Changeover device to DIN VDE 0108 – Power systems and safety power supply in buildings for public gatherings: [t-head1-pg]

Automatic resetting, the phase-monitor is set to:

Pick-up voltage U_an = 0,95 × U_n
Drop-out voltage U_b = 0,85 × U_an

Function [t-head3]

Main switch Q1 is closed first, followed by main switch Q1.1 (auxiliary supply).

Phase monitor K1 is energized via the main supply and immediately energizes contactor relay K2. Normally closed contact K2/21–22 blocks the circuit. Contactor Q12 (auxiliary supply) and normally open contact K2/13-14 closes the circuit of contactor Q11, which energizes and switches the mains supply on the load. Contactor Q12 is also interlocked against mains supply contactor Q11 via normally closed contact Q11/22-21.