Appliance classes

Protection classes are used in electrical engineering to the classification and labeling of electrical equipment (eg, equipment and installation components ) with respect to the existing security measures to prevent an electrical shock.

General

The safety classes are for all electrical equipment is superior in DIN EN 61140 (VDE 0140-1 ) set.

There are four classes of protection for electrical equipment, the protective grades one through three are the most common. To identify the equipment with the relevant Class are provided symbols that are defined in IEC 60417. The use of protective measures in the various classes of electrical equipment is described in DIN EN 61140 (VDE 0140-1 ) :2007- 03, section 7.

The degree of protection is to be distinguished from the IP (Ingress Protection according to IEC 60529) classified protection. While protection classes define measures that protect against dangerous contact voltages, the IP protection classes describe the degree of protection of the housing against contact, foreign bodies and water.

Protection class 0

There is in addition to the basic insulation no special protection against electric shock. The connection to the protective conductor system is not possible. The protection must be ensured by the environment of the equipment. For protection class 0, there is no symbol; labeling is not provided. The protection class 0 should not be included in the future international standard. Such devices are not allowed in Germany and Austria.

Protection class I / protective conductor

All conductive housing components of the equipment are connected to the protective conductor system of the fixed electrical installation, which is at ground potential. Portable appliances with protection class I have a connector with a grounded contact, a plug with earthing contact or in Switzerland a three-prong plug. The protective conductor connection is designed so that it is prepared when the plug is inserted as the first and is separated in case of damage as the last (see leading contact ). The introduction of the connection cable into the device must be mechanically strain relief, while tearing out the wiring of the protective conductor must tear off last.

When a current carrying conductor contacts the housing connected to the protective conductor in the event of an error, usually arises a body circuit so that the circuit breaker (fuse) or an earth leakage circuit breaker trips and the circuit switched voltage-free.

At Altinstallation is still often the Classic zeroing to be found; it was also connected as a protective conductor with the protective conductor contacts of the sockets of the neutral ( zero potential ). This conductor is called the PEN conductor - a combined head of the protective conductor (PE ) and neutral ( N). For new installations, the classic zeroing is in circuits with less than 10 mm ² Cu/16 mm ² Al no longer allowed because it leads during interruptions of the PEN conductor, that the case of all connected on the relevant circuit protection Class I devices carry hazardous voltage.

The rightmost symbol stands for the taking place at Class I grounding, for protection class I itself there is no icon.

Protection class II / insulation

Apparatus with protection class II have reinforced or double insulation between the mains circuit and output voltage or metal housing (VDE 0100 Part 410, 412.1 ), and usually have no connection to the protective conductor. This protective measure is also called insulation II ( Secure Electronic separation). Even if they have electrically conductive surfaces so they are protected by reinforced insulation from contact with other live parts. Moving equipment of protection class II usually do not have a safety plug; for connecting plugs are used that have no grounding; at high currents, these are in Germany contour plug - plug versions that see a grounding plug similar. For small currents ( up to 2.5 A) so-called Euro plugs are used. If a cable is used with protective conductor, as this is an active conductor must not be connected to the housing and must be treated. (VDE 0100 Part 410, 412.2.2.4 ) Example: industrial vacuum cleaner with safety socket on the unit. Resources this protection class must be marked with " Class II " ( see right). (VDE 0100 Part 410, 412.2.1.1 ) The contact current must be below 0.25 mA lie (which is indeed noticeable, but harmless ).

Protection class III / low voltage protection

Devices of safety class III work with safety extra-low voltage ( SELV / PELV) and need for mains operation also reinforced or double insulation between mains circuits and the output voltage.

Equipment, extra low voltage ( SELV / PELV), ie voltages not exceeding 50 V ac or 120 V dc voltage from the mains voltage produce, require a safety transformer according to DIN VDE 0570-2-6 and EN 61558-2-6.

From batteries or accumulators, removed protective low voltages designed in protection class III, satisfy without further action.