ATS YEQ2Y63-800A(Integral type) Class PC Intelligent type dual power transfer switch The controller measures the normal (N) and reserve (R) supplies of the two-circuit supply and switches between the both. The default in the initial state is normal power supply. When the normal power supply (N) is abnormal (overvoltage, undervoltage or open-phase for any phase of supply voltage), the normal power supply (N) switches to the critical level after switch-off time delay. Then it switches automatically to the reserve supply (R) after switch-on time delay for the power supply. When the normal power supply (N) returns to normal, it can't restore automatically. 3 Power grid and generation