Rasmus Koldborg Holm

Design of a Magnetic Lead Screw for Wave Energy Conversion

This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state of the art regarding linear permanent-magnet generators and MLSs is given, leading to an introduction of the MLS and a presentation of the results from a finite-element analysis used to find the magnetic forces. Furthermore, the force per magnet surface area measure is presented as a better alternative to the force density measure, which is often used for linear magnetic devices. Based on this, the overall design of a 500-kN MLS is presented focusing on the bearing supports used to compensate for the magnetic attraction forces and the resulting deflection of the rotor. In addition, in order to avoid some of the assembling-related disadvantages of using surface-mounted magnets, an embedded-magnet topology is proposed. To demonstrate the technology, a scaled 17-kN MLS is presented together with experimental results.

Motor Integrated Permanent Magnet Gear in a Battery Electrical Vehicle

This paper presents the physical construction and test results of two new demonstrators of a Motor Integrated Permanent Magnet Gear (MIPMG), which is a second version of an already tested demonstrator. The demonstrators will be used as traction units for a Battery Electrical Vehicle (BEV) and the background for the specifications are elaborated. Simulated as well as measured results of rotational losses of the first and second version are compared. The efficiency of the new design is investigated and compared to the drivetrain of the Tesla Roadster and two direct drive axial flux motors in a few operating points, the MIPMG v.2 seems superior when used as traction unit in urban traffic.

Design and test of a novel magnetic lead screw for active suspension system in a vehicle

This paper deals with the development of a magnetic lead screw (MLS) for the active suspension system in a vehicle. Initially, a brief introduction to the active suspension system of a vehicle, is given, thereby identifying the benefits of having an active suspension system in a normal vehicle. Furthermore the Magnetic Lead Screw is introduced and its benefits when used with an active suspension system are discussed. Based on a model of a quarter car, the design specifications for the MLS active suspension system are found, which leads to a design study. The design study investigates the relation between lead and equivalent mass. Additionally using a Bode diagram, the frequency response of the hydraulic standard damper and various configurations of the MLS active damper are compared. The designed prototype is constructed and various tests are performed, leading to full efficiency map for the developed prototype and identification of the total losses of the MLS system. It is concluded that the designed prototype functions as expected, however a decrease in stall force from the calculated 3D FEM value of 3.7 kN to approx. 3 kN is measured. Finally the efficiency map indicate the possibility of harvesting energy from the vehicle suspension system independently of damping velocity.

Motor integrated permanent magnet gear in a battery electrical vehicle

This paper presents the physical construction and test results of two new demonstrators of a motor integrated permanent magnet gear (MIPMG), which is a second version of an already tested demonstrator. The demonstrators will be used as traction units for a battery electrical vehicle and the background for the specifications are elaborated. Simulated and measured results of rotational losses of the first and second versions are compared. The efficiency of the new design is investigated and compared with three direct-drive motors in a few operating points, and the MIPMG v.2 seems superior when used as a traction unit in urban traffic.

Theoretical and Experimental Loss and Efficiency Studies of a Magnetic Lead Screw

This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low speed high force linear motion of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17 kN demonstrator and a simplified motor model showed an efficiency of only 80 % at low load, however it was expected that the efficiency should be above 95 %. For understanding and future optimization a detailed study of the loss in the MLS is presented with the aim of identifying and segregate various loss components which was not accounted for in previously results. This is done through theoretical loss calculations and various experiments. It is concluded that the linear guide is the dominating loss component in the MLS demonstrator, while the losses in the axial thrust bearing is not as dominant as expected, further an efficiency above 94 % was measured.

Theoretical and experimental loss and efficiency studies of a magnetic lead screw

This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low speed high force linear motion of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17 kN demonstrator and a simplified motor model showed an efficiency of only 80 % at low load, however it was expected that the efficiency should be above 95 %. For understanding and future optimization a detailed study of the loss in the MLS is presented with the aim of identifying and segregate various loss components which was not accounted for in previously results. This is done through theoretical loss calculations and various experiments. It is concluded that the linear guide is the dominating loss component in the MLS demonstrator, while the losses in the axial thrust bearing is not as dominant as expected, further an efficiency above 94 % was measured.

Design and development of a MLS based compact active suspension system, featuring air spring and energy harvesting capabilities

This paper describes the design and development of an novel Magnetic Lead Screw based active suspension system for passenger vehicles, using a new MLS topology. The design is based on performance specifications found from ISO road profiles, with a maximum harvested energy approach. By integrating the PMSM motor with the MLS, it possible to construct a very compact design with an integrated air spring. The prototype is build and frictional losses and efficiency for the MLS damper unit are measured. Additional the stall force and stall torque are measured for the build prototype to validate the developed 3D FEM model. It was concluded that the MLS damper unit was capable of delivering a mean efficiency of 80% for a full up and down stroke (+/− 48 mm).

A novel magnetic lead screw active suspension system for vehicles

This paper encompasses a detailed study of the redesign of a novel Magnetic Lead Screw (MLS) active suspension system for possible regeneration of the energy dispatched in the suspension system and active control of vehicle body movement. The MLS converts a low speed high force linear motion of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. The paper describes the drawback of the first MLS prototype v1.0 developed for active suspension system, which lead to a new design of the MLS prototype named v1.5. Furthermore the paper introduces detailed efficiency and thermal tests of the redesigned MLS prototype v1.5, and an investigation of the durability of the linear guides in the MLS v1.5.

Design and test of a reluctance based magnetic lead screw PTO system for a wave energy converter

This paper deals with the design and test of a Reluctance based Magnetic Lead Screw Power Take Off (PTO) system for a Wave Energy Converter for powering a LED light buoy. In order to meet the power requirement for the LED marking light, measurements of the seastate at the specific location of the buoy is carried out using a special wave measurement buoy. The data is used to set up a simulation model of the possible harvested energy using a Magnetic Lead Screw (MLS) as the core component of the PTO system. Specifications of the MLS generator, in terms of stall force, lead, stroke etc. are found based on these simulations. Design of the MLS unit is carried out using FEM models of the MLS magnetic circuit, together with mechanical design consideration for minimizing the total cost of the device. Test of efficiency and stall force of the built prototype is carried out and presented.

Magnetically geared machines for electrical vehicle and renewable energy applications

Early in this millennium a paper by K. Attalah and D. Howe [1] re-ignited a worldwide research on magnetic gear devices.