1T/750KW/500Hz melting furnace project

First, the program description

1. System total plan

Our company refers to and integrates the advantages of medium and medium frequency induction melting furnace at home and abroad. Based on the principle of reasonable structure, advanced technology, practical and reliable, and convenient maintenance, the 1T intermediate frequency constant power digital control electric furnace is produced . Compared with ordinary lines, the energy saving effect is obvious. It can save about 5% of electricity , because the connection is very small, the failure rate can be reduced by 90% , and the commissioning and maintenance is simple.

Second, the main technical parameters of 1T/750KW melting electric furnace equipment ( 12 pulse aluminum shell)

Remarks:

1 ) Adopt 6- phase 12- pulse double rectifier control system.

2 ) The use of a fully enclosed cooling tower can improve the cooling effect of the system and the service life of the equipment without the need to build a pool.

3 ) Since 2006 , our company has exported to Sweden, Norway , and Latvia , and exported to Africa , Southeast Asia and other countries .

This set of intermediate frequency smelting equipment complies with GB5959.3 "Safety of electric heating equipment Part III Special requirements for induction and conductive heating equipment and induction melting equipment", GB10067.3 "Basic technical conditions of electric heating equipment Part III Induction electric heating equipment" and JB4280 "Intermediate frequency coreless induction furnace" requirements.

III . 1T/750KW medium frequency melting furnace project project quotation ( 12 pulse aluminum shell)

4.Vulnerable spare parts and spare parts

Five, the main components supporting manufacturers (for famous manufacturers)

1. Power cabinet:

(1) Main circuit breaker Shanghai People's Electric Appliance Factory or Delixi DW Series

(2) Rectifier thyristor          Hubei Xiangfan Power Electronics Group Co., Ltd.

(3) Inverter thyristor          Hubei Xiangfan Power Electronics Group Co., Ltd.

(4) The main control board is homemade

(5) buttons, indicators, etc.    Shanghai Second Industrial Electric Appliance Factory

(6) Protecting the thyristor's resistance and capacitance    794 factory and 795 factory

(7) copper row    Luoyang Copper or Zhejiang Shangyu Copper Material Factory

2. Electric heating capacitor     Xinweijiang Capacitor Factory "Weiwei" brand           

3. Furnace: ( 1) Induction coil copper tube Luoyang copper or Zhejiang Shangyu copper factory

(2) Silicon steel sheet Wuhan Iron and Steel Company

(3) Cylinder Sichuan Changjiang Hydraulic Parts Factory or Shanxi Yuci Group

4. Hydraulic system: (1) Hydraulic components Beijing Huade Hydraulic Group Co., Ltd.

(2) Oil pump Shanxi Yuci Group Hydraulic Factory

(3) Motor Xi'an Motor Factory

5. waterway system:  

( 1 ) FBT closed cooling     self made      

Seven, power transformer introduction

This equipment adopts special rectifier transformer (designed according to high altitude, the latter equipment is designed and produced according to high altitude)

Transformer technical parameters rectification :

Model: ZSS-800/10 one (for 1 ton melting furnace)

Rated capacity: 800KVA

Rated voltage: 10KV ± 5%/750             

The transformer used in the IF solid power supply is used to reduce the voltage of the 10 kHz high voltage to the medium frequency power supply used. This equipment uses a dedicated rectifier transformer for oil immersion. The rectifier transformer is model ZS- 125 0 KVA. Primary voltage 1 0KV, secondary voltage 1000 V. The short-circuit impedance of the rectifier transformer ranges from 6% to 8% . In the high-voltage side of the transformer provided with no-load tap changer manually, can --5%, 0, + 5% third gear regulate the output voltage. The power transformer is equipped with a gas relay and an oil temperature meter, and its output is interlocked with the high voltage switch cabinet. When the transformer has a gas alarm or the oil temperature is too high, it automatically cuts off high

The power supply uses a horizontal power control system. It is used in the smelting, heat preservation and induction heating equipment of various metals. This technology has reached the domestic leading level.

The power control board is a fully integrated control board of the single board machine. It adopts digital triggering and has high reliability, high precision and adjustment.

