VII Международная студенческая научная конференция Студенческий научный форум - 2015

This text is devoted to research of influence of size of a gap in the asynchronous engine with a squirrel cage motor. The main objective is to describe how the choice of size of a gap influences the main power indicators and reliability of the electrical machine.

Asynchronous motors are the most common type of electrical machines used in the global industry. Their release in Russia makes some million pieces a year. They work in the most various conditions and often do not need special service for long time. Therefore, perfection of design, ensuring reliability and energy efficiency of motors of this kind is the main problem of modern electromechanical engineering.

Asynchronous motor of power of 30kW has a shaft height of 180 mm rotation. The magnetic system of the stator is stacked with 2013 electric steel sheets of 0.5 mm thick. A stator winding is two-layer concentric one.

Rotor with the closed grooves are spilled with aluminum and are also stacked with 2013 electric steel sheets of 0.5 mm thick.

The air gap in asynchronous motors determines many of its properties. In engines of small and medium power the air gap is usually a few tenths of millimeters. This gap provides decrease in the magnetic resistance of magnetic circuit of the machine, and, consequently, a decrease of the magnetizing of current required to create the magnetic flux in the motor. Decrease of the magnetizing current allows increasing power factor of the motor. Also optimal choice of air gap affects the reliability of the asynchronous motor.

While choosing an air gap some contradictory tendencies may appear. The minimum air gap leads to decrease in the current idling of the engine and increase the power factor. However, at small air gap additional losses in the surface layer of the stator and the rotor, the additional moments and noise of the engine increase. Owing to growth of losses the efficiency decreases. Therefore in modern series of asynchronous motors the air gap is chosen somewhat larger than is required for mechanical reasons that the rotor is when working does not touch about stator. The stable size of air gap is provided with strict compliance of technological process of production of the making assembly units and details (boards, beds, cores, caps, rotors).

As a result of this work the asynchronous motor with specification and requirements of state standard specification was designed. Change of the air gap influences parameters and characteristics of the motor, especially power factor and reliability of the machine. Therefore, it is necessary to observe requirements to manufacturing techniques of the engine and at a design stage to choose an optimum air gap.

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