Case study: Sequential mating connector systems link portable power-distribution equipment

Outdoor applications such as dockside and riverside power plants, sporting events and amusement park rides often require the use of a mobile power generator linked to a low voltage network. These applications require extremely high power output, and the use of standard connectors was once a common solution for mating high-power cables and connectors to generators when powering outdoor equipment.

However, not only are these power connectors connected to large, heavy cables, but the use of individual connectors as a solution also more often than not overlooked fundamental safety concerns when applications required reliable connections for field installation of power-distribution systems such as mobile generators. This is both for the personnel operating the generator and the reliability of the outdoor equipment itself.

For example, while individual power connectors often feature IP2X finger protection, and the connector contacts are each sealed to IP65 or IP67 specifications to combat environmental elements and further ensure reliability of the equipment, without the presence of color-coding or keying on the connectors, the possibility of mis-mating the connectors or connecting the wrong line is significant. Similarly, unauthorized connection or disconnection also poses a risk, particularly in an outdoor environment such as a theme park where generators and cables are within access of patrons.

Figure 1: ITT VEAM’s Power Lock connectors are designed for field installation power distribution systems.
(Click on image to enlarge)

By the same token, working with continuous current upwards of 600 amps in live connector contacts poses a significant safety concern to field operators. Without proper safety mechanisms, lockings, and codings, equipment can shut down, be interfered with or, worse yet, a field operator can be shocked or electrocuted, causing serious injury or even death.

From carnivals, to sporting events, to outdoor television broadcasts and theaters, to alternative-energy installations, and in many heavy industrial environments such as construction sites, OEMs are more frequently realizing that they require comprehensive connector systems to meet safety, reliability, power, and ease-of-use requirements when connecting to mobile power generators.

Sequential Mating Solutions
As a result of these technical issues, constraints and safety concerns, connector manufacturers have developed high-power sequential-mating connector solutions with built-in safety and convenience design elements to meet the varied needs and concerns associated with outdoor equipment.

Some initial sequential-mating systems developed many years ago were available as either a panel source or a panel drain, and featured cam covers on each of the panel connectors to ensure that the proper sequence of Ground, Neutral, Phase 1, Phase 2, and Phase 3 were adhered to, thus preventing accidental electrocution through improper grounding contact. Once connected, the system could then be secured by a keylock, guaranteeing that it could not be accessed by unauthorized personnel.

As an additional security measure, the keylock on some such connector systems could then be hooked up via a microswitch to a circuit breaker. If the keylock were disabled, the circuit breaker would trip, isolating the sequential mating unit from the main power supply, thus preventing disconnection while under load. A primary keylock could also be employed to prevent unauthorized connection to the power cables.

Figure 2: The NRG sequential mating system was one of the initial sequential mating connector systems designed for use with mobile power generators
(Click on image to enlarge)

More recently, connector manufacturers have built on the success of original sequential-mating systems, such as the NRG mentioned above, by developing smaller, more cost-effective sequential-mating connector systems for linking generators to low-voltage networks. Offering the same sequential-mating functionality (ensuring ground is connected first, which is also vital in applications where fast installation is required) as original mating systems such as the NRG, some of today’s sequential mating boxes are housed in a 50% smaller profile than original designs and utilize only 2U of rack space in a 19-inch rack.

This “box” type system is also organized in the rack upon installation, further minimizing installation time and effort and simplifying the connection for less experienced operators. The connectors in this system are also available in 400 A and 660 A versions, providing significant flexibility to the customer in terms of the amount of current employed for each application. Utilizing a sequential-mating system also makes it easier to connect to different sources of portable power, as it is not necessary to hardwire or connectorize each individual connection.

In addition to the size reduction of the rack space made possible through this type of integrated system, there are also many safety features available with today’s sequential mating power connector systems, including IP2X finger protection, UL94-V0 materials, and 3-phase color coding to meet European, North American and Australian standards, while at the same time preventing incorrect mating and de-mating. With all of the people that work together to host a sporting event such as the Olympics, a concert, or even a political event–government agencies, municipal workers, private contractors and even volunteers–having a simple-to-understand, color-coded system enables a safe installation by less experienced technicians. Sequential mating systems not only ensure a safe connection to the power panel, they also eliminate the possibility of connecting the wrong line.

It is also common for such power-connection systems to feature a secondary locking mechanism that prevents unauthorized disconnection. In some designs available on the market, the secondary lock also activates a micro-switch that joins a two-pin connector on the back of the unit to a circuit breaker or alarm circuit to provide additional safety and security of the connection.

In terms of sealing for environmental reliability, today’s sequential-mating power-connector systems are often offered fully sealed to IP65 specifications with a lid covering the connector ports to protect against the ingress of dust, dirt and water; or are available in a standard configuration that is sealed only when the connectors are mated. Sealing the entire mating system as opposed to each individual connector provides a much more efficient solution to combating environmental elements.

Figure 3: The PowerLock Box sequential-mating system from ITT Interconnect Solutions provides the safety and reliability necessary for linking low-voltage networks to portable power-distribution systems
(Click on image to enlarge)

Additional enhancements to some sequential-mating power-connector “boxes” include a flange to provide simple and secure sealing into equipment panel cut-outs. Often available in lidded and non-lidded versions, the PowerLock Box from ITT Interconnect Solutions –which has become the industry standard for power connections at outdoor sporting and entertainment events–now incorporates a flange with an extended front panel measuring 107 mm, providing a seal around the entire box. The flange also prevents tampering and unauthorized entry to equipment, ensuring security in public setting applications such as those mentioned above.

Major outdoor events with mass audiences use sequential mating connector systems to address power needs while also satisfying safety and security concerns. As the popularity of such connector solutions continues to grow and meet a number of high-power needs (particularly when it comes to connecting low-voltage networks up to 1500 VDC, to portable power distribution systems), the applications for their use will continue to expand.

Sequential-mating solutions are well-suited for, and implemented at, events such as the Olympics where there is a significant power requirement over a relatively short span of time, and other arenas, including supermarkets, automotive factories, and even military bases, are adopting the technology as a backup solution in the event of a power failure from the main power supply. While individual, standard connectors may cost less and can be adequate in terms of amperage and functionality, sequentially mated power-connector systems provide the safety, security and reliability that is essential to outdoor equipment.

About the authors
Mike Gardiner is a product manager at ITT Interconnect Solutions, and has more than 30 years of experience in the connector industry. Mike received his B.S. degree from Saint Louis University. Mike can be reached at mike.gardiner@itt.com.

Graham Oakley is a product manager at ITT Interconnect Solutions, and has more than 25 years of experience in the connector industry. Graham can be reached at graham.oakley@uk.itt.com.