How To Connect Bimetallic Terminal Blocks To Undersized Cables Successfully
Connecting a bimetal cable lug to an undersized conductor causes loose joints, overheating, and electrical failure. When the wire diameter is smaller than the barrel inside diameter, crimping tools cannot create a gas-tight seal. Operators must use specific adaptation techniques to ensure conductivity and mechanical strength.
Step-by-Step Adaptation Methods
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Using Copper Reduction Sleeves: Insert a copper sleeve over the stripped conductor to increase the diameter before insertion into the bimetal terminal lug.
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Selecting Narrow-Barrel Lugs: Replace standard sizes with a bi metallic cable lugs variant designed for reduced core cross-sections.
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Employing Correct Hexagonal Dies: Utilize smaller crimping dies that match the sleeve thickness rather than the original terminal size.
Dimensions for Cable Accommodation
| Nominal Cable Size (mm²) | Sleeve Thickness (mm) | Crimp Pressure (kN) |
|---|---|---|
| 16 | 1.5 | 50 |
| 25 | 2.0 | 60 |
| 35 | 2.5 | 60 |
Execution Practices
Strip Length Measurement
Conductor stripping must equal the barrel depth plus two millimeters. This allowance prevents the bimetallic terminal blocks from pushing wire strands back during compression.
Anti-Oxidation Compound Application
Oxide inhibiting paste must fill the joint. This compound breaks down aluminum oxide layers fields upon compression and seals out moisture, preventing galvanic corrosion inside the bi metallic cable lugs.
Mechanical Pull Testing
Every modified connection requires a calibrated pull test based on international electrical standards. Technicians must verify that the adapted joint withstands the specified tensile force before final installation.
