59 equipped with an inverter, this measurement refers to the electrical supply system on the control panel. This finding was missing in the previous report. However, following some recent near accidents, a survey on the specifications of the inverters installed in the control panels was carried out which resulted in the realization that installers had not been informed by the suppliers about the need to install a specific F.M. residual-current device to protect the inverter. By reviewing documents, we found that all inverter manufacturers require type A or type B residual-current protection. Therefore, the electrical power supply system following the condominium meter must guarantee the protection of people from indirect contacts on the metal masses of the condominium through the adoption of an appropriate residual-current protection device made with an efficient ground circuit In Italy, the technical standard of reference for electrical systems is CEI 64-8 and the construction standards of the equipment are as follows: • standard CEI EN 50178 “Electronic equipment for power plants”; • standard CEI EN 62477-1 “Safety requirements for electronic power converters - Part 1: general”: it is up to the manufacturer of a class 1 equipment to indicate in the installation instructions when any residual current protection must be of type A or B. In compliance with this, the manufacturers of the Inverter (VVVF), in their manuals, always indicate which type of residual-current protection switch (RCD) to install. In the specific case of lift control panels, for example, the manual of an inverter in the chapter “System protection in case of inverter failure” states: “If the assembly regulations of your application provide for the installation of residual current devices (RCDs) as upstream protection, this must be chosen according to the DIN - VDE 0100530 standard as follows: Single-phase inverter type A or B; Three-phase inverter type B “. In Italy, the installation standard relating to electrical systems is CEI 64-8 which in TT systems (typically present in condominiums) require the installation of a special switch (RCD) suitable for the powered circuit and correctly coordinated with the ground circuit. Furthermore, we have found that some inverter manufacturers indicate the possibility of installing type A or type B RCDs, others only type B, but none indicate the possibility of using the generic type AC one. 2) A disconnected brake does not prevent the lift from moving: this finding relates to the winch brake test; upon departure of the lift with the brake shoes closed due to the absence of power to the control coils, the lift moves without the control panel receiving any failure signal. The brake test of the aforementioned winch is normally carried out by all the engineers of the notified bodies during the legal checks on lifts equipped with a control panel with inverter. The control test of the correct adjustment of the brake in most cases, for lifts with limited capacity, generates a fault signal to the control panel which goes into overload mode and prevents it from starting. On the other hand, when the range and speed are more important, it is wrong to assume that the brake can keep the winch motor blocked as the braking torque is much lower than the starting torque and therefore the lift moves despite the brake. This is very dangerous as, in the event of a failure, the locked brake would quickly break the linings resulting in the risk of unrestrained cabin movement. 3) The two winch brake shoes are equipped with a single control coil in the presence of the inverter: this refers to the winch which has an old concept brake unit in which the mechanical elements of the brake that contribute to exerting the braking action are single, so in the event of a mechanical failure of the braking system (brake locked on opening) the cabin could lose control with serious risk for users. Introducing this new inspection was necessary following the recently recorded numerous accidents, which led to investigate the causes and to discover that following the installation of the inverter (VVVF) the malfunctioning braking system (long braking) signals are “masked” thus not evident to the user until the moment of the accident. In many cases blocking the reel in opening made the brake unit cause uncontrolled cabin movement with open doors hitting the head of the shaft (causing injury to the passengers), leaving the landing door open to the void at the landing of the stairs: creating an extremely dangerous situation that leads to extremely serious risk. Consequently, it is necessary to install a braking system that can make the two shoes that open / close the brake independent, as new facilities have been implementing for decades (see UNI EN 81-1 art. 12.4.2.1). 4) The above two conditions of the winch brake have been ad-
RkJQdWJsaXNoZXIy NDUyNTU=