Control scheme of electric welding machine group dynamic compensation filter

Application field of spot welding machine

1. Welding of multilayer positive and negative electrodes of power battery, welding of nickel mesh and nickel plate of nickel metal hydride battery;
2. Electric welding of copper and nickel plates for lithium batteries and polymer lithium batteries, electric welding and welding of aluminum platinum and aluminum alloy plates, electric welding and welding of aluminum alloy plates and nickel plates;
3. Automobile wiring harness, wire end forming, welding wire welding, multi-wire welding into wire knot, copper wire and aluminum wire conversion;
4. Use well-known electronic components, contact points, RF connectors and terminals to weld cables and wires;
5. Roll welding of solar panels, flat solar heat absorbing reaction panels, aluminum-plastic composite pipes, and patchwork of copper and aluminum panels;
6. Welding of high-current contacts, contacts, and dissimilar metal sheets such as electromagnetic switches and non-fuse switches.
Suitable for instantaneous speed electric welding of rare metal materials such as copper, aluminum, tin, nickel, gold, silver, molybdenum, stainless steel, etc., with a total thickness of 2-4mm; widely used in car internal parts, electronic devices, household appliances, motors, refrigeration Equipment, hardware products, rechargeable batteries, solar power generation, transmission equipment, small toys and other manufacturing industries.
Working principle of load
Electric welding machine is actually a kind of transformer with the characteristics of reducing the external environment, which converts 220 volts and 380 volts of alternating current into low voltage direct current. Welding machines can generally be divided into two types according to the type of output switching power supply, one is alternating current; the other is direct current. The DC welding machine can also be said to be a high-power rectifier. When the positive and negative poles are inputting AC power, after the voltage is transformed by the transformer, it is rectified by the rectifier, and then the power supply with a descending external characteristic is output. When the output terminal is turned on and off, a large voltage change occurs, and an arc is ignited when the two poles are short-circuited instantaneously. Using the generated arc to melt the welding rod and welding material to achieve the purpose of cooling and combining welding transformers has its own characteristics. The external feature is that the working voltage drops sharply after the electric stage is ignited.



load application

Electric welders use electrical energy to instantly convert electrical energy into heat. Electricity is very common. The welding machine is suitable for working in a dry environment and does not require too many requirements. Electric welding machines are widely used in various fields because of their small size, simple operation, convenient use, fast speed, and strong welds. They are especially suitable for parts with high strength requirements. They can instantly and permanently join the same metallic material (or dissimilar metals, but with different welding methods). After heat treatment, the strength of the weld seam is the same as that of the base metal, and the seal is good. This solves the problem of sealing and strength for making containers for storing gases and liquids.
The resistance welding machine has the characteristics of high production efficiency, low cost, saving raw materials, and easy automation. Because of its coordination ability, conciseness, convenience, firmness and reliability, it is widely used in aerospace, shipbuilding, electric energy, electronic devices, automobiles, light industry and other industrial production industries, and is one of the key welding methods.

Load Harmonic Characteristics

In systems with large load changes, the amount of compensation required for reactive power compensation is variable. Rapid impact on loads, such as DC welding machines and extruders, absorbs reactive loads from the power grid, causing voltage fluctuations and flickers at the same time, reducing the effective output of motors, reducing product quality, and shortening the service life of equipment. Traditional fixed reactive power compensation cannot meet the requirements of this system. Our company is committed to the design of this control system, which can automatically track and real-time compensation according to load changes. The power factor of the system exceeds 0.9, and the system has discrete system loads. Harmonic currents caused by discrete system loads can be filtered while compensating for reactive loads.
During the process of using the welding machine, a certain electromagnetic field will be generated around the welding machine, and radiation will be generated to the surrounding area when the arc is ignited. There are light substances such as infrared light and ultraviolet light in electro-optic light, as well as other harmful substances such as metal vapor and dust. Therefore, adequate safeguards must be employed in the operating procedures. Welding is not suitable for welding high carbon steel. Due to the crystallization, shrinkage and oxidation of the welding metal, the welding performance of high-carbon steel is weak, and it is easy to crack after welding, resulting in hot cracks and cold cracks. Low-carbon steel has good welding performance, but it must be properly operated during the process. It is very troublesome in rust removal and cleaning. The weld bead may produce defects such as slag cracks and pore occlusal, but proper operation can reduce the occurrence of defects.

