the aerated fuel is expelled into a venturi while engine intake air further mixes with the fuel. The emulsion tube provides a high degree of fuel/air mixing across the entire range of intake airstream flow rates. The tube may have one or more holes drilled through its outer surface to the inner passage to assist in custom tailoring the fuel/air mix for the engine to provide the desired fuel/air ratio across the engine’s operation range of intake air flow rates.

The pore sizes and densities may vary at different locations along the length of the tubular body to further customize fuel/air ratio and flow rates. However, variable-porosity tubes can be difficult and expensive to construct. The improved carburetion design provides an alternative arrangement with an emulsion tube formed of a tubular body with three axially aligned sections that each have different average pore sizes and densities to vary porosity discretely over the length of the tubular body.

The porous emulsion tube generates a foamy “bubbly flow” across the entire operating range of air intake flow rates of common carburetors, with a well-mixed emulsion at the tube’s exit far superior to that produced with conventional emulsion tubes. With appropriate tailoring of the porosity of the emulsion tube, a linear relationship between fuel flow and air intake flow may be provided, resulting in improved efficiency and reduced emissions.

Field Controlled Axial Flux Permanent Magnet Electrical Machine

UW-Madison researchers have developed an electrical machine that combines a variable DC coil excitation with permanent magnet excitation to control the flux in a cost-effective manner. This design modifies the multiple-rotor, multiple-stator, axial-flux permanent magnet machine by adding one or two DC field windings to control the air gap flux and to provide a path for the DC flux through a modification of the rotor structure. The resulting field-controlled, axial-flux, surface-mounted permanent magnet machine offers a less expensive and more readily implemented flux control.

Dual-Rotor, Radial-Flux, Toroidally-Wound, Permanent Magnet Machine with High Efficiency and High Torque Density

UW-Madison researchers have developed a machine topology suitable for high speed applications that simultaneously exhibits high efficiency and high torque density. Their dual-rotor, radial-flux, toroidally-wound, permanent magnet machine also employs inexpensive ferrite magnets, making these machines inexpensive to produce.

Adjustable Speed Drive For Single-Phase Induction Motors

UW-Madison researchers have developed a simple and inexpensive adjustable speed drive for use with low-cost, single-phase induction motors. The drive can operate in full-speed mode with high starting torque, and in at least one lower-speed mode suitable for applications such as fan motor drives.

Improved Dual Stator Induction Machine

UW–Madison researchers have developed a dual stator winding induction machine that can be built with minimal modifications to standard winding configurations. The device comprises a stator having two separate stator windings with input terminals that are separately supplied with drive power. The windings have a different number of poles that are in a ratio of 1:3 (a 2-6 pole combination is most advantageous), which eliminates magnetic coupling and decouples the torques produced by each set of windings. The machine can be driven at zero and low speed operation without the need for a rotor position encoder to provide rotor position and speed feedback.