Integrated approach for auto-adaptive synchronous motor winding

The intrinsic characteristic of a permanent magnet synchronous motor is defined by its internal dimensions, its material properties, as well as the power supply used in conjunction with the motor. When an extended operating range is desired but the electronics are limited, motor manufacturers face a problem. Furthermore, when different operating points are needed -e.g. a low torque with a high speed as well as a large torque at a lower speed- the used drive system is oversized so that all operating points are included in the motor's characteristic. Therefore, this thesis aims to find a solution to obtain an extended operating range while considering the use of limited electronics. In addition, the proposed solution must be embeddable into the motor. A survey of possible solutions allowing the increase of the motor's intrinsic characteristic is presented. Among them, the dynamic winding reconfiguration is chosen because it allows an increase in torque and in speed while having restrictions on the electronics. This reconfiguration is performed by using switches. As the connections between the coils of the winding will be reshaped, coils can be placed in parallel. Depending on the geometrical distribution of these coils, circulating currents may appear, which in turn will be generating unwanted losses. Therefore, a study of the spatial distribution of the turns is undertaken demonstrating that these currents can be significantly reduced without adding complexity to the winding manufacturing. Considering the integration of the switching system and the alternating current that will run through it, the MEMS (Micro Electro-Mechanical System) relays are favored because of their ease of use, their galvanic separation when they are open, but especially thanks to their separation between the control command and the signal, which removes all the floating voltage issues. In order to reduce the contact resistance, the design of the relay is based on an innovative system of double springs combined with variation of the flexural rigidity of the contact structure. In addition, the influence of microfabrications tolerances is considered in the design. A novel manufacturing process flow has been specifically developed to manufacture the relay in a cleanroom environment. The prototypes obtained and the mechanical and electrical characterizations performed on them confirmed the feasibility of the design and the manufacturing methodology. From then on, the control allowing the winding reconfiguration is studied. The latter focuses on slotless permanent magnet motors. Their low inductance implies rapid current variations and by extension rapid torque variations as well. The proposed methodology explores the transient regime from one configuration to another and is based on a fine control of current amplitude and the commutation angle. Numerical simulations and experimental results confirm the accuracy of the proposed approach.

Perriard, Yves
Köchli, Christian
Lausanne, EPFL

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 Record created 2018-09-24, last modified 2020-04-20

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