Question { 6221 }

what's meanning of 1250KVA and how to calculate with
Volttage and Current. answer give with example.

Answer

This is really a basic electrical question but anyway,

Power is measured in Watts and the symbol for power is "P"
and for watts "W"

The formula to calculate Power is Volts X Amps

So this can also be written in short as P = V X A

Since as you have learned in basic mathematics that if there
is no sign between two symbols that means multiply,
so the above can also be written as P = VA and the answer
will be in Watts.

The electrical people have different ways to refer to Power
but it is all exactly the same thing.

They could either call it 1250KVA or say it out fully like
1250KiloWatts(KW), since as above VA = W.

KVA = Kilo (Volts X Amps) = Kilo (Watts)

also

1000Watts = 1 Kilo Watt

Good luck

Question { 6221 }

what's meanning of 1250KVA and how to calculate with
Volttage and Current. answer give with example.

Answer

It might be better in the future to ask electrical questions
in the electrical section, rather that trying to find
someone in instrumentation that can give you answers on
electrical problems you are struggling to understand.

Here's what you need anyway,

Since watts is volts times amps, what is VA?
VA (or volt-amps) is also volts times amps, the concept
however has been extended to AC power.

For DC current:
VA = Watts (DC current).

In AC if the volts and amps are in phase (for example a
resistive load) then the equation is also:
VA = Watts (resistive load)

where V is the RMS voltage and A the RMS amperage.

In AC the volts and amps are not always in phase (meaning
that the peak of the voltage curve is does not happen at the
peak of the current curve). So in AC, if the volts and amps
are not precisely in phase you have to calculate the watts
by multiplying the volts times the amps at each moment in
time and take the average over time.

The ratio between the VA (i.e. rms volts time rms amps) and
Watts is called the power factor PF.

VA•PF = Watts (any load, including inductive loads)
In other words, volt-amps x power factor = watts.
Similarly, KVA*PF = KW,
Or kilovolt-amps times power factor equals kilowatts.

When you want to know how much the electricity is costing
you, you use watts. When you are specifying equipment loads,
fuses, and wiring sizes you use the VA, or the rms voltage
and rms amperage. This is because VA considers the peak of
both current and voltage, without taking into account if
they happen at the same time or not.

Finding the Power Factor:
How do you find the power factor? This isn’t easy. For
computer power supplies and other supplies that are power
factor corrected, the power factor is usually over 90%. For
high power motors under heavy load the power factor can be
as low as 35%. Industry standard rule-of-thumb is that you
plan for a power factor of 60%, which somebody came up with
as a kind of average power factor.

Converting VA to Amps:
How to convert VA to amps? Use the following formula:
A = (VA*PF)/V
Where A stands for the RMS amps, VA stands for volt-amps, V
stands for RMS volts and PF stands for the power factor.

Converting VA to Volts
How to convert VA to volts? Use the following formula:
V = (VA*PF)/A
Where V stands for RMS volts, A stands for the RMS amps, VA
stands for volt-amps, and PF stands for the power factor.

What is KVA?
KVA is just kilovolt-amps, or volts times amps divided by 1000:
KVA•PF = KW (any load, including inductive loads)
Where KVA stands for kilovolt-amps, KW stands for kilowatts,
and PF stands for the power factor.

Keep the factor of 1000 straight when dealing with mixed units:
KVA•PF = W/1000 (any load, including inductive loads)
VA•PF = 1000•KW (Kilowatts to VA)

The Following equations can be used to convert between amps,
volts, and VA.

Converting VA to Amps (voltage fixed)
The conversion of VA to Amps is governed by the equation:
Amps = VA•PF/Volts)
For example 12 VA•0.6/(12 volts) = 0.6 amp

Converting KVA to KW (Kilovolt-amps to Kilowatts)
The conversion of KVA to KW is governed by the equation:
KVA = KW/PF)
For example, if the power factor is 0.6
120 KVA•0.6 = 72 Kilowatts

Converting Watts to KVA (watts to kilovolt-amps)
The conversion of W to KVA is governed by the equation:
KVA=W/(1000*PF)
For example 1500W/(1000*0.83) = 1.8 kVA (assuming a power
factor of 0.83)

Converting Amps to VA (voltage fixed)
The conversion of Amps to VA is governed by the equation:
VA = Amps • Volts/PF
For example 1 amp * 110 volts/0.6 = 183 VA

Converting Amps to KVA (voltage fixed)
The conversion of Amps to KVA is governed by the equation:
KVA = Amps • Volts/(1000•PF)
For example 100 amp * 110 volts/(1000*0.6) = 18.3 KVA

Converting VA to Volts (current fixed)
The conversion of VA to Volts is governed by the equation:
Volts = VA•PF/Amps
For example 100 VA • 0.6/10 amps = 6 volts

Converting Volts to VA (current fixed)
The conversion of Volts to VA is governed by the equation:
VA = Amps • Volts/PF
For example 1.5 amps * 12 volts/0.6 = 30 VA

Converting Volts to Amps at fixed VA
The conversion of Volts to Amps is governed by the equation:
Amps = VA•PF/Volts
For example 120 VA* 0.6 /110 volts = 0.65 amps

Converting Amps to Volts at fixed VA
The conversion of Amps to Volts is governed by the equation:
Volts = VA•PF/Amps
For Example, 48 VA • 0.6 / 12 Amps = 2.4 Volts

Explanation
Amps are how many electrons flow past a certain point per
second. Volts is a measure of how much force that each
electron is under. Think of water in a hose. A gallon a
minute (think amps) just dribbles out if it is under low
pressure (think voltage). But if you restrict the end of the
hose, letting the pressure build up, the water can have more
power (like watts), even though it is still only one gallon
a minute. In fact the power can grow enormous as the
pressure builds, to the point that a water knife can cut a
sheet of glass. In the same manner as the voltage is
increased a small amount of current can turn into a lot of
watts.
Good luck and ask the electricians these questions in the
future please.

