Question { 5976 }

IN GENERAL PRACTICE HOW KVAR AND CAPACITANCE VALUE OF
CAPACITOR CALCULATED?

Answer

for 3-ph system
Kvar=Sqrt(3)*v*i*sin(phi)
or Kvar=kw*tan(phi)

and for value of capacitance when kw or kvar is known

c=KVAR/(2*3.14*f*v^2) when capacitors are connected in Star

c=KVAR/(6*3.14*f*v^2) when capacitors are connected in Delta

I think the above information is in line with your question

If u want any further details mail me @ raviteja.vaka@gmail.com

Question { 10274 }

tell me about vfd

Answer

The main purpose of VFD is to control the speed of the motor
in general if u take an induction motor its speed can be
changed either by voltage or by frequency if we made voltage
alone variable also speed will change but only up to certain
point on the other hand if speed control is achieved by
frequency speed control is only possible up to certain
limits beyond that the flux will be saturated

The best method is to control the speed by means both
voltage and frequency but keeping their ratio constant

this can be achieved by means of scr (semi controlled
rectifier) vfd is a closed loop system it takes the feedbsck
of speed from the motor (Tacho genrator or Current Fb)and
adjusts the firing of scr accordingly

Now a days in modern technology Converter or inverter
circuit is 6 pulse or 12 pulse depending on the application

Question { Hyundai, 37761 }

What is VCB? Where it is installed?

Answer

VCB stands for Vacuum Circuit Breaker
As the name suggests that the phenomenon of arc quenching will happen in Vacuum medium.
It is generally used in MV applications(3.3-36KV)
The main advantages of VCB being it has high dielectric strength(8 Times higher than air and 4 times higher than SF6) which makes it easier to quench the arc with less gap between the contacts. Also the life of VCB is considerably high owing to less maintenance and ease of Vacuum bottle replacement. Also unlike SF6 it is not a harmful to environment and less dangerous comparative to OIL CB. Generally the pressure maintained in Vacuum chamber is 10^-6 bar.

Regards
Raviteja V

Question { 10799 }

what is the necessity of neutral in 3 phase system?

Answer

In most of the 3-ph systems neutral is provided just take care of the unbalanced current. Unbalanced current is nothing but when any of the phase is slightly overloaded or in case of phase failure in balanced currents will produced to carry these currents safely to earth without disturbing the other phases and other connected equipment to the distribution board neutral is generally provided.

and all the neutrals of the db's (Distribution boards) are interconnected and at the transformer this nuetral will solidly grounded.

Question { 12849 }

We have laid the single core Armoured cable 7 nos ( 2 each
phase & 1 neutral ) to cater our electrical load .
the issue is though we have Glanded the cable both the end
also givan the earthing to the panel both the end we are
facing a heavy sparking at the gland side. what could be
the reason.

Answer

Mr.Virendra i would like to know the details of load means
which kind of load and ur suitability of ur cable with ur load

Question { 4927 }

what will happen if neutal in AC ckt will get open

Answer

Is it 3-Ph or 1-ph if it is single phase the circuit will
get open because the the current has to have a return path.

If it is three phase star network the circuit will get
unbalanced

Question { 5218 }

is the electrical energy photo copy possible or
not???????????? give me some idea about that i m very great
full tu u.

Answer

what do you mean by photo copy of electrical enegy u want to picturise the electrical energy or u want made photo copy of it

Question { 9501 }

how to find the 2500 KVA transformer rated primary and
secondary volt and current?

Answer

It is not possible unless u provide the input voltage u r going to give for the transformer and how much voltage u want as out put

however if u know input & output voltages primary and secondary current values can be calculated as fallows

2500 KVA 33KV/433V

Then primary current=2500/sqrt3*33=43.745A
And Secondary current=2500/sqrt3*0.433=3333.34A

Question { 28666 }

what is mathematical relation between ac to dc current
how will convert Iac=50amp to Idc

Answer

Hello Mr. Osho katyal

How come sine wave expression comes in to picture for a dc current?

Question { 2842 }

How to calculate the value of capacitance of a capacitor
used in power factor improvement plant if we know KVAR and
voltages?

Answer

for 3-ph system
Kvar=Sqrt(3)*v*i*sin(phi)
or Kvar=kw*tan(phi)

and for value of capacitance when kw or kvar is known

c=KVAR/(2*3.14*f*v^2) when capacitors are connected in Star

c=KVAR/(6*3.14*f*v^2) when capacitors are connected in Delta

I think the above information is in line with your question

If u want any further details mail me @ raviteja.vaka@gmail.com

Question { Aarti Steels, 4743 }

how to calculate size of cable from motor current given and
how to calculate full load current of a induction motor.

Answer

First the simple one: IM Full Load Current
I=W/root(3)*V(L-L)*PF*Efficiency of Motor

PF and Efficiency will be available from name plate data of
IM. In general u can consider PF=0.8 and Efficiency=0.85

Ex: FLC of 37 KW motor having 415V, 0.8 pf and efficiency as
0.85

I= 37000/Root(3)*1.732*0.8*0.85
I=75A

For calculating the cable size they are many factors to be
considered
* Load Current
* Voltage Level
* Length
* Voltage Drop
* Temperature Factor
* Grouping Factor

Question { Aarti Steels, 4743 }

how to calculate size of cable from motor current given and
how to calculate full load current of a induction motor.

Answer

For further clarification pl mail me @ raviteja.vaka@gmail.com