Presentation on theme: "1 CTIS # 29954 Prepared By John Yurtin Updated 2-3-2005 Connection Systems Training Electrical Performance & De-Rating."— Presentation transcript:
1 CTIS # 29954 Prepared By John Yurtin Updated 2-3-2005 Connection Systems Training Electrical Performance & De-Rating
Delphi Confidential2 Having a good technical understanding of the expectations and performance of connections can help you properly apply them within the vehicle. Electrical performance should be clearly understood since it is the basic function of our products. This training help you understand electrical performance and how it applies to specific applications. Excellence Performance Goal: Do it right the first time, every time Method: Innovation and continuous improvement
Delphi Confidential3 Contents Understanding De-Rating Crimp-To-Crimp Resistance Example Various Specifications Its Not That Simple! Cable Examples Actual Failure Analysis What Do I Need To Know? Resources
Delphi Confidential4 Understanding De-Rating De-Rating limits the circuits current to assure that heat generated does not exceed the limits of the connection materials. The temperature rise generated by the current + the ambient temperature must not exceed the material limits Temp Rise + Ambient < Lowest Material Limit Example: If cable insulation is limited to 135 0 C and ambient is 125 0 C then there cannot be more than 10 0 of temp rise.
Delphi Confidential5 A mating set of terminals is simply a resistance –We call this Crimp-to-Crimp resistance –It is measured before and after testing –It unfortunately can vary over the life of the product The mated terminals replace the resistance of an equal length of wire. 35 mm length 35mm of 16 ga cable is.53 m/ohm Crimp-To Crimp Resistance
Delphi Confidential6 Crimp-to-Crimp Resistance Interface resistance Bulk resistances Two Crimp Resistances Crimp-to-Crimp resistance at the end of testing is usually only several milliohms and varies with design, size and materials –Example - 280 Metri-Pack 1.1 m/ohms But, many specifications allow resistance to be up to 10 m/ohms or more As Current flows through the terminals, they heat up (I 2 R=P) Heat is dissipated through: –Conduction down the core of the wire (approx 80%) –Radiation to other bodies –Convection through air = Crimp-To Crimp Resistance
Delphi Confidential7 Example In a connection system, there is some weakest link with regard to temperature, e.g. maybe the cable insulation If the ambient temp is 125 0 C and we start passing current, the terminal is going to heat up based on I 2 R effect Once the ambient plus the rise due to current reaches the insulation limit,then we have a max operating current. Limitations (example): Cable Insulation: 135 0 C Terminal Plating: 175 0 C Conn Body Material: 150 0 C Copper Core: 200 0 C Silicone Seals:
Delphi Confidential8 u Cross Link Cable is good for 135 0 C, so in a 125 0 C ambient we can only allow a 10 0 rise. u If we rate terminals for maximum cable current then: For 16 ga cable, the max current is (for example): 15 amps per SAE J 2030 (*29.2 0 Temp Rise) 13 amps per Deutsch Spec (22.2 0 Temp Rise) u Because you cant exceed the max rating of the cable insulation, you need to limit the current … …again, this is called De-Rating. * Calculated Values Example
Delphi Confidential9 Average Crimp to Crimp Resistance Values " Micro 64 gold plated 5.5 m Metri-Pack 150 "unplated 8.5 m " Metri-Pack 150 tin plated 2.7 m " GT 150 tin plated 4.0 m " Metri-Pack 280 " unplated 1.8 m " Metri-Pack 280 tin plated 1.1 m " GT 280 tin plated 3.0 m " Metri-Pack 480 " unplated 2.5 m " Metri-Pack 480 tin plated.65 m " Metri-Pack 630 tin plated.45 m " Metri-Pack 630 " unplated.50 m " Metri-Pack 800 tin plated.40 m It is important to understand that there is no one resistance for any set of terminals, The resistances vary depending on the test and test sequence.
Delphi Confidential10 SAE/USCAR Specification Temperature Rise Test Test at 23 0 C in open air, not in connectors Increase the current in increments until: a) The temperature of any terminal interface exceeds a 55 o C rise, or the maximum temperature recommended by the terminal manufacturer, whichever is lower. b) The Total Connection Resistance of any terminal interface exceeds... (10 m for 1.5mm Terminals) Plot the temp rise curves for each wire size. These graphs are NOT to be used for actual terminal application in a vehicle.
Delphi Confidential11 ISO 8092 Specification Really has no requirement for specifying max current capability! Temperature Rise Test Test in connectors at 23 0 C (room temp) Test currents for each cable size are found in the specification. (13.5 A for 1mm 2 cable) A current reduction coefficient is applied for multiple connectors. The temperature shall not exceed 40 0 C rise Note: The temperature rise shall not be used as a guide to the capability of the connector to operate at elevated ambient temperatures. Current Cycling Apply 500 cycles, each 45 min current on, 15 min current off Current is specified by the manufacturer Resistance not to exceed 30 m or 200% of initial value, whichever selected by supplier and user. (1.5mm terminals)
Delphi Confidential12 u If several circuits within a connector are powered simultaneously, their heat can add requiring additional de-rating. u Most circuits are not continuously powered, but rather have cyclic currents (on/off cycles). u In multi-way connections, and in wire bundles, simultaneous powered circuits can add up heat, or, in the same way, harness bundles can act as heat sinks. u In device connections, the device can be a heat sink or a heat source complicating the de-rating And Its Not That Simple!
Delphi Confidential17 Terminal Temperature Tool (Intra-Net)
Delphi Confidential18 Contact resistance increases (next slide) Excessive heat is generated weakening the contact Low contact force results in even greater resistance and heat Temperature reaches limits of the plastic Eventual total circuit failure Actual Resistive Failure Example
Delphi Confidential19 u Wrong application of the connection u Wrong terminals u Wires too small u Unexpected duty cycle u Poor Crimps u Improper fusing or circuit protection u Environmental corrosion of the terminal interface u As a rule of thumb, oxidation and stress relaxation rates double with every 10 O C rise in terminal temperature. u High resistance from worn out motor What Causes Resistance Failure?
Delphi Confidential20 So What Do I Need To Know? Understand the complete circuit in which the connection performs –Know for sure what the expected worst case current will be. –Is the current steady state or intermittent? –Fusing and circuit protection Should the system be sealed? Understand the real limits of the connection. Use the prediction tools Look at the actual validation test results Perform testing if necessary
Delphi Confidential21 Resources Product Data Sheets Connection Systems E-Catalog Product Handbook Electrical Performance Programs On-Line Actual Validation Test Reports So What Article George Drew – Contact Physics Expert Product Line Managers