There is a vast array of electrical power connectors available and choosing the right one for your project will impact design restraints, manufacturability and maintenance.
Some of the elements to consider when selecting the most appropriate power connector include:
- Current rating (current density) and operating voltage
- Connector size (circuit density) and pitch
- Engagement force and locking
- Polarisation
- Mounting configuration
- Materials & Construction – Contact and housing type
- Durability (cycles)
Leotronics stocks a range of 3.0mm (Molex Microfit) power connectors and 4.2mm (Molex Mini-fit junior) power connectors in 2-24 circuit options with a range of configurations available.
The most popular configurations are listed on our connector catalogue with a unique series ID number. You can view the series’ specification sheet, which provides a summary of how each component rates on the above elements.
To help you consider how the specifications relate to your application, here is an overview of the main features to consider when choosing the most appropriate power connector for your project.
Current Rating
The stated amps-per-circuit rating is the maximum amount of current that can pass through a mated connection without giving rise to a significant level of temperature rise.
The current rating decreases as the number or density of circuits increases and also depending on the gage of the wire and mounting technique. For example, Leotronics series 6740 4.2mm pitch power receptacle (equivalent to Molex Minifit Junior) are rated up to 9A for two circuits, dropping to 8A for four circuits, and 7A for eight and 6A for 10 or more.
The smaller 3.0mm pitch power connectors (equivalent to Molex Microfit) are current rated to a maximum of between 5A – 7A.
In addition, there is a maximum voltage rating; our 4.2mm and 3.00mm power connectors are rated for up to 600V A/C.
Connector Size
As the trend for downsizing peripherals and equipment continues, electronic connector size continues to be an important factor.
Different formats of connector offer different circuit densities, although as noted above this can affect the current rating.
The arrangement of the circuits can also impact upon space efficiency depending on your design with the option to arrange circuits in a single or dual-row. For example, the series 6737 could provide a 4-pin 4.2mm pitch power connector solution using a single-row side entry whilst the series 6746 offers the same side-entry option but in a dual row (2 x 2 circuit layout).
Pitch is a measure of the spacing between the circuits and is measured from the centre of the circuit contact pin to the centre of the adjacent contact pin.
Engagement Force and Locking
In high-vibration environments, such as cars, connectors with a positive locking mechanism may be preferential to avoid accidental disconnection. Although a positive lock also requires some form of unlocking action, such as ‘ears’ on the side of the connector plug to enable disengagement from the panel cut out.
The engagement force for a connector is the amount of force required for each circuit multiplied by the number of circuits. The more circuits in a connector, the harder it will be to make the mating connection between the male and female elements.
Therefore, as the number of circuits increase, it is more important that the connector is rated as a low-engagement force, otherwise this could become an issue during the manufacturing process, and may even result in damage if excessive force is required.
Configuration
Connectors are available in numerous mounting configurations. The available configurations relate to:
- The way the connector is mounted – eg free hanging, panel or board mounted
- The angle between the connector and the attachment – vertical, horizontal or right-angled (side entry)
- How the connector is attached to a board – eg solder, pegs
- Polarisation – this is when the housing is designed to ensure that the male and female components of the connector can only be connected in one orientation and not upside down.
A right-angled 12-circuit connector without and with mounting pegs
Materials and Construction
The construction relates to the materials the housing and contact pin are made of.
The housing needs to provide insulation resistance, heat resistance, be lightweight and may be available in a choice of colours.
All of our housings are based on a flame retardant nylon 6/6 compound with 94V-0 and 94V-2 versions available for most series options. The UL94V-0 is the more flame retardant of these two.
The contact pin is a piece of metal which completes the connection. The pin can be cylindrical or square. Most of our power connector contacts are made from brass plated with tin as standard. The brass offers strength and conductivity and the tin plating offers protection against oxidisation, resulting in a low and stable resistance. If you require gold-plated contacts, please let us know as this is an option on most connectors.
Due to the soft nature of tin, it if becomes damaged through repeated connection and disconnection, the exposed areas of brass underneath can oxidise resulting in lower conductivity.
Mating Cycles
As explained above, the softness of the tin coating on power connector contact pins can lead to damage over time. As a result, power connectors are rated for ‘mating-cycles’ the number of times the connection can be made and disconnected before performance is affected.
As the 3.00 and 4.2mm power connectors tend to be used internally within pieces of equipment such as computers or car stereos, they are rarely – if ever – disconnected and therefore a low mating cycle rating is acceptable and the standard rating of 25 cycles usually far exceeds the actual requirement. If you require a higher mating cycle rating, gold-plating or using pins constructed from a non-corrosive metal would be recommended.
If you can’t find the right power connector your project, please contact us. Leotronics are the UK and Europe distribution agents for Cvilux, one of the world’s leading manufacturers of high-quality UL approved electronic components for the automotive, consumer electronics, computing and networking and optoelectronic industries and offer a far wider range of connector options than we are able to list of on our catalogue.
In addition, we are able to develop custom connectors which can be manufactured to your exact specification (MOQ required – contact us for details).