the problem we are facing

The application of welding equipment in the automobile manufacturing industry mainly has power quality problems: low power factor, large reactive power and voltage fluctuations, large harmonic current and voltage, and serious three-phase imbalance.
1. Voltage fluctuation and flicker
The voltage fluctuation and flicker in the power supply system are mainly caused by the user load fluctuation. Spot welders are typical fluctuating loads. The voltage change caused by it not only affects the welding quality and welding efficiency, but also affects and endangers other electrical equipment at the common coupling point.
2. Power factor
The large amount of reactive power produced by the spot welder’s work can lead to electricity bills and electricity fines. Reactive current affects transformer output, increases transformer and line loss, and increases transformer temperature rise.
3. Harmonic Harmonic
1. Increase the line loss, make the cable overheat, age the insulation, and reduce the rated capacity of the transformer.
2. Make the capacitor overload and generate heat, which will accelerate the deterioration and destruction of the capacitor.
3. The operation error or refusal of the protector causes the failure of the local switching power supply.
4. cause grid resonance.
5. Affect the efficiency and normal operation of the motor, generate vibration and noise, and shorten the life of the motor.
6. Damage sensitive equipment in the grid.
7. Make various detection instruments in the power system cause deviations.
8. Interfering with communication electronic equipment, causing control system malfunctions and malfunctions.
9. The zero-sequence pulse current causes the neutralization current to be too large, causing the neutralization to become hot and even fire accidents.
4. Negative sequence current
The negative sequence current causes the output of the synchronous motor to decrease, causing additional series resonance, resulting in uneven heating of all components of the stator and uneven heating of the surface of the rotor. The difference in three-phase voltage at the motor terminals will reduce the positive sequence component. When the mechanical output power of the motor remains constant, the stator current will increase and the phase voltage will be unbalanced, thereby reducing operating efficiency and causing the motor to overheat. For transformers, the negative sequence current will cause the three-phase voltage to be different, which will reduce the capacity utilization of the transformer, and will also cause additional energy damage to the transformer, resulting in additional heat generation in the magnetic circuit of the transformer coil. When the negative-sequence current passes through the power grid, although the negative-sequence current fails, it will cause output power loss, thereby reducing the transmission capacity of the power grid, and it is very easy to cause the relay protection device and High-frequency maintenance produces common faults, thereby improving the diversity of maintenance.

Solutions to choose from:

Option 1 Centralized processing (applicable to multiple intermediate frequency electric furnaces that share a transformer and run at the same time)
1. Adopt harmonic control three-phase co-compensation branch + phase-separated compensation adjustment branch. After the filter compensation device is put into operation, the harmonic control and reactive power compensation of the power supply system meet the requirements.
2. Adopt active filter (remove the order of dynamic harmonics) and passive filter bypass, and after supplying to the filter compensation device, require invalid compensation and harmonic countermeasures of the power supply system.
Option 2 In-situ treatment (applicable to the relatively large power of each welding machine, and the main harmonic source is in the welding machine)
1. The three-phase balance welding machine adopts harmonic control branch (3rd, 5th, 7th filter) joint compensation, automatic tracking, local harmonic resolution, and does not affect the operation of other equipment during the production process. The reactive power reaches the standard.
2. The three-phase unbalanced welding machine uses filter branches (3 times, 5 times and 7 times of filtering) to compensate respectively, and the harmonic reactive power reaches the standard after being put into operation.

Post time: Apr-13-2023