Most popular foreign companies challenge high volt

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Many foreign companies "challenge" high-voltage motors

the latest AC synchronous motor can work under the input voltage of 70 kV and can be directly connected with the power transmission line of the power industry, thus bringing other benefits while reducing energy consumption

imagine that if the motor can be directly connected to the electrical distribution line, it can greatly save energy, reduce heat consumption and power consumption, and do not need to install expensive transformers and related distribution equipment that need daily maintenance. Higher output voltage also means smaller output current at the same output power

you might say that this kind of motor is out of reach? In fact, one manufacturer has produced this kind of motor and successfully deployed two such devices in a harsh industrial environment. At the same time, other motor manufacturers are also considering launching their high-voltage products

earlier, abb automation technologies AB (Sweden) developed a generator that can generate high voltage and directly transmit electricity. On this basis, abb introduced a new type of very high voltage (VHV) AC synchronous motor, which can work in the input voltage range of 20~70 kV. ABB's very high voltage "motorformer" motor has the dual functions of transformer and motor, and eliminates the need to install intermediate transformers. The design is applicable to four pole and six pole motors. Without speed adjustment, the synchronous speed of four pole motor can reach 1500/1800 rpm at 50/60 Hz power frequency. (now, abb has licensed its Powerformer generator technology to ALSTOM, which has installed several sets of generator equipment.)

The motorformer motor was first used to drive a compressor of an air separation unit located on the west coast of Sweden. According to abb, the active power output of the synchronous motor is up to 6.5 MW, which is directly connected to the 42KV bus, which can save 25% energy consumption for the factory. Since the very high voltage motor was put into operation in 2001, no accidental shutdown accident has been reported

Statoil of Norway has installed two sets of motorformer motors on its "Troll a" oil and gas production platform in the North Sea. These two sets of motors are used in a compressor module with an output power of 40 MW and a supply voltage of 56 kV. This application also includes the variable speed control of the motor. The two sets of motors are scheduled to be commissioned in autumn and winter 2004 and are expected to be put into production in the second half of 2005. At present, ABB's very high voltage motor is unique in the market, and no other similar products have been introduced. Many manufacturers, including abb, can produce large conventional AC motors (synchronous motors and induction motors), but the maximum input voltage of these products is only 15 kV

synchronous motor, not induction motor

the development direction of motorformer motor tends to synchronous motor, not induction motor. Because compared with induction motor, synchronous motor has the following advantages: higher power level (the output power of synchronous motor can be greater than 100 MW, while induction motor is only 20 MW); Higher efficiency; Wider air gap, easy to design; It has the ability to control reactive power. Johannes ahlinder, ABB's AC motor business development manager, said, "induction motors always consume reactive power as the negotiation of this reorganization enters a critical period." For the main industrial areas with a large number of large motors starting in a working cycle, the control of reactive power is an important issue to stabilize and protect the electricity in the area

surprisingly, the design of motorformer is based on traditional synchronous motor technology. These include mature motor components, such as the same salient pole rotor and traditional bearings (see section). According to ahlider, this method provides a lot of experience for the design of motorformer, and improves the confidence of product reliability. The breakthrough of motorformer lies in the design of its stator

winding design is the key

abb adopts a unique design in the stator winding and stator core slot of its motorformer motor, and has carried out a lot of analysis, simulation and testing in the cable design, including electromagnetic field finite element analysis, thermal simulation and computational fluid dynamics modeling. The efficiency of raw materials in the production process. However, the rule used to determine the magnetic flux density of stator core is the same as that of conventional motors, which limits the uncertainty in product development

Ahlider points out that the insulation system used in conventional motors has a voltage limit of 15kV, which can be extended to 22~25 kV with the help of special design technology. He said, "if you want to exceed this limit, it is impossible to design the stator winding with traditional technology. The cylindrical design of motorformer cable can produce uniform electric field strength, which can effectively improve the voltage level compared with the traditional rectangular winding." The traditional winding shape will lead to uneven electric field distribution. For example, under high voltage, the electric field will be concentrated at the corners of the conductor

the cylindrical cable has a solid dielectric spring fatigue testing machine with cross-linked polyethylene (XLPE) insulation material, which should be carefully selected, but the metal shield is not used. At present, the stator can withstand 70 kV power supply voltage, and the cable design can gradually reach the limit of 150 kV as required. Ahlider said, "from an economic point of view, the low-end voltage is about 20 kV, which depends on the load."

