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Aluminium smelters with electromagnetic stirrer
 the principles of Electromagnetic Stirrer
“Stirring” aluminum smelting process is an important process measures. Mixing full or not directly determine the aluminum products’ quality. Mixing way has artificial stirring, gas stirring, mechanical agitation, electromagnetic stirring etc. with electromagnetic stirring because of its fully mixing, simple operation and grew in popularity. Inductive electromagnetic stirring device is a kind of application principle of electromagnetic induction and produce a magnetic field in the role of molten aluminium liquid so that melting liquid has regular exercise equipment. In the electromagnetic stirring subject device-to low frequency current smes of sensors, in order to form the traveling wave alternating magnetic field, melting liquid in the influence of the magnetic field of emf and current, the induced current and magnetic fields interact to produce the electromagnetic force, make the melting liquid regular exercise, in order to achieve the purpose of mixing. By changing the direction of the field and the traveling wave strength, can effectively regulate the melting liquid mixing direction and stir intensity.
 application of Electromagnetic Stirrer
In the primary aluminum used in the production process of electromagnetic stirring technology the most main purpose is to make the aluminum alloy melt liquid components uniform, and on the waste recycling technology’s main purpose is to improve the melting effect, to reduce the loss and increase casting yield. Of course, since the noise components of the waste aluminum was more complex, long time mixing for composition adjustment and composition of the improved uniformity is particularly important. We shall, according to the different purpose reasonable setting of electromagnet stirring device installation position sensors, either party furnace, the furnace, single room or double room furnace, the installation of sensors can kind of wan, buy the installation is mainly used for the new furnace form or depth of molten pool in the production process change the big furnace, this form melting liquid depth change effects and can achieve good mixing effect, in waste recycling aluminum furnace installation position to deviation furnace center, so can form the whole furnace big, help to fast melting scrap aluminum. Sensors installed side is mainly used for old furnace way transformation and molten pool depth in the production process change less than 200 mm.
 compisition cf the Electromagnetic Stirrer
Electromagnetic Stirrer is composed of AC-DC-AC inverters, inductors, pure water-cooled devices (water-wind type)， functional trolley and appurtenances. The function of AC-DC-AC inverters is to convert 50/60Hz industry frequency alternate current (AC) into a 0.5 ~ 5.0Hz, 3-phase low-frequency power. The power through sensor coil, will produce a traveling magnetic field, which penetrating stainless steel plate of the bottom of furnace and lining effect on molten aluminum, make molten aluminum regular movement, finally achieved the purpose of even stirring. By changing the voltage, frequency and phase of the variable frequency power supply, you can change the magnitude and direction of the stirring force.
With the economic development our country is from a big to a strong aluminium country, both from the product categories and product quality are required to have a qualitative leap, to do a good job, must first sharpen his device, so our furnace technology changes with each passing day, form a complete set of equipment technical also requires synchro. “Energy saving, green environmental protection” become the core topics in today and forever, so electromagnetic stirring on the original application effect to really make a big improvement that is energy saving from the device itself, if electromagnetic stirring in their own breakthrough on core subject equipment first, that are inductors and power supply.
The core of the inductor is efficiency of magnetic field, to enhance the efficiency of the magnetic field means that the input power reduction, the two key factors directly effecting the efficiency and magnetic field, one is the magnetic medium, the other is the winding structure. The magnetic medium (medium flux loop), including the inductor iron core, bottom material and molten metal. We use silicon steel sheet in the inductor’s iron core, because of its high saturated magnetic induction intensity, less wastage, at present in the applications of magnetic materials industry is the preferred material. Bottom material used is stainless steel and refractory material, relative permeability of these two kinds of material is 1, no matter from furnace body structure strength and magnetic circuit are irreplaceable, so from the magnetic circuit of the sensor material, combined with refractory silicon steel sheet or stainless steel window from the technical point of view is irreplaceable, it is difficult to break.
