Circuits with different types and functions of grounding wires have different grounding methods. Common grounding methods in electronic power equipment are as follows:
1. Safety grounding wire
The safety grounding wire connects the shell of the high-voltage equipment with the earth. The first is to prevent the accumulation of electric charges on the case and the generation of electrostatic discharges that endanger the equipment and personal safety. For example, the grounding of the computer case and the tail dragging on the ground of the tank truck are all to release the accumulated charges and prevent accidents. ; Second, when the insulation of the equipment is damaged and the casing is charged, the protection of the power supply is promoted to cut off the power supply to protect the safety of workers, such as the casing of refrigerators and rice cookers. The third is to shield the huge electric field of the equipment and play a protective role, such as the protective fence of civil transformers.
2. Lightning protection grounding wire
When power electronic equipment is struck by lightning, whether it is a direct lightning strike or an induced lightning strike, if there is no corresponding protection, the power electronic equipment will be greatly damaged or even scrapped. In order to prevent lightning strikes, we generally set up lightning rods at high places (such as roofs, tops of chimneys) to connect with the earth to prevent the safety of equipment and personnel from being jeopardized by lightning. Safety grounding wires and lightning protection grounding wires are used to provide safety protection measures for electronic and electric equipment or personnel to protect the safety of equipment and personnel.
3. Working ground wire
The working ground wire is a reference potential provided for the normal operation of the circuit. This reference potential is generally set to zero. The reference potential can be set to a certain point, a certain section or a certain block in the circuit system. When the reference potential is not connected to the ground, it is regarded as a relative zero potential. But this relative zero potential is unstable, it will change with the change of the external electromagnetic field, so that the parameters of the system will change, resulting in unstable operation of the circuit system. When the reference potential is connected to the earth, the reference potential is regarded as the zero potential of the earth, and will not change with changes in the external electromagnetic field. But unreasonable working grounding will increase the interference of the circuit. For example, the interference caused by the incorrect grounding point, the interference caused by the common terminal of the electronic equipment is not connected correctly. In order to effectively control the circuit to produce various interferences in the work, so that it can comply with the principle of electromagnetic compatibility. When we design the circuit, according to the nature of the circuit, the working ground can be divided into different types, such as DC ground, AC ground, digital ground, analog ground, signal ground, power ground, power ground, etc. Different grounds should be set separately. Don't mix them together in one circuit. For example, the digital ground and analog ground cannot share the same ground wire, otherwise the two circuits will produce very powerful interference and paralyze the circuit!
4. Signal wires
The signal ground is the common reference ground for the zero potential of various physical quantity signal sources. Since the signal is generally weak and susceptible to interference, unreasonable grounding will cause interference in the circuit, so the requirements for the signal ground wire are higher.
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