The maintenance is simple and convenient, the debugging is easy, and the relay components are few.

3 , the main circuit incoming line can be divided into phase sequence (phase sequence automatic adjustment).

4 , advanced constant power zero-pressure sweep start technology allows the operator to achieve 100 % successful start without having to select the starting voltage and starting frequency .

5 , inverter control reference US ABB company, Pillar , Ajax company, Japan Fuji Electric and other foreign advanced control technology, has a strong anti-interference ability.

6. Automatically follow the load change, with non-faulty automatic restart capability and automatic power adjustment function during operation.

7. It has ideal interception, interception, precise off time or inverter angle control to ensure reliable operation of equipment.

8. With perfect multi-level protection system (water pressure, phase loss, undervoltage, overcurrent, overvoltage, off time, straight through, operation interlock, etc.), it has high frequency conversion efficiency, and 1000HZ and below is greater than 94 %.

9 . Main circuit parameters:

1 ) Protection and temperature control

·Main circuit short circuit protection (circuit breaker, main control board protection)

·Main circuit phase loss protection (main control board protection)

·Cooling water pressure low protection (main control board protection)

·SCR overvoltage protection (main control board protection)

·SCR overcurrent protection (main control board protection)

·Inverter thyristor current rise rate high protection (current transformer protection)

·Inverter thyristor commutation time insufficient protection (main control board protection)

·Inverter thyristor reverse shutdown voltage time insufficient protection (main control board protection)

· Power supply cooling water temperature, pressure, induction coil water temperature, water pressure and cooling water flow protection have perfect detection and protection system settings.

·Blowout furnace protection (other special circuit and main control board are combined with trivial protection)

· Power supply cooling water temperature and pressure protection.

2 ), display measuring instrument: on the intermediate frequency power cabinet: DC current meter, voltmeter, intermediate frequency voltmeter, power meter, frequency meter.

3 ), compensation capacitor: capacitors all use new large-capacity non-toxic medium water-cooled intermediate frequency capacitor

c) furnace body part

1 . Furnace characteristics

The mechanical part of the medium frequency induction furnace is composed of a furnace cover, a furnace body, a fixed frame, a water and electricity introduction system, a hydraulic device, and the like.

Furnace body: induction coil, yoke, hob and furnace alarm device

1 ) Induction coil

·The induction coil should be fired with an oxygen-free copper rectangular thick-walled tube with a purity of 99.9% . The thickness of the tube wall is uniform, and the water-electric joint is durable and easy to disassemble.

· There are water-cooled coils on the upper and lower parts of the induction coil, which is the axial heating of the lining material to extend the service life of the furnace lining.

· In order to strengthen the insulation of the induction coil, a high-strength insulating resin should be sprayed on the surface of the coil, and refractory clay (refractory degree: 1800 °C) is applied in the induction coil and between the outer wall and the crucible. Due to the high insulation and thermal insulation properties of the refractory mortar, the induction coil is protected from damage when the lining is damaged.

2 ) Through years of design and use, it has accumulated certain empirical data on its aspect ratio ( H / D ), and has different height-to-diameter ratios for sensors of different tonnages. The height-to-diameter ratio of computer optimized design has greatly improved its Electrical efficiency.

3 ) The sensor material is made of copper T2

A , copper content  99 . 95 %, B , tensile strength   220K g / c m  

   C , stretch rate   45 %,   D , hardness  HB35

4 ) Sensor design:

The large-tonnage sensor designed by our company adopts the parallel connection of upper and lower sections to improve the electrical efficiency of the inductor, which is conducive to the production and improvement of mechanical strength, and can reach full power operation under the condition of half furnace and full furnace. The dielectric strength is applied with rated voltage plus 1000V without breakdown and flicker. The surface coating lacquer is silicone enamel 167 , the insulation resistance is rated voltage below 1000V , not less than 0. 5 M W ; when the rated voltage is above 1000V , not less than 1M W .

Produced in strict accordance with the process requirements of the sensor.

2 , hob: (steel furnace shell)

    On the basis of the original Soviet-style structure, the movable hob and the fixed bracket absorb the advantages of foreign countries such as the United States, and the British Renault. The squirrel cage is open, compact, stable, easy to dissipate heat, and easy to maintain.

