Novel interspersed windings to reduce space flux harmonics caused by fractional-slot of synchronous machine
Fractional-slot windings is widely used in synchronous machine due to give us more flexibility on selection of the number of slot at design stage. It is also known that fractional-slot windings produces additional harmonics compare to integral-slot windings. These harmonics may cause increasing of stray losses and stator core vibration This paper describes the result of space flux harmonics caused by fractional-slot windings and propose novel interspersed windings that reduces the even order and/or fractional number space flux harmonic components. The advantage of proposed winding was confirmed by using numerical analysis and experiment using model winding machine.
A.C. machine windings with reduced harmonic content
This paper describes a type of double-layer winding known as an interspersed winding, which may be used in a.c. machines to reduce harmonic components of induced e.m.f. or load m.m.f. The principles underlying the design of interspersed windings are described and compared with the standard analysis of conventional windings in terms of harmonic winding factors. Design and performance details are then given for a complete range of 3-phase interspersed windings covering equivalent values of slots/pole per phase from 4 to 9. It is shown that control of the largest low-order harmonics may be achieved with insignificant alteration to manufacturing methods, and this type of winding should therefore find useful application in large generators and motors where the reduction of stray load losses is an important consideration.
Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems
Abstract Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.