The advantages of horizontal concentrated winding: Facilitate the installation of the winding and fixed, and vertical effective magnetic field and have high utilization rate, and when destructive occurs in the winding is convenient for application field to replacement and maintenance, will not directly affect the customer production.
The advantages of vertical concentrated winding: Can narrow the width appearance sensors then narrow stainless steel window size. Shortcoming: This way for electric winding, due to the vertical direction of main magnetic circuit level stress is bigger, bring difficulty for winding is fixed, the short circuit failure rate will increase between the layers and turn-to-turn, this kind of structure is not convenient to application field of replacement and maintenance.
So in the new type of AC-DC-AC inductor’s structure, our company still uses the horizontal concentrated winding structure.
To sum up, for the inductor, no matter from magnetic media or winding structure, at present it is difficult to have a big span to improve the efficiency of the magnetic field, in order to reduce the input power to achieve energy saving effect. Now from technical point of view can really solve electromagnetic stirring of energy conservation and environmental protection technology core is how to reduce the equipment installed power, improve the efficiency of power supply, improve the power supply output waveform to enhances the working efficiency of the sensor, this prompted aluminium smelters electromagnetic stirring to solve the problem of power generation fundamentally, that is how to make domestic AC-DC-AC power supply applied to aluminium smelters electromagnetic stirring.  Six Generation AC-DC-AC electromagnetic stirrer
The development of electromagnetic stirrer power supply
Characteristic: Silicon controlled core device Industrial grade DSP core components is IGBT
The circuit configuration is a half bridge structure. Using PWM + PWM four-quadrant vector control structure
Big installed power Installed power is nearly one third of AC
Power factor is less than 0.4 Power factor is greater than 0.96
Big harmonic component Harmonic component approximate to 0, green environmental protection
Isolation transformer: The full name is electrical safety isolation transformer, the most important application purpose is to insulate the equipment power system and electrified wire netting in order to make electricity and personal safety; secondly, using the high frequency characteristic of the core has inhibitory effect on high frequency harmonic; so, using isolation and structure of the power source have nothing with harmonic size, directly related to electrical safety, we can’t at the cost of electricity safety to reduce the equipment manufacture cost.
functional descriptions of AC-DC-AC source
Inverters of IDEA ELECTRIC adopt PWM+PWM (four quadrant vector control structures) AC/DC/AC converter technique and by adjusting software and hardware they can make stirrers’ power with low-frequency and high-inductance reactive load. With the advancement of converter technique, power devices of transducers have undergone the development history from SCR, GTO to IGBT, and AC/DC/AC control manner develops from the initial constant V/F control to vector control as well. However, advancement of power transformation technology and wide application of power converter also bring hosts of shortcomings whose public hazards—electromagnetic interference and harmonic pollution have become well-known social problem. Main circuit enters the general AC-DC-AC voltage source inverter through three phase un-controlled full wave bridge rectifier and charges the filter condenser of CD-link. And then it is input to the load through the inverter controlled by PWM. Though this kind of circuit has the Merit of low cost, simple structure, and high liability, it has hosts of shortcomings such as low power factor, harmonic pollution and non-renewable of energy etc. due to the application of three phase uncontrolled full wave bridge rectifier.
PWM+PWM (four quadrant vector control structures) converter technique breaks the unified structure of former converters. The system's power factor up to 1 can be realized through adjusting software and hardware and using accessories like reactor by PMW rectifier and PWM inverter. Thus eliminating harmonic pollution, green, four quadrant load operation, bi-directional energy transfer, efficient energy transform, and meeting the needs of low-voltage large-power and high-voltage large-power become the application hotpots. It injects vigor and vitality into converter technique and leads the latest trends of developments of converter technique.
