German imported PEKUTECH sealing strip 2701

German imported PEKUTECH sealing strip 2701

German imported PEKUTECH sealing strip 2701

Jiangsu Qiucheng Electromechanical Co., Ltd

Professional procurement of European industrial control products and spare parts.

Advantages of Supply Brands and Models: Wurth Hardware Tools and Chemicals, Hahn Cooper, Gaimi Valves, Schmeisser Switches, IMM Nozzles, Ergowiss Hydraulic Lift Systems, Socla Valves, Kobold Flow Meter Switches, SBS Balancing Devices, ODU Connectors, SCHURTER Filters, AMF Fixtures, Phoenix Wig Miller Terminal Connectors, Bentley Envision Module Cards, etc

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The working principle of a DC generator is to convert the alternating electromotive force induced in the armature coil into a DC electromotive force when it is led out from the brush end by the commutator in conjunction with the commutation effect of the electric brush.

The direction of induced electromotive force is determined according to the right-hand rule (the magnetic induction line points towards the palm of the hand, the thumb points towards the direction of the conductor's movement, and the other four fingers point towards the direction of induced electromotive force in the conductor).

Working principle of DC motor

The direction of force acting on a conductor is determined by the left-hand rule. This pair of electromagnetic forces forms a torque acting on the armature, which is called electromagnetic torque in a rotating motor. The direction of the torque is counterclockwise, attempting to make the armature rotate counterclockwise. If this electromagnetic torque can overcome the resistance torque on the armature (such as the resistance torque caused by friction and other load torques), the armature can rotate counterclockwise.

DC motor is an electric motor that operates on DC working voltage and is widely used in recorders, video recorders, DVD players, electric shavers, hair dryers, electronic watches, toys, etc.

Electromagnetic editing and broadcasting

An electromagnetic DC motor consists of stator magnetic poles, rotor (armature), commutator (commonly known as commutator), brushes, casing, bearings, etc,

The stator magnetic pole (main magnetic pole) of an electromagnetic DC motor is composed of an iron core and an excitation winding. According to the different excitation methods (formerly known as excitation), it can be divided into series excited DC motors, parallel excited DC motors, separately excited DC motors, and compound excited DC motors. Due to different excitation methods, the law of stator magnetic flux (generated by the excitation coil of the stator magnetic pole after being energized) is also different.

The excitation winding and rotor winding of a series excited DC motor are connected in series through electric brushes and commutators. The excitation current is proportional to the armature current, and the magnetic flux of the stator increases with the increase of excitation current. The torque is approximately proportional to the square of the armature current, and the speed rapidly decreases with the increase of torque or current. Its starting torque can reach more than 5 times the rated torque, and the short-term overload torque can reach more than 4 times the rated torque. The speed change rate is large, and the no-load speed is very high (generally not allowed to operate under no-load). Speed regulation can be achieved by connecting external resistors in series (or parallel) with the series excitation winding, or by swapping the series excitation winding in parallel.

The excitation winding of a parallel excited DC motor is connected in parallel with the rotor winding, and its excitation current is relatively constant. The starting torque is proportional to the armature current, and the starting current is about 2.5 times the rated current. The speed slightly decreases with the increase of current and torque, and the short-term overload torque is 1.5 times the rated torque. The rate of change in rotational speed is relatively small, ranging from 5% to 15%. Speed can be adjusted by weakening the constant power of the magnetic field.

The excitation winding of the DC motor is connected to an independent excitation power supply for power supply,

Its excitation current is also relatively constant, and the starting torque is proportional to the armature current. The speed variation is also between 5% and 15%. The speed can be increased by weakening the magnetic field constant power or reduced by lowering the voltage of the rotor winding.

