In 2015, the year after the signing of the Russian-Chinese gas supply agreement, the Amur gas processing plant project was launched in Russia, located in the Svobodny district of the Amur region, about 200 km from Heihe, China, the source of the Russian-Chinese gas pipeline to the east. It will have an annual raw gas processing capacity of 42 billion cubic meters and will be able to deliver 38 billion cubic meters of natural gas to China every year.
The Amur Gas Processing Plant project site is covered by snow and ice for half of the year, with a minimum temperature of -52 degrees Celsius and a permafrost layer of about 3 meters deep. The harsh environment makes the construction of the site very difficult and places higher demands on the reliability and operating environment of the equipment. In this project, ABB will provide 10 explosion-proof motors with ultra-low temperature design to ensure the motors can operate reliably under the harsh natural environment and ensure the stable transmission of LNG. The design and manufacturing of these 10 explosion-proof motors are done by the Shanghai plant, which is gradually coming in line with the market expectations in terms of delivery lead time, response time and cost performance.
The presence of flammable gases in the LNG transmission process requires the use of explosion-proof motors in petrochemical pump drives, which place the motor's electrically charged parts inside a special housing, thereby isolating the sparks and arcs generated by the electrical parts inside the housing from the flammable gases outside. At the same time, the special housing can withstand the explosive mixture into the housing by the spark, arc detonation of the explosion pressure without being destroyed, thus preventing the spread of the housing to the outside, to avoid the outside of the burning and explosion of more combustible gases or explosive mixtures, to ensure the safety of personnel and facilities in the operating environment.
ABB's explosion-proof motors AMD can be widely used in different countries and regions, through a reasonable design, the motor can be used in ambient temperatures of -55 degrees to -60 degrees, capable of extreme climate, and through effective temperature control, AMD motors can achieve the temperature level of T5, suitable for almost all hazardous gases.
What is the difference between synchronous motor and asynchronous motor?
First, Why is it synchronous and why is it not synchronous?
The stator windings of synchronous and asynchronous motors are the same, the main difference is the structure of the rotor. Synchronous motors have DC excitation windings on the rotor, so they need an external excitation power supply to introduce current through the slip ring; while asynchronous motors have short-circuit windings on the rotor and rely on electromagnetic induction to generate current. In contrast, synchronous motors are more complex and more expensive to build.
Both synchronous and asynchronous motors are AC-powered motors, which are powered by the 50Hz AC grid and rotate. Asynchronous motors are fed with AC power from the stator to produce a rotating magnetic field, while the rotor is induced to produce a magnetic field, so that the two magnetic fields act to make the rotor follow the rotating magnetic field of the stator and rotate. The rotor is slower than the stator rotating magnetic field, there is a difference in rotation, not synchronous so called asynchronous machine. The synchronous motor stator is the same as the asynchronous motor, but its rotor is artificially added to DC to form a constant magnetic field, so that the rotor will follow the stator rotating magnetic field together and synchronization, the beginning is called synchronous motor.
Simply put, the rotor of an asynchronous motor does not add DC excitation current, and the rotor of a synchronous motor adds a DC excitation current to make the rotor rotate at the same speed as the stator and rotor cutting magnetic field.
Second, the synchronous generator rotor why the DC excitation current, but not into the AC excitation current?
According to the consideration of industrial frequency 50HZ, the rotor can induce 50HZ potential in the stator winding by passing DC excitation current.
After the rotor is fed with AC excitation current, it can be decomposed into two rotating magnetic fields, forward rotating magnetic field rotating speed and rotor rotating speed iterative, induction of 100HZ potential in the stator winding; reverse rotating magnetic field rotating speed and rotor rotating speed offset, and the stator winding is relatively stationary, no potential is generated, but the stator flux has a DC component and may saturate.