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工矿企业的异步电机取自电力系统的无功占70％以上。为了减少电网输送无功功率,都广泛采用电容器来进行无功补偿,以提高企业的功率因数。据统计,象Y系列这类小型异步电机要消耗我国发电量的40％。因此,小型电机的直接无功补偿,对节电、改善受端电压,提高电力系统的稳定性,都具有现实意义。 (一)补偿容量的确定及适用范围 当电容器与电动机直接连接,而电容器与电动机共用一套控制、保护装置,并利用电动机定子绕组作为它的放电回路时,为了防止电动机自激而产生的过电压,无功补偿电流不应大于电动机的空载电流。一般取电动机的空载电流的90％,电容器的容量按下式计算:
Induction motors of industrial and mining enterprises take more than 70% of the reactive power from the power system. In order to reduce the reactive power transmission grid, are widely used capacitors for reactive power compensation, in order to improve the enterprise's power factor. According to statistics, such as the Y series of small asynchronous motors to consume 40% of China's power generation. Therefore, the direct reactive power compensation of small motors is of practical significance for saving power, improving the receiving voltage and improving the stability of the power system. (A) Determination of the compensation capacity and the scope of application When the capacitor and the motor directly connected, and capacitors and motor sharing a set of control and protection devices, and the use of motor stator winding as its discharge circuit, in order to prevent the motor from self-excitation generated Voltage, reactive power compensation current should not be greater than the no-load current of the motor. Generally take the motor 90% of the no-load current, the capacity of the capacitor is calculated as follows: