Question { OPS, 13065 }

why in three phase 440 circuit in all phase current is
almost equal L1-35 A,L2-34 A ,L3-31 A but in nutral when i
check with clamp meter it shows 25 A?

Answer

1)your point of measuring to conder again

2)check whether nutral joint is given to another load which
you not considering for this load

Question { 6156 }

magnetic circuit consume energy

Answer

Magnetic circuit consumes energy not only because of
losses . example for no load transformer is quit ok but we
know motors, which rotate on no load as well as on load .
to develop flux to creat torque it draws current .

Question { ABB, 10585 }

What makes the difference between 50Hz supply and 60Hz
supply which one is economical? What is the use of using
increased frequency?

Answer

50 HZ is uswed in india and also majority in other world.
some of countries uses 60 HZ as UK . The frequency is
inversly proportional to current ,so when drops current
increases or vise versa.the change of frequency is uses in
VFD to change speed .

Question { Siemens, 6613 }

Pls explain about vfd control?Where it is used, Give some
example?

Answer

Variable frequency Drives(vfd) are used for controlling the
speed of AC motors by changing the frequency of power
supply. the advantage of using them is fast and accurate
and more controlled and relaible device they can be used
for where speed is very important such as CNC ,machin
tools , special purpose conveyer m/c etc.

Question { Bajaj, 27158 }

How to Convert horsepower to kva?
what is the three phase formula?
explain me if u can Example..i have 50Hp Moter how can i
convert in kva tell me formula three phases

Rehan Smileavail@msn.com

Answer

1 L.Current xL.Volts x1.732 = KVA =
KW = HPX746
1000 PF
1000XEfficiencyxPF

2 L.Current xL.Volts x1.732XEfficiencyXPF =
KVAX1000XEfficiencyXPF = KWx 1000
xEfficiency = HP

746 746 746



When KVA know When KW know
When HP know
3 L.Current = KVAX1000 = KWx
1000 = HPX746

L.VoltsX1.732
L.VoltsX1.732XPF
LVoltageX1.732XEfficiencyXPF

Question { 5528 }

can we check the resistance of earthing electrode while it
is connected with the neutral of UPS system

Answer

now days simple measuring instrument are availsble eg:-
meco i have seen catloge by which without connecting to
Eatrh Electrode we can measure leackage current as well as
resistance of Earth point/Electrod.

Question { DRDO, 62779 }

two bolbs of 100w and 40w respectively connected in series
across a 230v supply.which bolb will glow bright and why?

Answer

40watt bulb will be very bright ,
The reason 40 watts bulbs have more resistace and
inductance so more voltage drop in series-- more brightes
it.