the physical size of the motorformer depends on the output power, and even parameters such as the center height of the motor shaft also depend on the actual application. Although the overall volume of the motorformer is larger than that of a conventional motor with the same rated power, the total installation space of a very high voltage system (motor and circuit breaker) is smaller than that of a conventional system with transformer and related equipment

design challenges

the starting of large-scale high-voltage motors will consume a lot of energy and cause temporary interference to the power supply of electricity and nearby electrical equipment. ABB has successfully developed a delayed start technology to avoid power supply interruption. This technology uses a reactor to extend the starting time by 20 seconds, and increases the capacitance to consolidate the electricity during starting

in order to meet the temperature limits of XLPE insulation cladding and wire wound stator, the high-voltage motor needs to adopt a reasonable cooling mode - air cooling mode at low power and water cooling mode at high power. The stator structure of motorformer is equipped with the above two cooling methods

abb believes that there are almost no application limitations for high-voltage motors. Ahlider said, "any limitations are related to the development of conventional products, such as the design of rotors." However, cable temperature is still considered a limiting factor, especially in high heat environments and where water cooling is not feasible

control engineering has asked several major motor manufacturers for their views on high-voltage motors. Most manufacturers didn't reply. One of them replied that it had investigated high-voltage motor technology, but it was finally determined that it was not a "feasible choice for future business". TECO Westinghouse and Emerson motor technologies have fed back some valuable views. Please browse for details

application prospects

according to ahlider, high voltage motors are currently mainly used in offshore oil production industry, and a major trend in this industry is to replace gas turbine transmission equipment with electronic drivers. Its application fields include generator sets used in offshore power stations such as offshore compressor drive and floating production and storage system (FPSO). The power generation system of these similar ships can supply power to the surrounding offshore oil production platforms after being connected with the appropriate power transmission system

Ahlider said, "from a broader perspective, high-voltage motor technology is applicable to any field where traditional synchronous motors are currently applied, including pump motors, refiner motors used in pulp and paper, and motors used to drive compressors in air separation, fans, extruders, and gas/steam turbine driven generators."

of course, high-voltage motors are not omnipotent, but their application prospects will be broader. The related technology of improving the temperature level of cable winding is constantly improving. Ahlider explained, "in the troll oil and gas field project of Statoil, the very high voltage motor needs to be controlled by variable speed drive, and the high voltage motor technology directly leads to the emergence of new solutions."

at present, abb plays a pioneering role, fully supporting and promoting this exciting new technology. The practical application of high-voltage motors in North America and the launch of similar products by other manufacturers seem to be in the near future

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how high is the "high voltage"

you may say that nothing is simpler than defining the voltage range of a motor. However, in fact, there is no unified definition of the high voltage range of motors

for different users, high voltage has different definitions, which depends on many factors such as industry, geographical location, application environment, standard setting organizations and associations. For example, at least one manufacturer refers to its 100~240 V AC motor as "high voltage motor". This may be for safety reasons, in order to comply with the 75V threshold set in the EU low voltage directive. Similarly, some servo motor suppliers proudly claim that their 460 V products are "high voltage equipment"

in the United States, the national electric code defines voltages above 6001v as high voltage, and 601v to 6000V as medium voltage. Europe adopts different standards. IEEE STD. 100 defines the high voltage range in the power system between 100kV and 230kV, and EHV is defined as more than 230 kV. The IEEE STD. 100 standard also defines the relevant voltage range of the transmission line

high voltage is also applied in the field of power transmission and connecting lines, with the relevant voltage range exceeding 500 kV, and recently even rising to 765 kV. At the same time, ultra high voltage (UHV) transmission lines have been used in 1.1 MV power transmission

abb defines motorformer products with input voltage of 20~70 kV as very high voltage (VHV) motors, which conforms to the definition of very high voltage in this paper

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