Normal operation L1 L2 L3 N K1 K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle 5,0A Lx Ly/NIN ~ V Ires M [Nm] 0 0,2 0,4 0,6 0,8 1,0 cos  I [A] nominal load I res OK L2L1L3 M ▼M ▲

Normal operation L1 L2 L3 N K1 K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle 0,86 Lx Ly/NIN ~ V cosφ M [Nm] 0 0,2 0,4 0,6 0,8 1,0 cos  I [A] nominal load I res OK L2L1L3 M ▼M ▲

Underload, e.g. broken belt L1 L2 L3 N K1 K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle cosφ Lx Ly/NIN ~ V M [Nm] 0 0,2 0,4 0,6 0,8 1,0 cos  I [A] underload I res OK L2L1L3 M ▼M ▲

Overload, e.g. blockage L1 L2 L3 N K1 K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V Ires M [Nm] 0 0,2 0,4 0,6 0,8 1,0 cos  I [A] overload I res OK L2L1L3 M ▼M ▲

Cable break L1 L2 L3 N K1K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V current in remaining cables rises to keep up the torque Ires K1K2 OK L2L1L3 M ▼M ▲

Phase failure of L1 L2 L3 N K1 K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V Loss of supply voltage OK L2L1L3 M ▼M ▲

Phase failure of L2 L1 L3 N K1K2 K1K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V cosφ Phase shift of approx. +30° => cos φ rises OK L2L1L3 M ▼M ▲

Phase failure of L3 L1 L2 N K1K2 K1K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V cosφ Phase shift of approx. -30° => cos φ falls OK L2L1L3 M ▼M ▲

Phase sequence L1 L3 L2 N K1K2 K1K2 SIEMENS φ-> cos φ = PF Ires-> Active current onDEL-> Current on delay Mem ?-> Memory? NC -> Circuit principle Lx Ly/NIN ~ V cosφ cos φ becomes (1 - cos φ) OK L2L1L3 M ▼M ▲