In addition to parallel excitation windings, the stator poles of a compound excited DC motor are also equipped with series excitation windings (with fewer turns) connected in series with the rotor winding. The direction of magnetic flux generated by the series winding is the same as that of the main winding. The starting torque is about 4 times the rated torque, and the short-term overload torque is about 3.5 times the rated torque. The speed change rate is 25%~30% (related to the series winding). The speed can be adjusted by weakening the magnetic field strength.

The commutator segments are made of alloy materials such as silver copper and cadmium copper, and are molded from high-strength plastic. The electric brush slides in contact with the commutator, providing armature current to the rotor winding. The brushes of electromagnetic DC motors generally use metal graphite brushes or electrochemical graphite brushes. The iron core of the rotor is made of stacked silicon steel sheets, usually 12 slots, embedded with 12 sets of armature windings, connected in series between each winding, and then connected to 12 commutator segments separately.

Jiangsu Qiucheng Electromechanical Co., Ltd. is a modern enterprise that integrates research and development, engineering, sales, and technical services. It is a competitive equipment supplier in the field of automation in China. The company mainly deals in industrial automation products such as mechatronics equipment, high-precision analytical and testing instruments, environmental and new energy industrial equipment, and electric tools from developed countries such as Europe, America, Japan, and South Korea.

Principle - Under inert gas protection, the welding method uses the arc heat generated between the tungsten electrode and the workpiece to melt the base metal and filler wire (or no filler wire is required), forming a weld seam. The electrode does not melt during the welding process.

Main characteristics - strong adaptability (stable arc, no splashing); Low welding productivity (poor current carrying capacity of tungsten electrode (preventing melting and evaporation of tungsten electrode, preventing tungsten inclusion in weld seam); The production cost is relatively high.

Application - Almost all metal materials can be welded, commonly used for welding stainless steel, high-temperature alloys, aluminum, magnesium, titanium and their alloys, refractory active metals (zirconium, tantalum, molybdenum, niobium, etc.), and heterometallic metals. Welding parts with a thickness generally below 6 millimeters, or bottom welding for thick parts. The narrow gap TIG automatic welding with a thickness of over 90mm can be achieved using small angle groove (narrow groove technology).

6. Plasma arc welding

Principle - The method of using a water-cooled nozzle to restrain the arc and obtain a high-energy density plasma arc for welding.

Main features (compared to argon arc welding) - ⑴ Energy concentration, high temperature, small hole effect can be obtained for most metals within a certain thickness range, which can achieve full penetration and uniform reverse forming of the weld seam. ⑵ The arc stiffness is good, and the plasma arc is basically cylindrical. The change in arc length has a relatively small impact on the heating area and current density on the weldment. So, the effect of arc length variation in plasma arc welding on weld formation is not significant. Welding speed is faster than argon arc welding. Capable of welding finer and thinner workpieces. The equipment is complex and the cost is high.

application

⑴ Penetrating (small hole) plasma arc welding: Using the characteristics of small plasma arc diameter, high temperature, high energy density, and strong penetration force, under appropriate process parameters (large welding current of 100A~500A), the welded part is melted through, and under the action of plasma flow force, a small hole is formed to penetrate the welded part, and a part of the plasma arc is sprayed from the back of the welded part in the plasma arc welding method. Can be welded on one side and formed on both sides, welding 3-8mm stainless steel, 12mm titanium alloy, 2-6mm low carbon steel or low alloy structural steel, as well as butt welding of copper, brass, nickel and nickel alloys. (The plate is too thick, limited by the energy density of the plasma arc, making it difficult to form small holes; the plate is too thin, and the small holes cannot be sealed by liquid metal, making it impossible to achieve small hole welding.)

⑵ Fusion type (immersion type) plasma arc welding: using a smaller welding current (30A~100A) and a lower plasma gas flow rate, using a hybrid plasma arc welding method. No small hole effect is formed. Mainly used for welding thin plates (0.5-2.5 millimeters or less), welding of multiple layers after sealing the bottom weld, and welding of fillet welds.

