Connectors

Connectors are pieces of equipment that must NOT be plugged in or disconnected when used as intended, i.e. under electrical voltage (or technically under load). When connecting or disconnecting a connector under load, sparks and (briefly) high temperatures result which could destroy the contact surface and lead to the total failure of the plug connector.

Connectors may only be connected or disconnected when there is no current and voltage.

The soiling level is a numerical value and indicates the environment for which the connector has been developed and tested. Soiling level 3 is typical for industrial environments, while soiling level 2 is typical for households.

Soiling levels and their significance

Soiling level 1

• There is no soiling or only dry, non-conductive soiling. The soiling has no influence on the properties of the connector. 
• Open, unprotected insulation in air-conditioned or clean, dry rooms.

Soiling level 2

• Only non-conductive soiling occurs. Occasionally, however, temporary conductivity due to condensation must be expected.
• Open, unprotected insulation in residential, retail and other commercial premises, fine mechanical workshops, laboratories, test areas, medical premises.

Soiling level 3

• There is conductive soiling or dry, non-conductive soiling that becomes conductive because condensation is to be expected.
• Open, unprotected insulation in rooms of industrial, commercial and agricultural plants, non-heated warehouses, workshops, boiler houses.

Soiling level 4

• Contamination results in constant conductivity caused by conductive dust, rain or snow.
• Open, unprotected insulation in maritime or mining applications

EPIC® connectors are generally designed for soiling level 3 and therefore have high safety reserves, even if the connector is wet or dirty inside. The high reliability of EPIC® results from high quality materials and manufacturing expertise.

The rated voltage is the voltage according to which connectors are rated. It indicates at which voltage a connector can be operated continuously and without impairing its performance. 

Dependencies:

• The rated voltage depends on the defined soiling level. If a connector was tested for soiling level 1, the rated voltage given in the technical data is significantly higher than if it was tested for soiling level 2. 
• The rated voltage depends on the insulating properties of the materials used and the creepage distance (the distance between contacts on a surface).
• The rated voltage depends on the clearance (the distance between contacts through air). 
• The rated voltage depends on the pole configuration, i.e. the number of contacts. The more contacts are installed in a connector, the lower the rated voltage.

The rated current is the maximum current determined by the manufacturer that can flow continuously through all contacts of the connector without the upper temperature limit being exceeded. The rated current is specified at an ambient temperature of 40 C. It is determined for the largest conductor cross-section that can be connected to the connector.

The rated current depends on the size of the contacts in the connector. As the contact diameter increases, so does the current.

Contact layers made of high-grade materials are essential to ensure a secure electrical connection over the long term. The contacts are usually coated using galvanic processes. In order to achieve a durable coating, the following requirements are placed on the base material and its contact layers: LAPP primarily uses silver (Ag) and gold (Au) for surface coating.

Silver has the highest electrical conductivity of all metals. The passivisation of the silver surface delays the formation of an oxide layer and reduces the insertion and pulling forces. A brownish to black oxide layer of silver sulphide (Ag2S) forms due to sulphur or substances containing sulphur in the ambient air. However, this layer can be broken during the plugging process or is broken at high currents, so the required electrical conductivity is maintained. 

Gold is the most resistant precious metal. The formation of oxides and sulphides can be ignored. Gold contacts are characterised by low insertion and pulling forces. They are mainly used for the transmission of signals with low current and voltage values. 

EPIC® products only use high-quality stainless metal alloys for coating the contacts.
When selecting a connector insert, the insert that can accommodate at least the number of contacts required for the plug connection must be selected. Plug connector inserts containing more contacts are also selected in the application. This means that the same plug connection system can often continue to be used when the application is expanded.

Each time a connector is connected or disconnected, this represents one plug cycle.  If a connector is subjected to too many plug cycles, this will have negative effects on the contact resistance and also on the coating of the contact area. When determining the maximum number of plug cycles, a test is carried out to find out how many plugging and disconnecting actions cause the contact resistance to increase to an unacceptable level. It must not increase by more than 50% or exceed a maximum of 5 mOhm.

Owing to the high-precision manufacture of the contacts and the choice of contact materials, the EPIC® connector has a very long service life.

Electromagnetic compatibility, or EMC for short, is the ability of electrical equipment to function satisfactorily in its electromagnetic environment without impermissibly influencing the environment, which also includes other equipment, or being influenced by it (DIN/VDE 0870, Part 1). 

In industrial environments, the interference frequencies normally lie in the frequency range below 100 kHz. In this frequency range, the most important factor is low-impedance, large-scale, 360° screening. 

Plug connectors that are protected from electromagnetic interference have housings with a metallic, conductive surface, a good electrical connection to the mating component and are equipped with a cable gland that allows the cable shield to be electrically connected to the housing.

EMC plugs are mainly used in the area of circular connectors. For rectangular connectors, the EPIC® ULTRA housings have been specially developed to meet these requirements.

Coding is an arrangement which prevents connectors which are identical other than their different polarisation from being mixed up, i.e. incorrect plugging and cabling. This is suitable if two or more identical connectors are attached to the same device.

Coding can be performed with a coding key or coding insert, or using coding pins that can be screwed into the housing. With EPIC®, there is a coding option optimised for every connector system, such as coding-capable inserts and housing, as well as pre-coded circular connectors.