PWM+PWM (four quadrant vector control structures) converter power source is constituted by PMW rectifier and PWM inverter. The former adopts full control switch IGBT and introduces PMW converter technique to control the rectifier. Compared with non-controlled or phase-controlled rectifying power source, PMW rectifier has the following better performances: First, it realizes the control of grid-side unit power factor and sine-wave current. In an ideal case, the current in a back-to-back PWM converter power source is a sine-wave current, consistent with the input voltage. Its power factor is up to 1 and the harmonic distortion of input current is almost zero. Second, PMW rectifier can operate in both rectifying and inverting status, and can make full use of regenerative energy by realizing bidirectional energy-transform. Third, it possesses the advantageous output, especially the fast dynamic responses. In addition, compared with traditional rectifying power source, it has the merits of efficient energy saving, quickly adjusting, and KN-three-phase self-balancing. It can also eliminate hidden dangers caused by current loop fault of AC-AC rectifiers, which is composed by thyristors.
Our company’s IDEA - 1001 series of products use ark structure, make up with control cabinet, rectifier cabinets, inverter cabinet.
3.The power supply’s technical characteristics Support for 380 v, 480 v, 690 v, 1140 four voltage grade;
Support two quadrant operation, four quadrant operation;
Support the VF geometric and separation, senseless vector control, speed sensor vector control;
Support power units in parallel, Up to eight units in parallel at most;
Support the parallel between system: Rectifier and inverter through the point-to-point communications more than a master in parallel mode.
Support failure of unit heat exits;
Support 4 kinds of communication functions can be used at the same time, Industrial ethernet, Profibus-DP、CAN and Modbus-RTU;
Rich resources of users (4-way AI, 4 DI AO, 15 road, no.11 DO, 2 PG, 3 PTC).
4.Superior technical performance
Four quadrant operation (rated) under the condition of the power factor of system (±0.99), grid side current harmonic is less than 5%, IGBT rectifier of busbar voltage fluctuation is less than 2%;
Vector control, have 2 times speed torque output capacity;
Frequency output 0-5HZ is continuously adjustable;
Power unit parallel uneven flow degree is less than 5%;
System parallel’s uneven mobility is less than 5%;
The runtime’s noise is less than 80B.
5.Application Characteristics
a. The energy feedback technology in the rectifier side load factor around 40%,the system power factor can reach more than 0.95; which can reduce the cost of power grid side power supply transformer capacity, also help users to save a reactive power compensation equipment investment.
b. The four quadrant feedback technology makes high power frequency conversion power supply for grid side current total harmonic pollution is greatly reduced, when rectifier side load factor is more than 60%, total harmonic current is less than 5%, green and environmental protection.
c. The four quadrant converter bus voltage and the output voltage controlled continuously and smoothly (affected by factors such as power grid voltage fluctuation is small), overcome the disadvantages of the AC frequency conversion or the ordinary two quadrant inverter output voltage affected by power factors such as fluctuations in large, metal smelting effect.
d. Support four kinds of communication mod, such as Profibus-DP, Modbus-RTU, CAN, Industrial Ethernet, convenient for industrial field a variety of applications.
e. The special function of VF separation, Solved the problem of big capacity of electromagnetic stirring special work load of active defense security parking.
f. The reasonable braking system configuration and special software processing meeting the sudden power failure in the operation of the special conditions such as electromagnetic stirring system and reliable safety shut off, to avoid the traditional AC-AC frequency conversion power supply or AC-DC-AC 2 quadrant inverter power under the condition of the limitation of the airline.
g. With same modular parallel structure, easy to install replacement and maintenance.
the parameter list of Six Generation AC-DC-AC electromagnetic stirrer
 The water-wind tipe:Pure water is forced cooled by fan through the heat sxchanager.
Constitution:a plate-fin heat exchanger,a pump group,a water tank,an ion exchange tank,a channel valve and electrical control units,etc.
 The water-water type:Pure water is forced cooled by external circulating water through the heat exchanger.
Constitution:a removable plate-type heat exchanger,a pump group,a water tank,an ion exchange tank,a channel valve and electrical control units,ect.
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