safety extra-low voltage: voltage not exceeding 42 V between conductors and between conductors and earth, the no-load voltage not exceeding 50 V When safety extra-low voltage is obtained from the supply mains, it is to be through a safety isolating transformer or a convertor with separate windings, the insulation of which complies with double insulation…
extra-low voltage: voltage supplied from a source within the appliance that does not exceed 50 V between conductors and between conductors and earth when the appliance is supplied at rated voltage According to the definition of the EU Low Voltage Directive, low voltage ranges from 50-1000V for AC and 75-1500V for DC. By the way,…
creepage distance: shortest distance along the surface of insulation between two conductive parts or between a conductive part and the accessible surface. Charges can be propagated in a directional manner through the air, thus forming an current. This is the meaning of clearance. Charges can actually also propagate through the insulating material itself, because no…
clearance: shortest distance in air between two conductive parts or between a conductive part and theaccessible surface. Clearance is a very important concept. In order to understand clearance, we need to say it again that no substance is completely insulated, and air can also conduct electricity. When the voltage is very high, the current will…
class III construction: part of an appliance for which protection against electric shock relies upon safety extra-low voltage and in which voltages higher than those of safety extra-low voltage are not generated.Note basic insulation may be required in addition to supply at SELV. Refer to 8.1.4.NOTE 2 If the main part of the appliance operates…
class III appliance: appliance in which protection against electric shock relies on supply at safety extra-low voltage and in which voltages higher than those of safety extra-low voltage are not generated.NOTE basic insulation may be required in addition to supply at SELV. Refer to 8.1.4. To understand this, you need to first understand what is…
The emphasis here is on a part of the construction on the appliance, which can meet the requirements of double insulation or reinforced insulation. Therefore, a class I appliance will also contain a class II construction .Example: The oven shown in the figure below uses a metal shell and a plastic switch knob. When the…
class II appliance: appliance in which protection against electric shock does not rely on basic insulation only but in which additional safety precautions are provided, such as double insulation or reinforced insulation, there being no provision for protective earthing or reliance upon installation conditions. NOTE 1 Such an appliance may be of one of the…
class I appliance: appliance in which protection against electric shock does not rely on basic insulation only but which includes an additional safety precaution, in that conductive accessible parts are connected to the protective earthing conductor in the fixed wiring of the installation in such a way that conductive accessible parts cannot become live in…
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