the current rating of the fuse must be equal to the load
because the fuses melting point disconnect the circuit if
the current load becomes greater than the specific rating.
in high ruputer capacity fuse,the fuse able to carry1.2
over the rating.meaning 20% more.MCB rating calculation is
to know how mush the consuption load and according to that
cal.we decide the rate of MCB from the catalog rating of
CB, must be more than the load.DONT FORGET THE SHORT
CIRCUIT CALCULATION
depending on the full load capacity ratings is calculated.
It is not necessary to connect MCB and fuse both,one is
enough.if u want to connect both then first fuse the MCB
Under no load condition it is 20% of rated current of the
device.And in full load condition it is 120% of rated
current.For eg., consider the rated current of a motor is
19ampere.then under no load it is 20% of 19 =3.8ampere
=5amp(approx).for full load it is 120%of 19 = 22.8ampere=20
ampere(approx).
Dear all there are two parameters for determining the
selection of MCB
1.Type of load-
Resistive(e.g Home circuits)-B curve MCB(operates @
3-5 times the rated current)
Inductive-Motors etc.-C curve MCB(operates @ 5-10
times the rated current)
Highly inductive load-Transformers etc.-D curve MCB
(operates @ 10-15 times the rated current)
2.current in the circuit.
Now you will find that curve along with rated current is
mentioned on the MCB e.g. C6(do not confuse rated current
with the breaking capacity which is the max. current CB can
witstand)
C6 means this MCB is usable for Inductive load where
Circuit can witstand upto 30 Amps and MCB should trip if
Current Reaches 30 amps(5times of 6Amps)-60 Amps(10 Times)
Rated current is mentioned as 'ln' in electrical literature.
i am using star-delta connections with reverse/forward
direction motion of the 75hp induction motor.What should be
the ratings of Main,Delta and Star contactors and why?
* Signal transmission in sky wave propagation is due to ?
a) Reforction of wave
b) Reflection of wave
c) Pierus through Inosphere
d) None
and Reason for this is????