Electrical Interlock- It is the interlocking of two
incoming power supply by using electrical equipments like
Consider we have two power supply viz, EB and DG supply.If
EB supply cut,DG will run and viceversa.By mistake whether
both EB and DG supply is ON, it will make hazardous action
to our panels.At that time that relay will sense and make
NO,NC changes and allow only one supply pass through our
Mechanical Interlock- It is the interlock between two power
supply by using Key System.
There are two locks and one key. If we want to switch ON EB
power, first we have to lock DG power and remove the key
from DG lock and then we can switch ON EB supply and
Electrical and Mechanical Interlock are used when there two
or more source of power supply to a common load.
For example a Power Utility Electric supply and a standby
Generator power supply. Of course we do not want this two
supply to be connected to the load, not unless properly
synchronize, as the smaller Power supply will get motorize
and eventually be burnt. Usually in the case of smaller size
of Standby generator which is being normally protected by a
electrical and mechanical interlocking device.
Electrical interlocking device like (ACB) Air Circuit or
Breaker and Mechanical Interlocking device is a mechanical
way, bolt or metal strips, design so as not to switch on the
two ACB power supply source at the same time. You can only
switch on one breaker at a time. This will avoid the
Electrical Fault cause by two power source simultaneously
supplying common load.
The safest way is to use both Electrical and Mechanical
interlock on multi source op power supply.
Electrical Interlock :
this interlock is possible only when any
supply is possible by using one shunt trip & Auxiliary
Contact for any two incomers.if two supply EB & DG in normal
condition only normal incomer supply is in on condition.when
Normal supply is cut then dg supply incomer is comes to on
condition so when suddenly Normal supply is come then only
supply available in one incomer other incomer will on the
OFF position itself by using of shunt trip.
Mechanical Interlocking :
this interlock is used by manually
using the castell lock.
Electrical Interlock means=Suppose you have 3 breakers EB
DG and Bus coupler breaker(not only breaker ,MCCB and
contactors also)in that condition only one source should On
i.e either EB and Buscoupler or DG and buscoupler so for
this we are using NO And NC contacts in series with closing
circuit ie in EB clsoing circuit DG NC contacts are using
so that if DG breaker ON the contacts wil open and doesnot
allow voltages to EB closing ckt same for DG circuit.
Mechanical Interlock= Means mechanical locks provided with
three locks and two keys system so that any one source can
clsoe at a time
ELECTRICAL INTERLOCK MEANS a circuit is wired such that only
if the electrical conditions are met it will function.For
example you have electrical locks you can wire your main door and the main gate such
that the main door can only be opened if the gate is closed
and the gate can only be opened if the main door is closed.
So you cannot leave the house without closing the door or
you cannot go into the house without closing the gate.
MECHANICAL interlock the above functions are done
mechanically for example by having a lock each but
having only one key for both, that too you must lock first
in order to remove the key.
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