DSH 558/06 Extra safety circuit equivalent to SELV or double/reinforced insulati

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DSH 558/06 0 m+ d" I- n2 `6 v 9 f- _& Q# c$ B/ B: Q. |; r

Extra safety circuit equivalent to SELV or double/reinforced insulation 9 o4 M; r+ |% a

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60570(ed.4) ) o# A/ C; u) ~& c" ~: G% |! J; T4 |

Question:
A client wants to combine a 230 V track system (according to IEC 60570) with a bus-track system, which tracks are accessible. Consequently the bus-tracks may be supplied by a SELV source only, or connected to circuits, which are insulated from live parts by double or reinforced insulation. Due to the fact that both DALI systems (or similar systems) and control systems of electronic ballasts do not comply with the requirements of double insulation, our client created an additional safety circuit between the bustrack and DALI system/electronic ballast. The extra safety circuit consists of six zener diodes (>50 V) and four fuses (250 mA). The diodes guard the system to voltage higher than 50 V and the fuses protect the system against high currents. In this way SELV conditions are guaranteed.
Decision:
# u/ F* a- ^1 H: Z6 N In principle the SELV condition can be reached by electronic means at least according to the standards IEC 60364-4-41 and IEC 61140.
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