Question { 13530 }

how many percent setting of motor over load relay of its
full load current

Answer

125% of the motor full load current require for Overload relay.

Question { 6699 }

tell me the operation of ELCB. How it detects a fault?

Answer

EARTH LEAKAGE CIRCUIT BREAKER WORKS IF IT GETS ANY CURRENTS
ACROSS EARTHING & IT DETECTS CURRENT THROUGH THIS OPERATION:
WE KNOW THE VECTOR SUM OF THREE PHASES IS EQUAL TO NEUTRAL &
EQUALS TO ZERO.IF EARTH DETECTS ANY CURRENTS THEN THROUGH
NEUTRAL FLOWS SOME AMOUNT OF CURRENT AND THE ELCB TRIPS OUT.

Question { 6699 }

tell me the operation of ELCB. How it detects a fault?

Answer

A voltage-sensing ELCB does not sense fault currents from
live to any other earthed body.so current type ELCB is used.

ELCBs have one advantage over RCDs: they are less sensitive
to fault conditions, and therefore have fewer nuisance
trips. (This does not mean they always do, as practical
performance depends on installation details and the
discrimination enhancing filtering in the ELCB.) Therefore
by electrically separating cable armour from the cable
circuit protective conductor, an ELCB can be arranged to
protect against cable damage only, and not trip on faults in
downline installations.
There are two types of ELCB.One-VOLTAGE operated & Current
Operated.A voltage-operated ELCB detects a rise in potential
between the protected interconnected metal work (equipment
frames, conduits, enclosures).They operate at a detected
potential of around 50 volts to open a main breaker and
isolate the supply from the protected premises.
The earth circuit is modified when an ELCB is used; the
connection to the earth rod is passed through the ELCB by
connecting to its two earth terminals. One terminal goes to
the installation earth CPC (circuit [[Power system
protection |protective]] conductor, aka earth wire), and the
other to the earth rod (or sometimes other type of earth
connection).

Question { TCS, 18844 }

will a fluorescent bulb work when dc is passed through it??
if not why??

Answer

no.because the density of the filament of the fluorescent
lamp is very high for the DC supply.hence DC voltage will
not glow the lamp