Energy-saving technology analysis of 1.5 ton steel shell melting furnace with inverter thyristor series

  Thyristor inverter series consisting of 1.5 tons of steel furnace shell

1. 1.5 tons of steel shell melting furnace single set of equipment:

1. Medium frequency melting furnace rectifier cabinet (series)

2. Supporting compensation capacitor cabinet (dedicated)

3. Melting furnace body (1.5 tons steel shell)

4, hydraulic system

5, the console, one

6. Connecting copper bars between the rectifier cabinet and the inverter cabinet

7, water-cooled cable four

8, model one

9, water dispenser

10, leaking furnace alarm device

11. The water connection part between the power supply and the furnace body

12, electrical control box

13, temperature automatic control system

Second, 1.5 tons of steel shell melting furnace applicable standards

1. GB10067.3-88 "Basic technical conditions of electric heating equipment. Induction electric heating equipment"

2, GB/T10066-88 "Testing methods for electric heating equipment - coreless induction furnace"

3, GB5959.3-88 "Safety of electric heating equipment - special requirements for induction and conductive heating equipment and induction melting equipment"

4. JB4086-85 "Technical Conditions for Electronic Control Equipment for Medium Frequency Induction Heating"

5, JB/T4280-93 "Intermediate frequency coreless induction furnace"

6. ZBK46001-87 "Semiconductor Frequency Conversion Device for Induction Heating"

7, GB/T14549-93 "Power Quality · Utility Grid Harmonics"

Third, 1.5 tons of steel shell melting furnace operating conditions

1, no more than 1500 meters above sea level.

2 , the ambient temperature is not higher than +40 ° C and not less than +5 ° C, good ventilation.

3, during use of the apparatus is stopped, without cooling water is not lower than the ambient temperature -30 ℃.

4, the surrounding medium relative humidity less than 85%.

5 , the power supply has sufficient capacity, the power frequency is 50Hz; the voltage fluctuation is not more than ± 5% and the waveform singularity is not more than ± 10%.

6, in the absence of a conductive, flammable, explosive dust, no corrosion of the metal and damage the insulation gas and vapor occasions.

7, used in the absence of a strong vibration and shock interior.

8 The inlet water temperature of the open cooling water is between +5 °C and +35 °C, and the device should not be used in the case of condensation. The water pressure is maintained at 1.5-3 kg/cm2. The water quality meets the requirements of industrial softened water.

Fourth, 1.5 tons of steel shell melting technical parameters

1, transformer parameters

2, IF power supply technical parameters

3, induction furnace body

4, hydraulic system parameters

5, power cooling water system parameters

6, furnace cooling water system parameters

7, comprehensive system parameters

Five, 1.5 tons of steel shell melting furnace introduction

5.1 The transformer used

Each set of inverter thyristor series 1.5 ton steel shell melting furnace must have a rectifier transformer with a capacity of 1250KVA for powering it. The transformer is oil-immersed and self-cooling, three-phase input and six-phase output, and the high-pressure side is equipped with a +5%, 0, -5% three-speed manual pressure regulating gear.

To adjust its output voltage. Such rectifier transformers generally adopt Y/d11, Y0 connection group mode, and the secondary output is two groups, one set of outputs is Y-type connection, and the other set of outputs is d11 type connection, so the phase of the two sets of outputs will be The difference between each other is 30°, that is, a rectification method of 12 pulses is formed. Compared with the six-pulse rectification, this rectification method can effectively suppress the 5th and 7th harmonics, and only a small number of 11th and 13th harmonics can effectively reduce the interference of harmonic components on the grid.

The transformer is equipped with a gas relay and an oil temperature gauge, which can be interlocked with the high-voltage switchgear. When the transformer is heavy or the oil temperature is too high, the high-voltage power supply is cut off to protect the transformer.

5.2 Analysis of intermediate frequency power supply used in inverter thyristor series 1.5 ton steel shell melting furnace

Design and manufacture of SCR series line IF power supply, its performance and reliability can be comparable with similar foreign products. The details are as follows:

5.2.1 Performance

1: The rectifier bridge of the SCR series power supply adopts full turn-on rectification. During the rectification process, the thyristor is always fully open, so the SCR series power supply has the following advantages.

a: The power factor is high. Regardless of the furnace condition, whether full power, half power or low power, the overall power factor of the equipment is always ≥ 0.95. Therefore, in terms of power supply and electricity, there are not only fines due to low power factor, but even rewards due to high power factor.

b: The number of KVA required for the transformer configured by the device is small. This means that transformers of the same capacity can be equipped with higher power furnaces, which increases transformer utilization.

c: The high-power power supply adopts 12-pulse rectification, which produces smaller harmonic components and has less impact on the power grid.

2: The rectifier bridge of the SCR series power supply is started by soft start, so there is no impact on the power grid when the power is turned on.

3: The inverter bridge of the SCR series power supply adopts a voltage feedback type series resonance circuit, so the SCR series power supply also has the following advantages.

a: High conversion efficiency. The conversion efficiency of converting electrical energy from three-phase power frequency alternating current to single-phase medium frequency alternating current is as high as 96%.

b: high melting rate. The SCR series power supply we produce can operate at constant power. No matter what kind of working state the furnace is in, it is oven, heat preservation or melting, and the power supply can adjust the running power at will.

c: High startup success rate. In any furnace condition, the startup success rate is 100%.

4: All main circuits of SCR series power supply adopt large-section copper bars, and the power loss is only 20% of water-cooled copper pipes.

5: SCR series power supply operates with low noise.

