Before including a lighting device into an electricity grid network and make it interactive, you need to ascertain it is safe. How can you test the safety of a lighting device? How can you make sure it was designed and made in compliance with legal standards?
Now let’s have a look, step by step, at the principal tests and checks which a lighting device has to be subjected to in order to obtain an IMQ certification.
The reference standard is CEI EN 60598-1 “Lighting devices. Part 1: General regulations”.
So let us see what happens in the laboratory. First of all, the technicians control the label and the imprint which should show all the information required by the regulations protecting consumers: name or brand of the manufacturer, reference type, rated voltage, rated power in watt, class insulation and other elements concerning, for example, a correct installation. All this information should be reported clearly and indelibly. During this first phase, they also verify the effectiveness of the instructions for a proper operation of the device. Besides, they inspect all the components one by one once they have been previously certified so as to meet all the related standards: cables, lamp holder, connection devices, plugs, switches, ballast, etc. So far the treatment reserved to our appliance has been, after all, quite simple and “gentle” since it was just a visual test. The hard job begins now with the mechanical resistance test on all the screws. This test is performed with the help of a dynamometric screwdriver. After putting in the electrical terminal a rigid copper conductor of the widest section allowed, the screws are tightened and loosened for five times with a torque of 0.5 Nm for the screws of 3mm of diameter. In case of larger diameters, the twisting moment is to be increased accordingly. Thanks to a special test hammer, technicians prove the mechanical resistance of glasses, caps and other protective parts. The collision energy produced by the hammer on the fragile parts (glass) of a fixed device is 0.2 Nm, while on the other parts is 0.35 Nm.
Children for the love of it and adults by mistake tend to touch everything out of curiosity, even the most hidden parts. That is why the protections against electrical shocks are thoroughly verified and double-checked. Using a specific test finger connected to an electrical network detecting the contacts, technicians make sure that the parts exposed to voltage cannot be touched in any way even if you want to. As far as concerns I class devices, they prove the uninterruptible power of ground circuits. In other words, they verify that the metal parts – exposed for example when the device is open during the replacement of a bulb or the cleaning operations – are connected in a permanent safe way to a terminal or to ground to prevent user contact with dangerous voltage, if electrical insulation fails. The compliance with the regulatory rules is performed through a visual examination by allowing a flux of current (of at least 10 A and fed by a source not higher than 12 V) to run between the terminal or the ground contact and each of the metal parts accessible. Then they measure the voltage drop between the terminal or the ground contact and the accessible metal part; the resistance is calculated considering current and voltage drop. In any case can not be higher than 0,5Ω.
The tests go on. The insulation resistance with a voltage of 500 V in C.C is now controlled.
Here the results obtained must not be lower than those specified by regulations. For example, the value of the insulation resistance measured between the parts carrying current and the metal parts of a II class device should not be lower than 2MΩ. Then a dielectric rigidity test is performed, which is a very useful test because, like the previous test, helps to verify the electric safety thus preventing electric shocks. Among the various parts, different voltage values are employed depending on the type of device. In case of a II class device, for instance, technicians use 1500 V in C.A. between the parts under voltage of different polarity, while they may use up to 3,750 V between the parts under voltage and the parts accessible to users.
The lighting appliances that you can also use outdoor, are subjected to a frightening shower! This must prove the effective protection against any liquid. In fact, as many as forty nozzles fixed on a rotating arch heavily pour on the lit device several litres of water for 20 minutes nonstop. Of course, the examination is successfully passed providing that at the end of such a deluge not a single drop of water is penetrated into the shell of the device.
And here is another important test to verify the protection against dust: the device is this time hermetically sealed and then submitted to a “storm” of talcum powder for 180 minutes. If this very thin powder does not enter the casing, then the test is passed. Another important test, which is practically linked to the two previous ones, is the endurance test. The device is kept in a room at 35° for 168 hours including seven consecutive cycles of 24 hours. During each cycle, it is kept switched on for 21 hours and then switched off for the remaining 3 hours. At the end of this exhausting performance, our appliance must prove efficient and safe as before.
Now it is the turn of another check: the heating test. The device is fed with a voltage producing 1,05 times the rated power of this trial lamp (if incandescent lamps are considered) and as the device reaches a thermic stabilization (this happens after 3 to 4 hours) temperatures are measured in different points. These temperatures, however, should not be higher than the safety levels suggested.
Finally, the device is subjected to the heat and fire tests. The parts in insulating material that supply protection against electric shocks are placed in an oven at the lowest temperature of 125°. On the surface of the trial part is then pressed, with a strength of 20N, a 5mm-wide iron ball, which is eventually removed after an hour. Then the trial part is cooled down for 10 seconds in cold water. If the imprint left by the ball is not larger than 2mm then the part has proved to be resistant to heat and the test is passed successfully. Now the parts in insulating material that keep the parts exposed to voltage must demonstrate to be resistant to flames. A sample of these parts is exposed for 10 seconds to the flames in the point where the highest temperatures are more likely to develop. The test is passed if the combustion does not last more than 30 seconds after the flames have been removed.
As we have already mentioned, the tests we have illustrated above are only some of the 200 tests, verifications and checks that are required by standards. They involve a great deal of accuracy, skills and teamwork, besides at least 15 working days to carry out. This proves how essential is the top-level guarantee provided by an IMQ certification: the certainty of being safe.