technical of BIMETALLIC CONNECTORS
1. Ultimate Tensile Strength (UTS)
1. Aluminum portion (EC/99.5% purity, per IS 5082):
I. UTS: ≥90–120 MPa (soft Al) or ≥150 MPa (for hard-drawn or alloyed Al)
2. Copper portion (Electrolytic Cu, per IS 613):
I. UTS: ≥200–250 MPa
3. The bonded zone (Cu–Al interface) is tested to withstand ≥70% of Al UTS to ensure integrity
2. Working Load / Safe Working Load (SWL)
1. SWL is derived from UTS, typically 1/3 of UTS as safety margin
2. Example:
I. Bimetallic lug for 70 mm² conductor can safely withstand 1.5–2.5 kN axial pull
II. Ensures connector can sustain:
Pull-out forces
Thermal expansion/contraction
Mechanical vibration
3. Conductor Diameter Compatibility
1. Designed to accommodate:
I. Copper cables: 6 mm² to 400 mm²
II. Aluminum cables: 6 mm² to 500 mm²
2. Bimetallic connectors are precision-bored or slotted to tightly fit:
Solid conductors
Stranded conductors (ACSR, AAAC, Cu)
3. Available in both DIN and IS-standard cable sizes
4. Slip Strength:
1. Bimetallic connectors must hold conductors firmly without slippage under:
I. Vibration
II. Fault current surges
III. Load cycling
2. Typical slip strength: ≥3–6 kN, depending on size and torque applied
3. Enhanced by:
I. Serrated internal bores
II. Proper crimping or bolting
III. Use of contact paste or inhibitor grease
5. Temperature Withstanding Capacity:
1. Continuous operation: Up to 90°C
2. Short-term fault condition: withstands up to 250–300°C
3. Designed to handle:
I. Current surges (25–35 kA for 1 sec)
II. Thermal expansion without bond separation or contact failure
6. Corrosion Resistance:
1. Al-Cu interface is protected via:
I. Friction welding (no galvanic gap)
II. Tin plating (8–15 µm thick)
III. Use of inhibitor paste at installation
2. Passes:
I. Salt spray tests (ASTM B117) ≥ 500–1000 hours
II. Humidity and SO₂ chamber tests for industrial atmospheres
7. Impact & Fatigue Strength:
1. Withstand:
I. Mechanical vibration from wind or load cycles
II. Pulling, twisting, or hammering during installation
III. Thermal fatigue from daily temperature variation
2. Crimped or bolted versions must resist 10,000+ vibration cycles without loss of contact pressure
8. Mechanical Endurance:
1. Design life: ≥30–40 years
2. Endurance tested under:
I. Cyclic thermal loading
II. Electrical current cycling (IEC 61238-1 Class A)
III. Outdoor weather exposure
9. Design Safety Factors:
1. Mechanical safety factor: ≥2.5–3.0
2. Electrical safety factor:
I. Low contact resistance (≤ 100 micro-ohms)
II. Sufficient cross-sectional area to handle rated current
III. Connector performance must exceed conductor fault ratings
Top 5 Quality Assurance
1. Type Tests as per IEC 61238-1 / IS 8309
a. Conductor pull-out test
b. Current cycle test (heating/cooling under load)
c. Short-circuit test (25–35 kA for 1 second)
2. Material Composition Verification
a. Copper portion: ≥99.9% purity verified via spectrometry
b. Aluminum portion: EC grade or alloyed Al as per IS 5082
c. Bond joint between Al–Cu must be:
I. Void-free
II. Free from intermetallic corrosion or delamination (checked by dye-penetrant or ultrasonic inspection)
4. Corrosion Resistance & Environmental Testing
I. Salt spray test: ASTM B117, minimum 500 hrs
II. Moisture + sulfur dioxide chamber test (for industrial zone suitability)
III.Optional: Soil burial test (for underground-rated lugs)
5. Marking, Traceability & Compliance Documentation
a. Each connector is marked with:
I. Manufacturer name/logo
II. Conductor size range
III. Batch/heat number
b. Supplied with:
I. Routine Test Certificate
II. GTP (Guaranteed Technical Particulars)
III. ISO 9001/14001 certification
IV. Optional: Type Test Reports from ERDA/CPRI