Industrial Connector Selection Guide: IP Ratings, Locking Mechanisms, and Chemical Resistanc

When selecting industrial connectors, designers of power distribution systems must consider basic specifications such as voltage, current, operating temperature, and requirements for basic shock and vibration resistance. They also need to take into account factors like Ingress Protection (IP) ratings, locking mechanisms, chemical and corrosion resistance, and hot pluggability.

The IP ratings of industrial connectors are designed to ensure reliable operation under specific environmental conditions. They consist of two digits. The first digit indicates the level of protection against the entry of solid objects and dust into the connector, and the second digit represents the degree of protection against the entry of liquids into the interior. A "0" in either position means there is no protection.

The highest rating in the standard IP ratings is IP69. IP69-rated equipment is dustproof and can withstand high-pressure liquid and steam cleaning. The next level down is IP68, which is suitable for dustproof equipment and can withstand being immersed in water up to 1.5 meters deep for up to 30 minutes.

Examples of connectors with an IP68 protection rating include the Samtec ACR-16 and SBSX-75A sealed and waterproof connectors from Anderson Power Products. The ACR-16 is a 10-pin connector with a rated current of 11.6 A, and the SBSX-75A has two power pins with a rated current of up to 135 A and up to four signal pins. Both connectors also include locking mechanisms, although the styles of the locking mechanisms are different (Figure 1).

Figure 1: The ACR-16 (left) and SBSX-75A (right) connectors have an IP68 environmental rating and locking mechanisms (not to scale). (Image: Sager)

Locking Mechanisms

Locked or locking connectors are designed to prevent accidental disconnection and provide a safe and reliable connection. They are widely used in automotive, energy storage, industrial, medical, and other applications. For example:

The ACR-16 series are bayonet connectors that lock when mated and twisted. They can be plugged and unplugged with a 1/3 turn.

The SBSX-75A series uses latches, with stainless steel spring latches on the sides that snap firmly into place.

A variety of other locking/locking mechanisms are available, including:

Lever locking is a very common mechanism on industrial connectors. It can prevent the connector from opening and increase the tightness of the connection. The Hirose push-pull locking uses internal latches in the plug. When the two halves are pressed together, these latches retract and insert into matching grooves inside the socket. To disconnect, it is necessary to squeeze the connector body while pulling the two halves of the connector apart.

Screw locking uses threaded couplings to improve shock and vibration performance. Screw locking is used for both rectangular and circular connectors.

Chemical and Corrosion Resistance

Even for locked and sealed connectors, exposure to hydrocarbons and solvents in transportation, industrial, and mobile applications can reduce the degradation of standard housing materials. For these applications, the connector housings can be made of materials with chemical corrosion resistance.

Polycarbonate (PC) has good chemical resistance to dilute acids, neutral salt solutions, greases, oils, and detergents.

Polybutylene terephthalate (PBT) is suitable for applications where exposure to organic solvents, gasoline, and oils is expected.

The PC/PBT blend combines the best properties of the two polymers, with high chemical resistance, high impact performance, and excellent weather resistance.

The SB connector series from Anderson Power Products offers chemically resistant housings using a PC/PBT mixture. These connectors have a rated current of up to 280 A, an extended operating temperature range from -40 °C to 105 °C, and an environmental rating of IP64 (Figure 2).

Figure 2: The housing of this power connector is made of a PC/PBT mixture and has high chemical resistance. (Image: Anderson Power Products)

Hot-Pluggability

Modular systems can improve reliability by using hot-pluggable connectors. In other cases, service plug connectors (also known as cold plug connectors) are required to disconnect circuits and ensure the safety of workers in high-voltage areas.

Hot pluggability supports the insertion and removal of live connectors to maximize system availability. There are two hot-plug configurations:

Premating or make-first/break-last sequences the contacts so that they engage before the main power contacts. Premating is used to prevent overcurrent, short circuits, and ground faults.

Postmating or make-last/break-first sequences the contacts used for signal or auxiliary power positions to ensure that communication does not start or power circuits are not turned on until the power contacts are fully engaged.

The Powerpole connectors from Anderson Power Products are rated at 600 V, with a current of up to 350 A, and have a pre-connection feature. The flat wiping contact system has a large normal force and a large conductive area to minimize contact resistance. The sacrificial tip limits damage to non-conductive surfaces when plugged or broken under load. When plugged, the wiping design cleans the mating surfaces whether under load or not.

Cold-Pluggability

High-voltage applications (1,500 V+) are usually more concerned with operator safety than system uptime. In these cases, service plugs can be used for cold-pluggability to manually disconnect the power and protect the operator from high voltage.

The Hirose EM30MSD service plug includes power terminals rated at 1,500 V and 200 A and signal lines rated at 250 V and 1 A. These signal lines are interrupted to prevent hot pluggability when the bayonet locking mechanism is rotated to disconnect. When mated, the locking system also provides shock resistance to minimize the possibility of accidental disconnection (Figure 3).

Figure 3: When the EM30MSD cold-pluggable connector is unplugged, both the power and signal lines are opened to protect the operator. (Image: Hirose)

The multi-point contact design reduces contact resistance. The PBT housing of the EM30MSD service plug has chemical resistance, has an IP68 protection rating when mated, and is suitable for environmental protection.

When unplugged, the socket part has an IPX2 finger protection function, which reduces the risk of electric shock to the operator. The IPX2 design prevents solid objects (such as fingers) with a diameter greater than 12.5 mm and a length exceeding 80 mm from entering.

Custom Cable Configurator

Selecting connectors is an important task. So is designing cable assemblies using these connectors. Molex's Custom Cable Configurator simplifies this process.

Designers can use this online tool to quickly design customized cable assemblies. After the design is completed, the tool provides concept drawings, 3D models, samples, and quotations from Sager Electronics. Features and functions include:

Selection of power and signal connectors

UL-rated wire options

Support for dual-ended and single-ended designs

Options for bundling accessories and custom labels

Advanced features include a pinout configurator and automatically generated drawings and 3D models.

Selecting industrial connectors and designing cable assemblies that can provide power, protection, and reliability is a detailed process. It involves considerations of connector IP ratings, latch/locking mechanisms, and chemical and corrosion resistance.