Compact permanent-magnet generator for hybrid vehicle applications

In hybrid electric vehicle (HEV) drivetrains an electrical generator is coupled onto the shaft of an internal-combustion engine (ICE) in order to process either the entire or a given fraction of the traction power required by the vehicle wheels. As such an ICE-driven generator is being confined within the vehicle hood and is exposed to heating resulting from ICE operation, high compactness, totally enclosed construction, and suitable machine cooling arrangement become challenging targets the generator design must deal with. Due to unique characteristics such as higher torque per volume and higher efficiency compared to other machine topologies, the axial-field permanent-magnet machine topology was selected for a 15-kW-at-4500-r/min-rated generator prototype that would be utilized in a demonstrator of an HEV drive train. This paper describes the original solutions adopted for the design of such an HEV generator and reports experimental results taken from the prototype machine.     

Nonconventional three-wheel electric vehicle for urban mobility

This paper outlines the original solutions adopted for powering a nonconventional three-wheel electric vehicle. This is a lightweight vehicle for use in urban mobility with mission tasks such as 50 km/h cruising speed and 80 km range of autonomy. The propulsion system is based on a lead-acid battery-fed wheel direct drive. This is arranged with a 4.5 kW prototype of a slotless axial-flux permanent magnet machine, which has a total weight of 15 kg and is capable of 85 Nm continuous torque and 120 Nm peak torque over 2 min. The motor is totally enclosed in the single front wheel of the vehicle and fed through an IGBT bidirectional power converter, which allows the control of both motoring and regenerative braking operations. Design characteristics and experimental data taken from the prototype of wheel direct drive are given     

Analysis and comparison of a speed-dependant and a torque-dependant mechanical device for wide constant power speed range in AFPM starter/alternators

In this paper, two methods for flux linkage regulation in a starter/alternator with an axial-flux permanent magnet (AFPM) machine are proposed and compared. Desired regulation is achieved by two different mechanical solutions, each of them capable of modifying the amount of flux linkage through displacement of the two rotors in the AFPM machine. Constant power generation is thus achieved with very inexpensive devices that do not require external energy sources since energy in the airgap doesn't change. The main difference between the two proposed solutions is that the speed dependant device is ideally a constant voltage source while the torque-dependant device behaves as a constant current source. Even if some improvements are still needed, both devices introduce the totally innovative concept of mechanical flux weakening for AFPM power regulation in a wide speed range. Finally, the paper demonstrates that the introduction of these devices doesn't modify machine behavior in starting mode, so that the particular features of AFPM machines in terms of high torque density and overload capability remain unaffected.     

Basic principle and design criteria of axial-flux PM machineshaving counterrotating rotors

Axial-flux PM machines are particularly suitable for application in electrical drives devoted to ship propulsion, since they allow the elimination of the large-power gearbox used in conventional systems. In consideration of that, this paper deals with a novel slotless axial-flux PM machine topology which is characterized by the synchronous counterrotation of the two machine rotors. Such a new machine topology can find application in the direct driving of two counterrotating propellers, which may be used in ship propulsion systems to recover energy from the rotational flow of the main propeller slip stream. In this case, the use of an axial-flux machine having counter-rotating rotors allows an improvement in terms of weight and efficiency, since the epicyclic gear otherwise required for the motion reversal can be avoided. The paper discusses the stator winding arrangement which allows the opposite motion of the machine rotors and reports experimental results taken from a small-size machine prototype     

Axial-Flux Permanent-Magnet Generator for Induction Heating Gensets

This paper presents a single-phase slotless axial-flux permanent-magnet synchronous machine for induction heating gensets. A full-scale prototype of the machine (110 kVA, 400 Hz, 690 A) has been designed and subsequently analyzed through finite element analysis (FEA). Induced current distributions in the permanent magnets and in the rotors have also been calculated through FEA, showing that the resulting losses are kept at bay due to the low armature reaction. An effective way of achieving regulation of the power transferred to the load has been analytically derived. The prototype has also been built, and experimental tests confirm the aforesaid analyses.     

Low-cost compact permanent magnet machine for adjustable-speed pumpapplication

The variable-speed driven pump can result in significant energy conservation where reduced flow rates are required for long periods of time. In regard to adjustable-speed pump drives, one major contribution of this paper is the demonstration that a permanent magnet (PM) motor based on the slotless axial-flux permanent magnet machine (AFPM) topology can be a suitable candidate to advantageously compete with the induction motor for such a low-cost drive application. For the purpose of a cost comparison, the paper discusses design and construction of a prototype machine which has been conceived to replace a 1.2 HP induction motor being used in a standard adjustable-speed pump drive. Results taken from laboratory tests of the prototype machine are reported, together with an assessment of the machine manufacturing cost     

New mercury-gap ring-collector system for double-armaturegenerators

A mercury-gap ring collector (MGRC) for supplying current to the rotating armature of the double-armature synchronous generator is presented. The MGRC can be considered as a valid alternative to conventional collector rings with solid brushes. It offers several advantages over sliding contacts with carbon brushes, especially when the machine has high rating currents and high rotating speed. The design of a prototype is presented; the experimental tests are reported, and the MGRC is compared with a conventional carbon brush collector     

Experimental study on reducing cogging torque and no-load power loss in axial-flux permanent-magnet machines with slotted winding

The axial-flux permanent-magnet machine (AFPM) topology is suited for direct-drive applications and, due to their enhanced flux-weakening capability, AFPMs having slotted windings are the most promising candidates for use in wheel-motor drives. In consideration of this, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having slotted windings in order to achieve substantial reduction of both cogging torque and no-load power loss in the machine. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve offline modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs, and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.     

Axial-flux permanent-magnet motor for direct-drive elevator systemswithout machine room

This paper deals with design and construction of two twin prototypes of slotless axial-flux permanent-magnet motor drives jointly developed by SIMINOR Ascenseurs and the University of Rome for application in direct-drive elevator systems without a machine room. Each prototype of pulley-direct-drive motor is rated 5 kW, 95 rev/min, and has a shaft height of 380 mm and overall axial thickness of about 80 mm. Machine design based on unusual specification and original manufacturing solutions adopted for the proposed direct-drive elevator arrangement are discussed throughout the paper, including the leading dimensions and characteristics of the prototype motors. Finally, experimental results taken from the machine prototypes are reported