Electrical bonding is a process in which parts of an electrical circuit assembly or sub-modules within a system are connected electrically by their joints or by any low-resistance bonding media (Jumpers).
Electrical bonding is simply the joining of two conductors together, that may be two wires, a wire, and a pipe, or two pieces of equipment. Electrical bonding ensures that these two conductors that are bonded together will be at the same electrical potential. That means no current flow will take place between two bonded bodies because they have some potential.
What is Electrical Bonding?
Electrical bonding is a process of connecting metallic objects that may be exposed to electrical faults or induced voltages to the grounding conductors. This ensures that in the events of fault the current will have a low resistance path to take to trip the over-current devices as quickly as possible, as well as providing a path for static electricity and induced voltage to drain out.
The main purpose of electrical bonding is to make a homogeneous structure with respect to the flow of radio frequency (RF) current so that it would experience the minimum barrier as it crosses one surface to the other without developing electrical potential at the crossover point. Bonding to electrical earth is used extensively to ensure that all conductors (Person, surface, and product) are at the same electrical potential. When all the conductors are at the same potential then no discharge will occur.
Electrical bonding requirements
In order to ensure electromagnetic compatibility (EMC) specification the various components of a module or all the modules of the system are connected to a common chassis or common reference ground via low impedance electrical path that should provide non-zero impedance at all frequencies. This kind of bonding provided to meat EMC specifications are known as EMC Bond and the process is known as EMC Bonding.
[ ##eye## Notch filter- Theory, circuit design, and Application]
This is specially important in the areas where the occupant will be able to come in direct contact with the metal parts or areas where there is a potential for explosive gas or ducts to exit.
Good bonding is required for mounting line-filter modules on the chassis that serves as a drain for EMI currents, or for connector shells to equipment enclosures to ensure shielding integrity of cable shields that are terminated on these connectors, or for ensuring shielding integrity over seams and joints to avoid leakage of RF energy.
The main purpose of electrical bonding is to prevent voltage difference between two parts being joined.
Why Electrical bonding is important?
Whenever voltage is applied to the conductor, it can be a wire or anything in its metallic body, there will be some residual voltage drop across the length of the conductor based on its size, material, and length.
There is some resistance even in highly conductive copper and aluminum. Then due to this resistance based on the distance from the nearest grounding connection, a small potential difference can occur.
If there is a difference between a cable tray and a nearby staircase, then someone who touches both the metal objects at once might experience an electrical shock.
[ ##eye## Meaning of 1 unit electricity]
A more frequent electrical bonding connection will reduce the potential between metallic objects and it decreases the chances of unintentional electrical shock from static or induced voltages.
Residential swimming pools can also be susceptible to touch potential differences, especially when water meats metal surfaces. Metal parts of pools, hot tubes, and fountains must be bonded to earth to reduce the risk of electrical shock to anyone who might come in contact with these surfaces, especially when the humid environment increases the chances of providing a path to the ground through a person’s body.
Types of Electrical bonding
To accomplish this kind of low resistances, a bond between these two metal walls, a hole can be drilled in the adjoining parallel walls and the two cabinets can be bolted together with the star washers at the point of contact between the walls.
[ ##eye## Fundamentals of Electrical Energy]
Electrical bond involves dissimilar metals where non-linear junctions can develop at the bond, leading to the generation of harmonics, especially under the strong RF fields that causing interference.
To reduce the above problem a radical approach is required if the bond is to work at high frequencies. The most effective method is to divide the bonding process into two categories as Mechanical bonding and Electrical bonding.
Electrical bonding are classified into two types as:
- Direct bonding
- Indirect bonding
1. Direct Bonding
Whereas semi-permanent bonding is carried out by using bolted connections. For a satisfactory result of direct bonding, bolt/screw will serve as faster and pressure of about 90 to 100 Kg/Cm2 needed to be maintained.
2. Indirect Bonding
Here in this type of electrical bonding, other than the primary bond with the help of mechanical joint, indirect bonding is being employed with the help of straps or jumper wires.
These jumpers exhibit self-inductance and residual capacitance in the electrical circuits at high frequencies due to skin effect phenomena.
In such a case, a sheet-metal strap (called bond strap) or special flat braids are used. For the sheet-metal strap to work effectively, its width to thickness ratio should be maintained at 10 or more, while the length to width ratio should not exceed 5.
Electrical bonding of Earth wire
[ ##eye## Surge impedance loading (SIL) of Transmission line]
If the bonding is likely to be exposed to moisture or a corrosive environment, a coating of paint or grease is applied over the bond to make it free from corrosion.
Electrical bonding behavior at RF
This circuit acts as a parallel resonance circuit. So the circuit provides very high impedance at higher frequencies.
Due to the skin effect at a higher frequency, there becomes a flow of current via the outer surface of the conductor. Hence due to this, the bond offers very high resistance in the circuit.
very good....
ReplyDelete