General technical information on circular connectors

The air gap is the shortest distance in air between two conductive parts.

The clearances in HUMMEL products are dimensioned for altitudes up to and including 2000 m above sea level (NN). For air distances over 2000 m, altitude correction factors apply, please contact our technical specialist.

The creepage distance is the shortest distance along the surface of an insulating material between two conductive parts.

Plug devices are plug-in connectors which, when used as intended, live or under load, may be plugged in or disconnected. Sockets are also known as CBC (connector with breaking capacity). A classic example from the household is the SCHUKO plug.

Connectors that may not be plugged in or disconnected under load or live when used as intended are also called COC (connector without breaking capacity).

HUMMEL connectors are usually classified as COC, so they must not be connected or disconnected when live!

The derating curve (current-carrying capacity curve) describes the maximum permissible power loss of an electrical or electronic component as a function of its ambient temperature below its upper limit temperature (see above). The configuration and wiring of the component is important for this (number and cross-section of the energized conductors in connectors).

• The heating is measured as the temperature difference (∆T) to the environment at nominal current.
• The base curve describes the real, measured temperature at the warmest point of the component at the corresponding ambient temperature.
• The derating curve is calculated (in accordance with EN 60512-5-2) by reducing the current value by 20% of the base curve.
• The rated current limits the current to a maximum value.

Example: In the curve, the component should only be operated up to 40 A at an ambient temperature of 100°C without exceeding the upper limit temperature.

The degree of pollution is a numerical value that indicates the expected pollution of the microenvironment and is a parameter when dimensioning the air and creepage distances in electrical equipment. It describes the possible contamination of an open, unmated connector in a certain environment. The EN 60664-1 standard distinguishes between four categories:

• Pollution degree 1: No pollution or only dry, non-conductive pollution occurs. The pollution has no influence.
• Pollution degree 2: Only non-conductive pollution occurs. Occasionally, however, temporary conductivity due to condensation must be expected. (Typical for households, business premises, laboratories or test areas.)
• Pollution degree 3: Conductive pollution occurs or dry, non-conductive pollution that becomes conductive because condensation is to be expected. (typical for industrial companies or workshops.)
• Pollution degree 4: There is permanent conductivity, caused by conductive dust, rain or moisture.

If connectors are used with a higher degree of pollution, the voltage values must be reduced. Please contact our technical specialists.

UL94 is a standard used by the American test laboratory Underwriters Laboratories, in which the burning properties and fire safety of plastics are examined. The UL 94 HB (Horizontal Burning) test tests the burning of a horizontal piece of plastic and the more demanding test UL 94 V (Vertical Burning) tests the burning of a vertical piece. The exact explanations about the systems used, the conditions and the test system can be found in the written UL 95 standard.

Example: UL identification for flammability UL 94 V (test of vertical combustion)

Functional earth (FE) is an electrical conductor, to ensure the functions and thus the regular operation of systems and devices.

Functional earth conductor: Grounding conductor for the purpose of functional grounding.

Functional ground: Earthing of a point or several points in a network, a system or an operating device for purposes other than electrical safety.

With regard to their suitability for various environmental conditions, electrical equipment is designed in accordance with EN 60529 with suitable degrees of protection expressed by IP codes. The abbreviation IP stands for Ingress Protection (protection against ingress). The letters IP are followed by 2 digits describing protection against foreign bodies/contact (st digit) and protection against water (2nd digit).

To ensure the IP protection class and the necessary contact overlap, the cable connector and the coupling connector must be plugged in and locked up to the stop.

Upper and lower temperatures that do not damage the materials are referred to as limit temperatures. In between lies the operating temperature range (e.g. -40 ... +125°C)

The lower limit temperature is the lowest permissible temperature at which a connector or plug device may still be operated

The upper limit temperature is the highest permissible temperature at which a plug connector or plug device may still be operated. It is equal to the sum of self-heating (contact heating and heating of the cable) and the maximum ambient temperature.

