Shenhai Explosion-Proof
For enhanced-safety electrical systems, wiring connections can be categorized into external electrical connections (where external cables enter the enhanced-safety enclosure) and internal electrical connections (between components inside the enclosure). Both types of connections typically utilize copper-core cables due to their high mechanical strength, low resistance, and superior conductivity.
External Electrical Connections:
When making external connections, cables should enter the enhanced-safety enclosure through a cable gland. The connection between the cable core and the internal connectors (terminals) must ensure safe passage of the rated electrical current, with connector cross-sectional areas sized appropriately.
Internal Electrical Connections:
Internally, all wiring should be arranged and positioned to avoid high-temperature and moving parts. If the wires are long, they must be secured at suitable points. Additionally, internal connections should not include intermediate joints.
In operation, all connections between wires and terminals (like conductive bolts) must be secure and free from looseness, preventing disconnection. Various methods can be employed to achieve this:
1. Bolt-Nut Compression Connection:
For bolt-nut compression, the wire core should be tightly secured by a lug (an “O” ring terminal, not a “0” ring) on the terminal, using a nut. Cold-press connections are preferred for the wire core and lug. Alternatively, the wire core can be knotted, tinned, and flattened for a similar effect.
In bolt-nut compression, it’s essential that conductive bolts (terminals) are made of copper, especially under high current. Similarly, copper washers should be used, and anti-loosening measures like steel nuts compressing the copper nuts or equivalent should be in place. The conductive bolt must not rotate while connecting the wire.
Industrial practices often reveal the use of steel washers and nuts in bolt-nut compression connections, which can increase contact resistance, particularly under high currents, leading to excessive heating and potential damage to adjacent insulation – a significant hazard.
2. Clamp Compression Connection:
For clamp compression connections, as shown in Figure 1.19, a structure suitable for high-current scenarios is used. The screws or bolts for the compression plate must include spring washers to prevent loosening – a crucial safety measure.
In such connections, the contact area with the cable core, when circular, should have an adequate curvature, ensuring sufficient contact area to reduce contact resistance and heating.
3. Other Connection Methods:
Besides these, equivalent methods like plug-in or soldered connections can be used in enhanced-safety electrical equipment.
For plug-in connections, a locking structure is necessary, often employed for internal wiring. Its locking mechanism ensures the plug remains secure during operation.
When using terminal blocks in plug-in connections, effective anti-loosening measures are necessary. The terminal block must prevent wire disconnection.
In soldered connections, tin soldering is commonly used for internal wiring. Wires should be secured at solder points to avoid unnecessary strain.
The primary concern in soldered connections is avoiding “cold solder” joints, which can cause operational issues and intolerable heating under prolonged energization.
In addition to these, other equivalent and reliable connection methods can be employed. All these measures aim to ensure reliable electrical contact at the connection points. High contact resistance can lead to increased temperatures, potentially creating a “dangerous temperature” ignition source. Loose connections, leading to wire disengagement and potential electrical discharges, are absolutely unacceptable.