Yoke: (steel furnace shell)

  The yoke is made of high-quality high-lying silicon steel sheets ( D330 or D43 ). The yokes are clamped with new stainless steel. They are distributed on the outside of the coil and account for more than 65 % of the outer surface of the coil . It is mainly magnetic shielding. The magnetic flux outside the inductor can be concentrated along the yoke with the smallest reluctance to constrain the magnetic flux of the inductor to divergence outward, improve the electrical efficiency of the furnace, and also act as a fixed and supporting inductor. Gray alkyd enamel coating layer, the insulation resistance of not less than 0. 5M W. Yoke of high permeability with a thickness of 0.30-0.35 mm cold-rolled silicon steel, the maximum magnetic reduce losses and improve the efficiency of the electromagnetic coupling.

4 . Leakage alarm device

1 . During the operation of the 感应-type induction furnace, cracks are often formed in the lining due to various reasons, resulting in a furnace accident. If such an accident cannot be found in time, the lighter is to damage the insulating layer of the induction coil and the yoke. The heavy one is that the copper coil of the induction coil is burned out, and the high-temperature molten iron and the cooling water of the induction coil are in contact, causing serious equipment accidents. It even caused an explosion that endangered personal safety. In order to ensure safe production and prevent the occurrence and expansion of leakage accidents, it is necessary to set up a leak alarm system. The alarm device must send a leak alarm signal before the molten iron reaches the sensor. It can judge the severity of the leaking furnace, properly handle the molten iron in the furnace, and minimize the damage caused.

The leakage alarm device is not only a safety protection measure, but also helps to judge the use of the lining to achieve the purpose of extending the furnace age. Some furnaces have no leakage alarm device. After the furnace runs to a certain stage, it is difficult to determine whether the lining can continue. Use, but afraid of leaking the furnace, often ruin the furnace lining in advance, resulting in unnecessary waste of manpower and material resources.

Contact type leakage furnace alarm device works:

2 , the principle of contact leakage alarm device see the attached figure. A stainless steel wire is embedded in the bottom of the furnace as a bottom electrode (called the first electrode), which should be in good contact with the molten metal in the furnace. Another electrode (called a second electrode) made of a non-magnetic material (such as stainless steel foil, aluminum foil) is placed between the two layers of asbestos sheets inside the induction coil. The shape of the second electrode can be made into a fence or a dressing, and its height is slightly higher than the height of the molten metal in the furnace, and a short-circuit ring cannot be formed during installation. A low voltage direct current is applied between the two electrodes. Under normal circumstances, the lining material and the insulating asbestos board have a large insulation resistance. If it is a silica sand knot lining, the insulation resistance is in the range of 5~10 K Ω , and the current is very small ( about 10 mA or less at 30 VDC ), and Also more stable. When the metal liquid leaks into the furnace lining and contacts the second-stage electrode, causing the first and second electrodes to be short-circuited, the current suddenly increases. When the alarm set value is reached ( about 70~80 mA at 30V ), the alarm device sends a signal. And cut off the power.

This circuit is mainly used for leak alarms, but it can also check the grounding of the main circuit and the low resistance of the cooling water. The switches S 1 to S 5 are respectively closed to perform different inspection functions. Such as: S 2   , S 4 is closed, and the test rod is in contact with the metal in the furnace to check whether the first electrode lead and the entire control circuit and components are intact; S 2 , S 5 closed to check whether the metal touches the copper coil of the induction coil; S 1 , S 3 closed to check if the second electrode is grounded (grounding usually occurs at the lead line); S 1 , S 4 is closed, and the test rod is in contact with the furnace metal liquid to check whether the molten metal has hit the furnace shell; S 1 , S 5 are closed to check whether the main circuit is grounded; in the leak alarm state, S 2 , S 3 is closed.

4) Hydraulic system: (steel furnace shell)

The hydraulic station valve block adopts integrated block type, small volume, and the oil inlet and outlet paths are in one direction, which is convenient for installation of components and auxiliary piping.