6: Perfect and appropriate protection.

a: Incoming current overcurrent protection. When the operating current of the device is greater than this value, the power supply stops and enters the protection state.

b: Incoming current limit, the line current of the limiting device operates below this value.

c: Capacitor voltage limit, the capacitor voltage of the limiting device operates below this value.

d: The electric furnace voltage is limited, and the electric furnace voltage limit of the limiting device is operated below this value.

e: The electric furnace current limit, the electric furnace current limit of the limiting device operates below this value.

f: Cooling water temperature protection. When the cooling water temperature is high, the power supply is protected.

g: Cooling water pressure protection. When the cooling water pressure is low, the power supply is protected.

7.2.2 Reliability aspects

1: Inverter trigger signal fiber transmission.

2: Control circuit board miniaturization.

3: Control hub core integration.

5.2.3 Convenience of maintenance.

Considering the convenience of the user for maintenance, such as the installation of the thyristor, our thyristor uses a frame mount, and the thyristor is installed vertically, so that if the thyristor needs to be replaced, one can Easy to replace without the need for another person to help.

5.3 furnace body introduction

Inverter thyristor series 1.5 ton steel shell melting furnace part includes electric furnace body, water-cooled cable, refractory clay, furnace lining quick-release device, main circuit copper platoon.

5.3.1 Furnace body

The furnace body is composed of an induction coil, a yoke, a hob, a tilting cylinder (a holding furnace and a furnace cover).

5.3.1.1 Induction coil

The induction coil is made of T2 cold-rolled rectangular copper tube of not less than 5mm. The induction coil is coated with mica tape and immersed insulating varnish. The exterior is coated with a layer of gray insulating varnish. The insulation layer has a withstand voltage greater than 5000V.

The induction coil is fixed by a series of bolts and insulating stays welded to its outer circumference. Coil solid

After the setting, the pitch error is not more than 2mm.

A stainless steel water cooling ring is arranged on the upper part and the lower part of the induction coil, and the purpose is to make the lining material uniformly heated in the axial direction and prolong the service life of the lining.

At the water outlet of the induction coil, several water temperature probes are installed according to the water path. When the water temperature of a certain road is blocked, the alarm can be immediately issued, and the intermediate frequency power supply can be automatically stopped.

5.3.1.2 yoke

The yoke is made of a high permeability cold rolled silicon steel sheet. The thickness of the silicon steel sheet is 0.3 mm. The yoke adopts a profiling structure, and the arc of the inner arc surface is the same as the outer arc of the induction coil, so that the yoke can be evenly distributed on the outer side of the induction coil, thereby maximally restraining the magnetic field radiated outward from the coil and reducing the external magnetic circuit. Magnetoresistance.

The yoke is clamped by stainless steel plates and stainless steel clamps on both sides and fixed by welding. A cooling water pipe is welded to the stainless steel plate on both sides for cooling the yoke. The cooling water pipe can withstand 0.45Mpa water pressure and no leakage within 15min.

After the yoke is assembled, the bending degree is not more than 4 mm, and the deviation between the theoretical center line and the actual center line is not more than 3 mm.

A PTFE sheet and an asbestos rubber sheet are interposed between the yoke and the coil. The PTFE sheet has high dielectric strength and high temperature resistance, and the asbestos rubber sheet has high heat resistance.This ensures insulation and heat resistance between the yoke and the coil. Each yoke is fixed by a screw rod fixed on the furnace shell, and a uniform top force is formed in one circumference of the coil, so that the yoke is fixed and the coil is fixed, and the coil is not generated during the melting and discharging process. mobile.

5.3.1.3 hob

The hob is divided into two parts.

5.3.1.3.1 Activity hob

The movable hob is used to mount the induction coil and the yoke. It is welded from profiled steel and steel plate and has a frame structure for easy maintenance. The operating platform at the top of the movable hob is made of thick steel plate to improve the strength and load-bearing capacity of the hob.

5.3.1.3.2 Fixed hob

The fixed hob is mounted on the foundation for carrying the movable hob. The upper part of the fixed hob is connected by the tilting shaft and the movable hob. Under the pushing of the tilting cylinder, the movable hob can be tilted forward by 95 degrees.

The hob section is designed with a large safety factor. Ensure that the hob has sufficient rigidity to run smoothly when carrying the maximum load.

5.3.1.4 Water-cooled cable

The connector of the water-cooled cable has a detachable structure and can be easily disassembled. The inside is connected to the copper strand by soldering. In this way, the connection is firm and the contact resistance is small.

The outer casing of the water-cooled cable is a rubber tube. This hose is not easy to burn and has good strength. It can withstand 0.45Mpa water pressure without leaking or breaking.

The rubber tube will age after long-term use and will be replaced at this time. This detachable structure does not need to damage the internal copper strands, and it is only necessary to disassemble the bolts on the joints to easily replace the outer rubber hoses.

The inside of the joint is sealed with a tapered cone and is electrically conductive. When the joint bolt is tightened, it naturally acts as both conductive and sealed.

5.3.1.4 refractory clay

Refractory clay is a highly insulating and insulating material that is applied to the inside and outside of the induction coil and has the following effects:

(1) Make the induction coil as a whole, reducing vibration and noise during operation.

(2) Protect the induction coil when the charge leaks.

(3) Conducive to the launch of the lining.

5.3.1.5 lining quick release device

The lining quick-release device is used to quickly remove the old lining. It includes a push block, a push cylinder and an operating mechanism.

The jacking block is mounted under the lining and is connected to the jacking cylinder through a pushing hole at the bottom of the furnace body. When the old furnace lining needs to be introduced, the electric furnace is tilted to 90 degrees, and the thrust pin is fixed by the fixing pin and the connecting flange at the bottom of the furnace body, and the old furnace lining can be pushed out by operating the manual valve to pressurize the oil cylinder.

Six , 1.5 tons of steel shell melting furnace main raw material manufacturers