The role of large air separation plant cold box

Almost all motors commonly used in the air separation plant are three-phase AC motors. Three-phase AC motor can be divided into asynchronous motor and synchronous motor. The rotating speed of the synchronous motor and the frequency of the power grid keep a strict relationship, namely: N = 60f/P in the formula P -- magnetic pole logarithm; f -- grid frequency, the normal situation is 50Hz; n -- motor speed, r/min. For example, for two-pole (P = 1) synchronous motor, the synchronous speed is 3000r/min; for four-pole motor, P = 2, n = 1500r/min. While the rotating speed of asynchronous motor is always less than that of synchronous motor, and it generates rotating torque by its phase difference. Asynchronous motor is most widely used. It consists of a stator and a rotor, and has a stator and a rotor winding respectively. The stator winding is made of copper (aluminum) wire with outsourcing insulation. With the difference of rotor winding, asynchronous motor can be divided into squirrel ...

When the general motor in the air separation plant is started, the current that the stator of the motor takes from the power grid is about 5 ~ of the rated current of the motor ~ 7 times. After starting the small motor for one or two seconds, the current decreases rapidly as the rotating speed of the rotor gradually rises; while the large motor needs more than ten seconds, even dozens of seconds before the rotor reaches the stable rotating speed. That is, until the start-up ends, the current drops to the rated value. If the starting current of asynchronous motor is high, what problems will it bring to the use? If this motor starts frequently when it is used, the motor will heat severely due to the influence of starting current, which will affect the normal service life of the motor. In addition, if the starting times of the motor used are not frequent, when its capacity exceeds 30% of the power transformer capacity, due to the large starting current, it will cause the overvoltage dr...