VII Международная студенческая научная конференция Студенческий научный форум - 2015

Asynchronous motors are the most common type of electric motors. They are currently consuming about 40-50% of the total electricity generated. Their set capacity is constantly increasing. They work in a variety of conditions, often for a long time without special maintenance, without any care. Several million units per year are released in Russia.

I designed the induction motor with squirrel cage following the procedure described in the book of professor I. P. Kopylov. The result is a motor that meet technical requirements, the requirements of GOST and technical requirements. Starting and performance characteristics are shown in Figure 1 and 2.

Figure 1 - Starting characteristics of the induction motor	Figure 2 - The performance of the asynchronous motor

Depending on the load of the industrial enterprise the voltage at the terminals of the receiver power is not constant and may differ from the nominal. Supply frequency may also vary. These changes cause deviations in the motor. It is important to consider the impact of voltage and the frequency of the supply voltage to the characteristics and parameters of an induction motor.

The research work is carried out by calculation of the engine at the rated operation and during the change in the magnitude of the supply voltage range of 220 ± 10%, and when changing the frequency of the supply voltage in the range of 50 Hz ± 10%. Calculations are carried out in an environment Microsoft Excel. As a result, dependence of parameters and characteristics of the engine on the magnitude of the supply voltage and frequency is found out.

When voltage is reduced by 10%, the consumption current increases (the current of the stator winding), consequently winding losses are increasing. Overheating of the stator winding is above the norm. If the motor runs for a long time at reduced voltage, then due to the accelerated depreciation of insulation life of the motor is reduced.

When the voltage is increased by 10%, current consumption is reduced (current stator winding), therefore losses in the winding are reduced. Multiplicity of starting current is above the norm (7.5).

If the frequency is reduced to 10% the current consumption increases, resulting in increasing of coil losses. Losses have also increased. Overheating of the stator winding is above the allowable.

As the frequency is increased to 10%, the current consumption significantly decreases, therefore, overheating of the stator windings does not substantially vary. Iron losses are reduced. It can be concluded that the value of the frequency of the supply voltage is not harmful to asynchronous motor.

Based on this work, we conclude that the change in voltage and frequency supply greatly affects the motor performance parameters and, therefore, must comply with the quality requirements of electricity set in GOST 13109-97. This Standard establishes normal and maximum allowable voltage deviation Uynor = ± 5%, Uypred = ± 10% of nominal value, and the normally allowable limit values and frequency deviation equal to ± 0,2 and ± 0,4 Hz respectively.

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