Derating of Connectors


We know that electrical resistance creates heat when a current goes through it. The amount of heat is directly related to these two parameters. Electrical connectors always specify a working current which is defined by international, national or even industry specific standards that provide a maximum temperature rise (∆t) value allowed under working current. These are measured at the hottest point of the connector by using a very precise processes (usually EIA364-70 standard is followed). Different standards might allow different values for this maximum ∆t. For UL certification, Würth Elektronik chose to have a ∆t maximum of 30 K (UL1059 – Terminal blocks). Different standards can refer to different test procedures, the number of poles and especially ∆t value hence it is possible to find different current values within the standards (UL and VDE for example) for the same product.But what is the influence of the ambient temperature on the resistance? Should we limit the current when the temperature increases and especially when it is close to the maximum operating temperature allowed on a connector? We will try to answer these questions and give practical operating curves to be used with our connectors.

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