  ( 2 ) All hydraulic components are joint venture manufacturers and domestic famous brand products.

  ( 3 ) The tilting of the furnace body is accomplished by two synchronized plunger cylinders.

( 4 ) The hydraulic device is used to power the tilting cylinder, the furnace rotating oil cylinder and the furnace lining out cylinder, and adopts the double pump and double electric form, and the hydraulic medium is hydraulic oil.

( 5 ) The hydraulic operating table is used to control the tilting and falling of the furnace body, the ejection of the lining, and the rotation of the furnace cover. The operation is realized by the manipulation handle. When the handle is not operated, the entire system can be automatically unloaded even if the pump is in operation. It avoids the defects of oil temperature rise caused by operation errors, high reliability, stable operation and no impact. Rexroth elements are used for hydraulic components.

5) Water-cooled cable:

The joint of the water-cooled cable is crimped by a cold pressing process and the copper strand is crimped. The outer sleeve of the water-cooled cable is made of a special flame-retardant rubber tube, and can withstand 0.5Mp a water pressure without leakage and cracking.

6) Change the furnace switch ( optional equipment ) :

The furnace change switch is used to switch the furnace body. Use a double tie switch and use the motor to drive the device. When the furnace is changed, there is a manual control button on the control panel to control the specified furnace position of the furnace to complete the furnace change operation. When the segment is powered, it stays in the original locked position and waits for the next furnace operation command. The control circuit of the furnace change switch has mutual protection function to ensure that the two furnace bodies are not connected to the intermediate frequency solid power supply at the same time.

VII) Cooling water system (optional):

1 . Plate heat exchanger

The mechanism of the plate heat exchanger is relatively simple . It consists of a stainless steel plate , a sealing gasket, a fixed pressing plate, a movable pressing plate, a compression bolt guide nut, an upper and lower guide rod and a column.

Stainless steel plate for a plate heat exchanger heat transfer element, two kinds of hot and cold fluid, respectively, at both sides of the plate countercurrent flow of heat from the hot fluid to the cold fluid to pass through the plate, the plate thickness of 0.6-0.8mmis not selected The rust plate, the thinner the plate, does not affect the bearing capacity, the better the heat exchange efficiency. The plate suppresses the adult-shaped corrugation, so that the fluid forms a turbulent flow when flowing, which increases the heat transfer efficiency and effectively prevents the formation of dirt.

　 The plate heat exchanger is compact in structure, and it is only necessary to loosen the bolts to move the movable clamping plate backwards during maintenance, unlike the shell-and-tube heat exchanger, which requires a large maintenance space. Moreover, the thickness of the heat exchanger plate selected by the plate heat exchanger is only 0.6mm~0.8mm , and the shell-and-tube heat exchanger casing is much heavier; therefore, the plate heat exchanger occupies the ground when the same heat exchange task is completed. Small size and light weight

2. Fully enclosed cooling tower

The furnace body and the power supply are respectively provided with two independent (also one set) fully enclosed cooling devices. The purpose of using two sets of cooling devices independent of each other is to avoid mutual influence. There is a water collecting tray under the cooling tower, and the spraying water is installed inside. The water inlet of the water collecting tray is equipped with a floating ball valve, which can automatically control the water level in the water collecting tray, and the water outlet has a spray water pump. Because the intermediate frequency power supply requires low temperature cooling water, the outlet water temperature should be controlled within 55 ° C. Since the temperature of the cooling water of the induction coil of the electric furnace is slightly higher, the thermal efficiency of the electric furnace can be improved, and the volume of the cooling device can be reduced, thereby reducing the cost. At the heart of the fully enclosed cooling unit is a spray-evaporated enclosed cooling tower. There are many heat-dissipating coils inside the cooling tower, and circulating water flows inside the coils without coming into contact with the air. The upper part of the cooling tower is equipped with a water spout and a cooling fan. During operation, the spray pump will pump the water to the upper spout, spray the water onto the outer surface of the coil, and the cooling fan will simultaneously draw air to vaporize the spray water and take away the heat of the circulating water in the coil. This advanced type of cooling unit has a high heat exchange efficiency.

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