Tommy V. Frandsen

Experimental evaluation of a motor integrated permanent magnet gear

This paper presents test results of a new motor integrated permanent magnet gear and clarifies a path for future optimizations. The prototype, which fabrication also is described, is initially targeting electrical traction for vehicles. Basic measured parameters in form of back-emf, stall torque and inductances are all in line with finite element calculations. However very high rotational losses are present in the prototype and these losses are higher than the calculations. Some of the losses are present due to poor aspects in the fabrication of the prototype, while others are identified to be caused by a non optimal diameter/length aspect ratio. The torque density is superior, the copper losses is only a fraction of the copper losses in other traction motors. With the proposed aspects to reduce the rotational losses is it believed that the unit has a great potential.

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.

Experimental Evaluation of a Motor-Integrated Permanent-Magnet Gear

This paper presents test results of a new motor integrated permanent magnet gear and clarifies a path for future optimizations. The prototype, which fabrication also is described, is initially targeting electrical traction for vehicles. Basic measured parameters in form of back-emf, stall torque and inductances are all in line with finite element calculations. However very high rotational losses are present in the prototype and these losses are higher than the calculations. Some of the losses are present due to poor aspects in the fabrication of the prototype, while others are identified to be caused by a non optimal diameter/length aspect ratio. The torque density is superior, the copper losses is only a fraction of the copper losses in other traction motors. With the proposed aspects to reduce the rotational losses is it believed that the unit has a great potential.

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.

Improved motor intergrated permanent magnet gear for traction applications

This paper presents a new demonstrator of a motor integrated permanent magnet gear for traction applications. The main purpose of the new demonstrator is to reduce rotational losses, which in the first version were too high. To mitigate the high rotational losses several aspects are improved in the design such as lower diameter/length ratio, imbedded and segmented magnet design, dummy slots etc. Also, improvements in the mechanical and thermal layout are addressed by using the central segmented cylinder as output and adding liquid cooling. The calculated rotational loss is reduced with more than a factor “8” resulting in a simulated efficiency above 95% in a broad torque-speed range. The 2D FEA calculated torque density of the new demonstrator is 107 kNm/m3 compared to 113 kNm/m3 from the first version. I.e. the loss reduction has not been a compromise with torque density. Various manufactured parts are presented together with some initial measurements.

Loss investigation of Motor Integrated Permanent Magnet Gear

This paper presents an investigation of the eddy-current losses caused by 3D effects in a Motor Integrated Permanent Magnet Gear (MIPMG). Two prototypes of a MIPMG have been designed and build to be used as traction units for an electric vehicle. The measured efficiency of the MIPMG is superior in urban traffic when compared to state of the art direct drives, even though the measured rotational losses are up to more than 230% higher than estimated with calculations based on 2D FEA. A hypothesis was that large eddy-currents occur in the end-shields of the machine which are made of stainless steel. In order to validate or reject this hypothesis a practical approach is taken by manufacturing new end-shields in a non-conducting material. Measurements of the rotational losses with the new end-shields proved the hypothesis wrong. The results with the new end-shields are verified by 3D FEA and a new hypothesize is made regarding the source of the additional rotational losses.

Slip torque investigation and magnetic redesign of motor integrated permanent magnet gear

This paper presents an investigation of 20% difference between the measured and calculated slip torque of a Motor Integrated Permanent Magnet Gear (MIPMG) prototype. The High Speed (HS) side of the Magnetic Gear (MG) was fixed by loading the motor when conducting the slip torque measurement. Suspicion of the motor saturating before the MG reached peek torque and thus measuring the maximum torque of the motor instead, made the method questionable. The MIPMG has been modified to lock the HS side of the MG mechanically and new measurements have been conducted but with the same low slip torque as result. It was realized that some magnets most likely are partly demagnetized due to an inappropriate magnetic design which can explain the measured slip torque to be lower than the results from static 2 and 3D FEA. With the discovered demagnetization and several years of experience with the technology, the MIPMG is theoretical redesigned and semi optimized regarding the use of magnet material while maintaining a reasonable torque density and high efficiency.

Practical investigation of end effect losses in a Motor Integrated Permanent Magnet Gear

This paper presents a practical investigation of the eddy current losses caused by 3D effects in a Motor Integrated Permanent Magnet Gear (MIPMG). Two prototypes of a MIPMG have been designed and build to be used as traction units for an electric vehicle. The measured efficiency of the prototype MIPMGs is superior in urban traffic when compared to state of the art direct drives, even though the measured rotational losses are more than two times higher than estimated with calculations based on 2D Finite Element Analysis (FEA). Based on 3D Magnetostatic FEA, the prototype has been modified to reduce 3D eddy currents in the machine. Material is removed and new parts are made in a non-conducting material. After the modifications of the prototype, the rotational losses have been measured and compared to the earlier measurements and the 2D based calculated losses. The rotational losses have been reduced, thus, making the gap between the measured and calculated losses smaller and increased the efficiency. Assumption regarding unaccounted losses is elaborated, and the presented work makes it possible to make the design of the next generation of MIPMG even better, with lower losses and higher efficiency.

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.

Start-up problem with an induction machine and a permanent magnet gear

This paper presents the preliminary work conducted to design a magnetic gear (MG) integrated with a fan and driven by an grid connected induction machine (IM). A start-up problem with a MG, which occurs due to a high oscillating torque and a high breakdown torque of the IM when starting up directly from grid, has been investigated. Based on a preliminary design proposal of a MG-fan system a simulation model is developed and the effect of changing different parameters has been studied. A test set-up has been build and different tests are carried out to verify the simulation model. The relation between the mass moment of inertia of the low and high speed side of the MG and their effects on the start-up problem have been examined. It is concluded by simulation that an increased mass moment of inertia on the high speed side of the MG can overcome the start-up problem, and this is verified by adding extra mass moment of inertia on the test-setup. Good agreement between the calculated natural frequency of the test system and measurements has been experienced, both with and without extra mass moment of inertia added to the system.