Lower Connector Resistance for Improved Energy ManagementLower Connector Resistance for Improved Energy Management

A vast amount of energy is consumed by the electronic equipment which we design and rely upon in our daily lives. Electronic design engineers realize that an unavoidable waste of energy occurs when power is distributed throughout electronic equipment. As electrical current flows through conductors and connectors, unwanted heat is generated in proportion to the amount of electrical resistance encountered.

Lowering resistance in connector contacts and conductors can reduce the amount of heat generated and result in less lost or wasted energy. As a result, additional energy can be saved as cooling systems will have less heat to draw out of the equipment.

In the past, the primary metric for power connectors has been contact current ratings.
Looking ahead, contact resistance may become equally important. While it is true that contact resistance and contact current ratings are closely associated, contact current ratings cannot be used to quantify the energy consumed by contacts.

Current ratings are based on the temperature rise of a connector or contact at a specific current level. A connector design or test method allowing relatively rapid heat dissipation may yield a reasonable temperature rise, while a relatively high amount of energy is still being wasted.

Quantifying Performance
Within the connector industry, there are a variety of test methods used to quantify a particular performance metric. Different test methods can yield different values for the same metric. This lack of uniformity can be confusing to designers selecting connectors when trying to compare connectors offered by various manufacturers. Third-party sources, such as Underwriters Laboratory (UL) offer information to help sort through this information. UL Environment offers independent third-party assessment and verification of claims made by manufacturers. Once assessments are made, UL Environment issues an Environmental Claims Validated (ECV) Mark. This notation helps power connector users evaluate contact efficiency as it relates to energy consumption.

When it comes to UL information, it is important to know that contact resistance is used by UL Environment as the metric to determine the relative efficiency of connector contacts.

As an example of the process by which UL Environment assesses connectors, Positronic recently received an ECV for its VPB series size 16 power contacts. The ECV lists the average contact resistance for the contacts contacts at less than one milliohm each. This low contact resistance is achieved by use of high conductivity contact materials. In addition, Positronic's large surface area (LSA) contact system is used as the interface between male and female power contacts in VPB series connectors.

The VPB series was designed for use as the Zone 1 power connector in AdvancedTCA
(ATCA) telecommunication computing systems. Zone 1 connectors provide power from
backplanes to front boards in ATCA chassis. However, the low contact resistance of the VPB series provides energy savings opportunities in any application using this connector.

The Formula for Energy Savings
The following formula is used to verify the energy savings of a lower resistance contact at a given current:

Power Consumption (Watts) = Current Flow2(Amperes2) X Contact Resistance (Ohms)

Contact resistance has a one-to-one effect on power consumption. If, the contact resistance is reduced by half, the power consumption is reduced by half.

Low resistance power contacts also provide benefits in systems sensitive to voltage drop. This is demonstrated in the following formula:

Voltage drop across contact pairs = Current Flow (Amperes) X Contact Resistance (Ohms).

Here again, contact resistance has a one-to-one effect. Reducing the contact resistance by half reduces voltage drop by half.

As higher energy costs and government legislation cause energy conservation efforts to intensify, it becomes increasingly important to consider the vast numbers of power contacts in electronic equipment around the world. Therefore, understanding how lower contact resistance can play a role in meeting energy conservation goals is an important piece of knowledge for any electronic design engineer.

Gino F. Nanninga is vice president of sales for Positronic Industries Inc.