Plasma cutting machine schematic

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Photocoupler

Plasma cutting uses high-temperature, high-speed plasma arcs as thermal energy to melt the cut metal and blow away the molten metal with high-speed airflow. It can be used for various metal materials (stainless steel, carbon steel, alloy copper, aluminum, copper, Nickel, titanium, etc. are cut, which has the characteristics of fast cutting speed, narrow slit, small deformation and material saving.

Air plasma cutting machine is based on compressed air. It is prone to failure due to frequent work, frequent work place and poor environmental conditions. Here is an example of LGK8-63 cutting machine, analyzing its basic working principle and introducing some common ones. Fault repair processing, the schematic diagram is shown in the attached figure.

I. Working principle The air plasma cutting machine mainly includes: main circuit, control circuit and gas path. 1. The main circuit includes contactor KM, three-phase transformer B1, three-phase bridge rectifier (from D1~D6) , C1 ~ C6 composition), high-frequency oscillator (composed of B2, B4, FP, C12). 2, the control loop is composed of control transformer B3 and J1, J2, J3, D7, C11, R3 and other components. 3, gas The road part is composed of decompression and electromagnetic valve DF.

The principle is as follows: After connecting the power supply and the air source, close the switch K1. The power indicator XD is on, and the cooling fan FM rotates immediately. Press the torch micro switch K3, the relay J1 is energized and its normally open When the point is turned on, the solenoid valve DF is actuated, the gas path is turned on, and the torch is pre-ventilated.

The other normally open contact turns on the resistor R3, and the diode D7 charges the capacitor C11 to form a delay circuit. After 3 to 5 seconds, the relay is completed. The relay J2 is energized and closed, the contactor KM is electrically closed, and the main circuit is energized, and the transformer B1 is passed through the transformer B1. Rectifier bridge. The positive pole is directly connected to the workpiece through B5 through the connecting line, the negative pole is output through B2, and the main circuit is energized. At the same time, the auxiliary normally open contact of the contactor KM turns on the relay J3.DK as the normally closed contact, which makes the change B4 is powered. B4 primary voltage is 220V, taken from transformer B3 primary auto-coupling tap, B4 secondary voltage is about 2500V, output to high-voltage capacitor C12 (102M/10kV two parallel) transformer B2 (primary winding 3 匝. times The stage winding 10 匝 is in the working main circuit). The transformer B2 is inductively superimposed on the negative pole of the main circuit - the high voltage, the torch is close to the contact workpiece (positive electrode), and the arc is cut.

In the figure, FP is the protection discharge air gap, the spacing is adjustable, the normal is 1~12mm. When the arc cutting workpiece is cut, the arc current causes the reed switch DK contact action in the coil B5 (8匝) to be disconnected, and the relay J3 loses power. When the high voltage transformer B4 is cut off, the arc ignition circuit is stopped. When the cutting is completed and the torch micro switch K3 is released, the relay J1 is powered off and reset, the contactor KM main contact is disconnected, and the main circuit stops outputting.

Due to the charging and discharging action of C11 in the RC circuit, the relay J2 is delayed and reset, so that the gas path is delayed by 10 seconds, and the torch is effectively cooled to protect the whole cutting process: pre-venting one main circuit power supply - high voltage lead Arc-extinguishing arc-gas hysteresis-stop. Transformer B1 is Y/Y connection, the primary side line voltage is 380V, the secondary side line voltage is 170V, the rectified DC no-load voltage is 240V, and the output is 120V when there is a workload. .

Second, the defects of the plasma cutting machine

This type of plasma cutting machine analyzes the main circuit, control circuit, etc. from its schematic or actual structure. It does not use an integrated circuit. Although the structure is simple, there are some defects. Because the power supply line is connected to a terminal board on the machine, and then from the terminal. The board is directly connected to the contactor KM. On/off is only the on/off control loop switch K1, and then the contactor KM is controlled. In actual use, if the contactor KM core jam or contact sintering occurs (this fault is very common), this The cutting machine still has a voltage output. It is easy to cause the failure of the continuous power supply. From the perspective of the protection equipment and the staff or from the maintenance point of view, at least one capacity between the power supply line and the contactor KM needs to be about 30A (according to the equipment). Three-phase circuit breakers with capacity to estimate).

It is worth mentioning that the main circuit has been powered during the arc-triggering process, the main circuit has been powered, the control loop works, J3, B4 work, there is an arc voltage on the number of B2, superimposed on the main circuit. The voltage of the arc-inducing component; the capacitance C13 between the output lead wires of the workpiece, the capacitance of the line ground C14, C15 is coupled, and is added to the secondary of the transformer B1, and is fed back to the power supply side through the winding inter-turn capacitor C16, causing pollution to the power frequency power supply. Use a high internal resistance digital multimeter DC voltage 1000V block, one pen laps the power supply line into any phase, the other pen is suspended, the digital multimeter display value is an unstable value (well above 0V).