⑶ Microbeam plasma arc: plasma arc welding with welding current below 30A. The nozzle diameter is very small (Φ 0.5~Φ 1.5 millimeters), resulting in needle shaped and fine plasma arcs. Mainly used for welding ultra-thin, ultra small, and precision welded parts below 1 millimeter.

Note

1. The above are several commonly used fusion welding methods, each with its own advantages and disadvantages. When choosing a welding method, there are many factors to consider, such as the type of welding material, plate thickness, and the position of the weld in space. The principle of selecting welding methods is to use welding methods with lower total costs while ensuring the quality of the welded joints.

Welding temperature control

The temperature of the molten pool directly affects the welding quality. High molten pool temperature, large molten pool, and good fluidity of the molten iron make it easy to fuse. However, when it is too high, the molten iron is prone to flow down, and the back of single-sided welding and double-sided forming is easy to burn through, forming weld beads and difficult to control forming. In addition, the plasticity of the joint decreases, and bending is prone to cracking. When the temperature of the molten pool is low, the molten pool is small, the molten iron is dark, the fluidity is poor, and defects such as incomplete penetration, incomplete fusion, and slag inclusion are prone to occur.

The temperature of the molten pool is closely related to welding current, electrode diameter, electrode angle, arc combustion time, etc. The following measures are taken to control the molten pool temperature based on relevant factors.

diameter

1. Welding current and electrode diameter: welding is selected based on the spatial position and welding level of the weld seam

When starting welding, the selected welding current and electrode diameter are larger, and the vertical and horizontal positions are smaller. For the bottom layer of the 12mm flat butt welding, a welding rod with a diameter of 3.2mm and a welding current of 80-85A is used. For the filling and cover layer, a welding rod with a diameter of 4.0mm and a welding current of 165-175A are used. Reasonable selection of welding current and electrode diameter is easy to control the temperature of the molten pool and is the basis for weld formation.

method

2. The method of strip transportation involves using a circular strip transportation with a molten pool temperature higher than that of a crescent shaped strip transportation, which in turn is higher than the molten pool temperature of a serrated strip transportation. In the 12mm flat welding bottom layer, a serrated strip transportation is used, and the amplitude of the swing and the pause on both sides of the groove are used to effectively control the molten pool temperature, making the size of the molten hole basically the same. The probability of no weld bead or burn through at the root of the groove is reduced, and incomplete welding is improved, making single-sided welding and double-sided forming of the flat welding of the plate no longer a difficult point.

angle

3. When the angle between the welding rod and the welding direction is 90 degrees, the arc is concentrated, the temperature of the molten pool is high, the angle is small, the arc is dispersed, and the temperature of the molten pool is low. For example, for a 12mm flat welding bottom layer, the angle of the welding rod is 50-70 degrees, which reduces the temperature of the molten pool and avoids the formation of weld beads or elevations on the back. For example, after changing the welding rod for the bottom layer of the 12mm board vertical welding seal, a welding rod angle of 90-95 degrees is used for the joint to rapidly increase the temperature of the molten pool, enable the molten hole to open smoothly, and form a relatively flat back, effectively controlling the phenomenon of concave joint points.

time

4. In the internship teaching of horizontal and vertical fixed welding of a φ 57 × 3.5 pipe, the arc breaking method is used for welding. When welding the bottom layer, the frequency of arc breaking and the arc burning time directly affect the temperature of the molten pool. Due to the thin wall of the pipe, the ability to withstand the heat of the arc is limited. If the arc breaking frequency is slowed down to reduce the temperature of the molten pool, it is easy to produce shrinkage holes. Therefore, the arc burning time can only be used to control the temperature of the molten pool. If the temperature of the molten pool is too high and the molten hole is large, the arc burning time can be reduced to lower the temperature of the molten pool. At this time, the molten hole becomes smaller, the internal forming height of the pipe is moderate, and the welding seam inside the pipe is avoided from being too high or producing weld beads.

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