心静电磁

　　induction coilAfter work, alternating current passes throughinduction coilDeformed magnetic field, according to Faraday's law of electromagnetic induction, alternating magnetic force cuts off the metal inside the coil to form an induced current. Since the metal itself has resistance to heat, the current in the process of flowing inside the metal generates heat, metal heating or melting. This is the basic principle of induction heating and induction melting. Then, let's learn how to solve the common ignition problems of medium and high frequency induction coils!

The operation of the induction coil has the following characteristics.

1. High voltage and high current flow through the coil;

2. The coil itself is in a high temperature working environment

3. Good insulation performance must be ensured between the coil and the coil. Ignition, the formation of a short circuit, will greatly reduce the efficiency of the electric furnace.

Since the coil itself is a conductor, the induction coil can not form a channel between the turns, so the insulation of the induction coil is very important, which directly affects the efficiency of the induction furnace and the safety of the working environment of the operators. But, unfortunately,induction coilThe insulation in the industry has not received enough attention, many manufacturers just after the completion of the coil, the surface of the ordinary insulation coating as a means of insulation. Most of these insulating coatings are organic substances, which have good insulation ability at room temperature, but with the rise of temperature, the performance of this kind of insulating coating deteriorates rapidly, and it gradually carbonizes itself. When the temperature exceeds 100C, it is completely carbonized and blackened, and completely loses its insulation ability.

The main reason for the insulation damage on the surface of the induction coil is that the working environment of the induction furnace is bad. Although there is a water cooling system, it cannot guarantee that the insulating coating always works in a low temperature environment. This is mainly due to the following reasons.

1. The induced current through the coil has a skin effect. In other words, the current is mainly concentrated on the surface of the copper tube, and the higher the frequency of the induced current, the higher the surface current density. Therefore, the heat of the induction coil copper pipe is concentrated on the surface, and the surface temperature in contact with the insulating paint is much higher than the temperature of the part in contact with the cooling water in the copper pipe. Even under the usual circulating water cooling conditions, the outlet water temperature is controlled at 50-60, and the temperature of the copper pipe surface exceeds 80.

2. Conductive heat of molten steel in the furnace. The new furnace lining is very thick, which can effectively prevent the heat of molten steel in the furnace from being transferred to the surface of the coil. However, with the rapid erosion of the furnace lining in the later period, the heat of the molten steel transferred to the surface of the coil is much higher than that of the new furnace lining. When the surface is actually measured, the temperature of the coil lining layer is about 80 when the new product is new (the thickness of the lining layer is about 15cm). When the temperature of the coil lining layer reaches about 200 after the lining layer is later (the thickness is about 5cm ), the temperature of the coil lining layer rises to nearly, and the usual insulating coating layer is used at this time.

3. The cooling capacity of cooling water decreases, mainly due to the impact of water quality. The cooling water is prone to fouling at high temperatures. Especially in the northern and western regions where the water quality is hard, the scaling of cooling water is obvious, the copper pipe is blocked, the water pressure of the water flow is reduced, the cooling capacity is obviously decreased, and the temperature rise accelerates the scaling. If this happens, the temperature of the copper pipe surface will rise rapidly, and ordinary insulating coatings will be carbonized and destroyed in a short time. If the insulating coating on the surface of the coil is destroyed and the insulating ability is lost, the coil will easily catch fire. The main reasons are as follows.

1. The cause of water vapor, especially after the new lining is started, the moisture in the lining material is suddenly heated and gasified, exudes through the small holes of the coil slurry, and condenses into water droplets soon after encountering the coil with lower temperature. Water is a conductor and will soon catch fire.

2. The walking drip of copper pipe. Because the circulating water in the copper pipe may drip locally.

3. Metal dust on the operation site accumulates on the surface of the coil, causing short circuit and fire.

Once a fire occurs, the temperature rises rapidly. First, destroy the remaining insulating coating of the part, attract the arc, destroy the copper tube, and accelerate the fire until serious production accidents and property losses.

The above introduction is how to solve the common ignition problem of medium and high frequency induction coils. The overload action of the electric furnace is also one of the important reasons that cause the coil to catch fire. After the operation exceeds the rated power, the current and voltage passing through the coil increase, and the calorific value of the coil increases. Therefore, the insulating layer is destroyed at high temperature, and the insulating ability is easily lost, and the fire under high voltage is easy to occur.