11-06-2014, 12:25 PM
Single Phasing Preventer
Single Phasing.docx (Size: 60.63 KB / Downloads: 11)
INTRODUCTION
In a poly polyphase machine like a three-phase induction motor requires three phase power supply.If any of the phases get cut-off due to any error,a fault current produced due unbalancing of three phase supply which causes a harmful effect to the motor windings.
Single phasing preventer is a protective project which prevents the machine from single phasing.It disconnects all the phases whenever any of the phases get cut-off.Three transformers of 12V are connected respectively with the phases R,Y & B with the neutral common.The full wave rectifier circuit with each transformer provides supply for three 12V relays.Relay's pole & N/O terminals are connected in series to each-other with a phase supply(here we use R-phase) to a high capacity three pole relay.This high capacity relay are used to switch three-phase machines.