Appliances Safety
Glossary - Testing the safety of electrical appliances, machines and switchboards CE Marking
Loop test
It is mandatory that any product sold in the European Union (EU) to have a CE label on it. The CE mark is a conformity mark which proves that a product has met all the health, safe- ty and environmental requirements set out by European Directives in order to ensure that the product is suitable for sale.
Discharge Time
When a high powered appliance or ma-chine is powered up, the in- ductive and capacitive components within the device become charged. When the device is switched off, people usually assume that the power will be immediately dis- charged but this is not always the case.
Inductive and capacitive components can hold their charge (even after the power has been re- moved) which can prove dangerous for anybody who comes in contact with the appliance/machine/switch- gear. The time it takes for an appli- ance to discharge can also change with time due to component deg- radation, impurities and pollution. The discharge time function on the Metrel test instruments measure how long it takes for the device to discharge itself to a safe level of voltage.
Functional Test
The functional test powers up an appliance to check that it works cor- rectly. While doing this, the instru- ment can also measure a variety of different information including volt- age, current, power usage, cos ϕ and power factor.
4. 18 Accessories: page 4.24
In order for a high powered ma- chine or switchgear to discharge correctly and for safety devices to act correctly and within the set time limits, it is important that the impedance of the fault loop (live to earth impedance) that supplies power to the device is adequate and appropriate. A loop test meas- ures the amount of impedance in the wiring that supplies the de- vice. Once measured, this can be compared to fault loop impedance limits set out in the appropriate regulations in order to ensure that the device is safe to use.
Appliance
A device, machine or piece of equip- ment, especially an electrical one that is used in the house, such as a cooker or washing machine.
Machine
A piece of equipment with several moving parts which uses power to do a particular type of work.
Switchgear
A switching/ interrupting device used in connection with generation, trans- mission, distribution and conversion of electric power for controlling, metering protecting and regulating devices.
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