An insertion and removal process of connectors is referred to as a mating cycle. The number of mating cycles is an important parameter for plugs and connectors. It defines the service life of a connector, which it can complete without any loss of transmission quality. The quality of the contact surface in particular has an influence on the number of mating cycles. The use of high-quality and durable contact coatings reduce surface abrasion during the mating process.

In general, contact overlap or mating security in connectors refers to the possible overlap area of pin and socket. The larger this area, the more reliable the connection due to the higher possible tolerance compensation.

At HUMMEL, in order to guarantee the IP protection class and the necessary contact coverage, cable and coupling connectors must be plugged in and locked as far as they will go.

The overvoltage category is a (Roman) numerical value that defines a condition with regard to transient overvoltages for equipment that is fed directly from the low-voltage network:

• CAT IV: Equipment for use at the connection point of the installation (electricity meters, primary overcurrent protection devices, etc.)
• CAT III: Equipment in fixed installations and for those cases in which special requirements are placed on the reliability and availability of the equipment. (Switches in permanent installations and equipment for industrial use with permanent connection to the permanent installation)
• CAT II: Energy-consuming equipment that is fed by the fixed installation (household appliances, portable tools and other household appliances and similar devices). [However, if such devices are subject to special requirements in terms of reliability and availability, CAT III must be used.]
• CAT I: Circuits that are connected to the mains but suitable measures have been taken to limit transient overvoltages.
• Without CAT information: circuits that have no direct connection to the network. Example: In battery operation or behind a transformer that offers double / reinforced insulation (e.g. devices of protection class 3 - operation with protective extra-low voltage, car electrics, controls, PLC, motor controls)

Protective conductor (PE) is an electr. conductor for the purpose of safety, for example to protect against electric shock. It is also known as the earth conductor, or “earth” for short. Task in electr. Systems is the protection of living beings in the event of a failure.

PE conductor: Protective conductor for the purpose of protective earthing

Protective earthing: earthing of one or more points in the network, in a system or in equipment for the purpose of electrical safety.

The rated current is the current value, preferably at an ambient temperature of 40°C, which the connector can carry continuously (without interruption) and which flows simultaneously through all contacts connected to the largest fixed conductor without exceeding the upper limit temperature.

When considering the current carrying capacity of the connector, the current carrying capacity of the lines and cables used must be taken into account. This is primarily dependent on the permissible limit temperatures (see below), but also on the cross-section of the conductors and their bundling and installation situation. To this end, the manufacturer's instructions or standards such as: DIN VDE 0298-4 or IEC 60364-5-52 must be observed. Here are some extracts from DIN VDE 0298-4:

Tables according to installation type:

Conversion factors for different ambient temperatures:

The rated impulse voltage is the value of a withstand impulse voltage that is specified by the manufacturer for a piece of equipment or for a part of it and which indicates the specified withstand capability of its associated insulation against transient overvoltages.

The level of the value is a measure of the minimum required air gap in the equipment.

The rated voltage is the specified value of the voltage to which the operating and performance characteristics are related. A connector can have more than one value of the rated voltage for the different voltage systems.

HUMMEL connectors can be used for DC (V=) and AC voltage (V~). For these cases, the rated voltage of the effective value of the maximum rated voltage line to neutral (U_L-N). In 3-phase three-phase systems (V3~), the rated voltage is specified as phase voltage / conductor to conductor (U_L-L).

In earthed networks (T_N, T_T, T_N-C, T_N-CS, ...) the voltage conductor to earth (U_L-PE) is √3 less than the phase voltage (U_L-L). In ungrounded networks, the conductor to earth voltage (U_L-PE) is calculated to be the same as the conductor to conductor voltage (U_L-L), i.e. not reduced by √3 because the star point (N) is not connected to earth (PE) is! This is important for dimensioning the clearances.

The test voltage is the voltage that a connector has to withstand under certain specifications without a voltage surge or voltage breakdown occurring over or through the insulation and corresponds at least to the withstand voltage in EN 61984.

The value of the test voltage is higher than the rated voltage and is used to verify the insulation capacity of the connector.