Question { UPL, 45668 }

what is the difference between mmhg & mmwc?. i want to
calibrate a transmitter in the range of -100 to 300 mmwc.
Which is the reference for calibrate the Tx,if mmwc not
available?. Is it mmhg or mmho2?.

Answer

Hi there,

mmwc (millimeters Water Column or Water Gauge)
mmH2O milimeters water)

Let me explain the pressure value of each since I can see
you have asked the same question earlier as well.

We all know that the gravitational acceleration of the earth
is 9.80665 m/s2 as a accepted standard around the world.
Our pressure system was also derived from this Universal Law
of Gravitation first developed by Sir Isaac Newton.
I think we all heard the story about Newton sitting under an
apple tree, an apple fell on his head, and he suddenly
thought of the Universal Law of Gravitation.
Anyway long story short, memorize the following formula and
you will not ever get confused again about pressures and levels.
1 meter height of any volume of clean water (1mWC) is equal
to 9,81Kpa. That is the true and accurate pressure value of
1meter height of water, regardless if it is in a small
tubing or the swimming pool or the ocean or the measured
height in the vessel you want to do a level calibration on.
a 1 meter height of clean water is always 9,81 Kpa.
Ok I know still a bit confusing.

Due to the above information we can therefore say 1000mm of
Water Column is = to 1000mm Water = 9,81Kpa or
1000mmWC = 1000mmH2O = 9,81Kpa

Now we all know the formula to calculate the calibrated zero
and span of our transmitters,
sg x g x h = Kpa

So for a vessel with a zero to span distance of 1000mm and a
product sg value of 1(clean water) we can do the calculation.
1 x 9,81 x 1 = 9,81Kpa
or if you want to work only in mmH2O,
sg x h = mmH2O
1 x 1000 = 1000mmH2O
So now you can calibrate your transmitter for the above
example for LRV = 0Kpa and URV = 9,81Kpa or if you set the
UOM on the transmitter to mmH20, you can calibrate it for
LRV = 0mmH2O and URV = 1000mmH20.
If the height or the sg value in your application differs
just substitute your values in the formulas and you will be
able to do any level calibration on any PIPED DP transmitter.
Remember these formulas are only for piped DP transmitters
and not for capillary or wet leg applications.

Ok let's move on to:
mmhg (millimeters mercury)

This UOM is normally used the measure vacuum and 1
atmosphere = 760mmHg.
You can also say 0mmHg = -101,3Kpa(a) since 1 atmosphere =
101,3Kpa. The (a) indicates that we are talking about
absolute pressure and not gauge pressure.

If you really want to confuse yourself you can try and
relate what I have said above in the mmH2O example, to mmHg.
You can say that 1000mmH2O = 73,56mmHg.
Forget about mmHg and don't use it, not even when you work
on vacuum applications. Stick to Kpa or PSI or the UOM that
makes sense to you and what you are use to. All the UOM are
very easy to convert to so always first convert the
measurement to units you are familiar with then start your
calculations.
Personally I only work in Kpa and mmH2O and I don't get
confused at all anymore.

So finally if you want to do you calibration as per your
question and you are SURE that the calibration is right, set
you UOM on your transmitter to mmH2O and set the LRV to
-100mmH2O and the URV to 300mmH2O and put it back on line.

If you do not use a SMART transmitter convert your
calibration values to Kpa or PSI and pump your transmitter
up to these values and set the zero and span accordingly.
-100mmwc to 300mmwc is the same as 0 to 400mmwc so if your
transmitter cannot measure in the negative you can set the
calibration for 0 to 400mmwc as well, just make sure the
zero is good at atmospheric presure.

Question { 4672 }

On LPG sphere tank we used LIT for level indication.High
side port is connected to the bottom of the tank while low
side port connected to the top. I would like to know how to
fill the glycerin on its low side with two condensing pot
installed,one from top and the other one for its drain
line.Please I need your expertise...thanks

Answer

Hi there,

This is called a normal wet leg installation. There is no
need to change the HP and LP around when you use a SMART TX.
All SMART Tx can measure in the negative with the same
amount as in the positive. exp: -1600 to +1600mmH2O

Open your manifold vents to atmosphere and do a zero trim,
next close the equalizing valve on the manifold and open HP
line to atmosphere. Fill the LP line until both catch pots
are full and the Glycerin is running out of the top catch
pot into the line going to the top tapping point of the
vessel. At this point let the liquid in the vessel fill the
HP line. Remember to do some draining to make sure there are
no air bubbles. What you need is to have the LP completely
filled with Glycerin and the HP line filled with Vessel
liquid up to the point where the tubing connects to the
vessel(not more). Whatever the transmitter reads now(neg
value)is called an atmospheric zero value(ATM).DO NOT DO A
ZERO TRIM!!
Use this formula to calculate the LRV and the URV

LRV = ATM value + (distance from bottom tapping on the
vessel to 0% point on vessel x the sg of the vessel liquid)
URV = ATM value + (distance from bottom tapping on the
vessel to 100% point on vessel x the sg of the vessel liquid)

LRV and URV UOM must first be in mmH2O if you took these Z/S
measurements in mm. After you install them with the HART you
can change it to whatever UOM you require.