The complete circuit of a three phase appliance protector is described here. It requires three-phase supply, three 12V relays and a timer IC NE555 along with 230V coil contactor having four poles.
Relays RL1 and RL2 act as sensing devices for phases Y and B, respectively. These relays are connected such that each acts as an enabling device for the subsequent relay. Therefore the combination of the relays forms a logical AND gate connected serially.
The availability of phase R energizes relay RL1 and its normally opened(N/O) contacts close to connect phase Y to the input of transformer X2. The availability of phase Y energizes relay RL2 and its N/O contacts close to connect phase B to…show more content… Here the contact current rating of the four-pole contactor is up to 15A. The availability of phases R, Y and B is monitored by appropriate LEDs connected across the secondary windings of transformers X1, X2 and X3, respectively.
When coil of contactor gets triggered it connects the three-phase supply to the load. When any one or two phase gets failure in three phase supply then this circuit fails in above operation. As the circuit fails in operation 4-Pole contactor RL4 automatically disconnects the three-phase supply to load. By disconnecting thr three phase supply we can protect three phase induction motor or any type of three phase appliance.
FIG 5.1 CIRCUIT DIAGRAM FOR SINGLE PHASING PROTCTION (31)
COMPONENTS
The following are the components required to develop the three-phase appliance protection circuit:-
1.) Resistance (4)
• 3.3K(R1,R2,R3)tolerance-10%
• 4.7K(R4)tolerance-10%
2.) Variable Resistance (1)
• 1M POT
3.) L.E.D (3)
• Red
• Yellow
• Blue
4.) Step down transformer (3)
• Primary-230V
• Secondary-0-12V
• 300mA
• Manufacturer-Beco(2)&Som(1)
5.) Relay (3)
• Series-K-1031
•…show more content… These faults is generally a chronic problem aggravated by a number of factors in the distribution system. Single phasing problem is occurs when any one phase of the three phase supply is not present and huge current will pass through the remaining two phases. So this single phasing and under-over voltage protection is mainly required to ensure that all the various power supplies are operating within their specification. This protection device can act correctly and clear the fault as soon as possible when single phasing, ground or inter phase fault occurs in the supply system. This will protect the system from damaged and supply the power uninterrupted to the
