Method for solving electromagnetic interference plasma cutting machine power supply

The power interference of CNC plasma cutting machine belongs to electromagnetic high frequency interference. From its working principle, the similar interference of NC plasma cutting machine itself can not be prevented. It can only be dealt with through the relevant prevention wrist and the anti-interference enhancement of the hardware of NC plasma cutting machine. The most direct harm of power interference of CNC plasma cutting machine lies in the interference to NC operating system. This is also the main reason why there was no similar problem in early manual cutting. Because there are electronic tubes and electronic components in the control system of NC plasma cutting machine, the corresponding anti-interference problem disposal means are also available. There are some differences, the following Wuhan Haichen Mechanical and Electrical Engineering Co., Ltd. will mainly on the anti-interference digital plasma cutting machine summary solutions:

1. The grounding system of CNC plasma cutting machine.

Attention should be paid to the grounding technology of NC plasma arc cutting system. Because the CNC part and servo unit make the moving part on the track, the disturbance intensity has a great relationship with the central connection of the system.

1. The separation of AC ground and DC ground prevents the interference introduced by AC power line from being transmitted to the control installation due to ground resistance, which not only ensures the safety of the internal devices installed in the control system, but also improves the reliability and stability of the system and reduces the ground current interference of the strong current equipment.

2. To float logically and separately from imitate float is to connect the control installation logically and imitatedly with the earth without conductor, and use the floating "ground" as the reference level of the system. This makes plasma arc and other external radiation interference and electrostatic interference can be suppressed at a very high level.

As the logical float significantly increases the interference induction of the analog circuit, a good approach is to connect the analog and logical separately to their respective bus bars, and then pass the bus bars of the analog ground through a capacitor grounding point at one point. For imitation, it forms a system of direct current and common ground.

3. The cabinet is well grounded.

CNC plasma arc cutting machine occupies a large area, it is better to lay alone the ground installation (connection open at least 3 meters); and grounding installation should be with the machine guide, cabinet and cable sliding support firmly connected. In this way, the induced high frequency interference voltage on the chassis has a leakage channel with low impedance, so that there is no possibility of the chassis voltage rising due to the accumulation of electric charge, which is safer for the personnel and is beneficial to suppressing the interference impact.

The main interference source of the CNC plasma cutting machine control system is the power supply part. It usually uses high-frequency arc starter to ignite the arc, high-frequency transformer secondary side voltage as high as 3000-6000V, pulse frequency of hundreds of kilohertz, radiation interference and pollution to the power grid (interference) are very strong; there are large current AC and DC contactors and various relay switching off on the grid will also form surge impact. Conventional plasma cutting machine arc together on the computer caused internal disorder, can not cut normally, the earliest CNC cutting machine and even request the user to arc and then start the computer, running CNC system program. This not only makes the operation cumbersome, the computer can not be fully used, but also has a serious impact on the life of the computer, so suppressing the interference of plasma power supply, reducing pollution to the power grid is the primary problem.

Two. Power supply of CNC plasma cutting machine

1. Increase shielding cover for high frequency arc igniter and reduce high frequency radiation.

2, transform the control circuit of plasma power supply.

The control power supply 220V of the original LG-200 plasma cutting machine is directly drawn from the grid voltage, and the starting/arc-extinguishing control line is directly drawn from the cutting machine to the numerical control cabinet. In the meantime, the power supply system of the numerical control CNC and the power supply system of the former LG-200 plasma cutting machine exceed the cable frame of tens of meters, so that the high frequency interference caused by the plasma/arc-extinguishing and the electromagnetic interference caused by the high current are directly Cascade into the power grid. The measure is to add an isolation transformer to the 220V high-voltage control line, and at the same time the starting/quenching control signal is isolated by relays into a relatively weak AC 24V control line to enter the numerical control cabinet. The problem is handled by the pan - 200 s.

3, other anti-interference measures

RC absorption circuit and varistor are added to the primary and secondary sides of the main transformer. Resistance and capacitance circuits are connected in parallel at the two ends of the current contactor and relay coil. High frequency bypass capacitance is locally installed in the DC. All these measures are aimed at suppressing interference sources and reducing the pollution to the grid voltage.