kwh and kvarh
Electrician
I somwhow realised there are two meters at my main switchboard.
Kindly advise what are they for and hoe they affect our daily
electricity consumption?
Mark Kinsler
kwh is kilo watt hours: real power multiplied by time, which means that
it represents the energy actually delivered to the load.
kvarh is kilo volt amperes reactive hours, which is "reactive" power
multiplied by time. The units are the same as those of energy, but this
meter does not represent energy delivered to the load because the
measurements are based on those components of current and voltage which
are ninety degrees out of phase.
By comparing the kva and kvarh readings, one can determine the average
power factor of the load. Large kvarh readings would imply that either
large transformer and motor magnetizing currents were demanded or,
conversely, that the system has too great a capacitive component. This
last situation occurs in systems with long runs of cable.
That's the best I can do. Corrections and amplifications are invited.
M Kinsler
--
............................................................................
114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059
Home of the "How Things Work" engineering education program.
See http://www.frognet.net/~kinsler
Andrew Gibb
<Electrician> wrote in message news:395230e0...@news.tm.net.my...
zammy
or even a technician, but he probably can string wires and fulfill the
needs of almost all jobs. why don't you help him instead of using your
vastly superior knowledge to put him down?
again, is there any really stupid question?
not in my opinion.
i work regularly with mill electricians who don't understand power
factor and such but they do a damn fine job of keeping the mills
running.
best wishes, sam
--
honda gyro, diesel powered bmw r100-rt. dodge D-350 cummins, subaru,
maserati biturbo, fiat osca, mercury capri, dodge caravan, case 1816
gold wing.
Andrew Gibb
went on the attack. Chill out.
"Electrician" ..it wasn't a put down...no offence intended.
KVA = SQRT (KW^2+KVAR^2) more commonly expressed
S = SQRT (P^2 + Q^2)
draw a right angle triangle, place S (apparent power KVA) on the hypotenus,
P (real power KW) on the base line or X axis, Q (reactive power KVAR) on the
quadrature axis or the Y axis and from this you can derive all the
relationships bewteen S, P and Q. Cosine of the angle between S and P is
the power factor.
Ideally you try to keep the power fator as close to unity as possible - the
KVAR is not useful to the end user however the utility company still needs
to generate this power - it makes up part of the system KVA. Not sure what
tariff scheme you are on but where I am we are charged for KW useage and a
penalty is imposed if we drop below a 0.8 power factor.
Lightly loaded induction motors are generally the biggest contributor to
poor power factor.
Sam - suggest you train you electricians better - they should understand pf
issues.
Run with it.......
Andrew.
zammy <za...@sgi.net> wrote in message news:3954BE...@sgi.net...
zammy
i really can't spend too much time training. the men are workers of my
clients. i'm just in for a troubleshooting stint and then gone. i do
recognize their good qualities, though.
my best, sam
Mark Daniels
<ag...@ozemail.com.au> writes
>Good point Sam.....bad week I guess. I notice you didnt answer either...just
>went on the attack. Chill out.
>
>"Electrician" ..it wasn't a put down...no offence intended.
>
>KVA = SQRT (KW^2+KVAR^2) more commonly expressed
> S = SQRT (P^2 + Q^2)
>
>draw a right angle triangle, place S (apparent power KVA) on the hypotenus,
>P (real power KW) on the base line or X axis, Q (reactive power KVAR) on the
>quadrature axis or the Y axis and from this you can derive all the
>relationships bewteen S, P and Q. Cosine of the angle between S and P is
>the power factor.
Yep. Good so far.
>
>Ideally you try to keep the power fator as close to unity as possible - the
>KVAR is not useful to the end user however the utility company still needs
>to generate this power - it makes up part of the system KVA. Not sure what
>tariff scheme you are on but where I am we are charged for KW useage and a
>penalty is imposed if we drop below a 0.8 power factor.
The utility company does not generate the kVAR as power. kVA determines
the size of things like the alternator, transfomers and power lines used
to generate and deliver the kVA to the end user. The mechanical drive to
the alternator, comprising steam turbine, diesel engine, shafts,
couplings, belt drives or whatever only have to be sized to handle the
ACTUAL REAL POWER. kVAR is not felt by anything mechanical which may be
driving the generator. Only the actual alternator and all power
transmission equipment attached to it feel the kVAR.
>
>Lightly loaded induction motors are generally the biggest contributor to
>poor power factor.
That is certainly a large part of it. But don't forget such things as
switch mode power supplies in computers.
>
>Sam - suggest you train you electricians better - they should understand pf
>issues.
>
>Run with it.......
>
>Andrew.
>
>zammy <za...@sgi.net> wrote in message news:3954BE...@sgi.net...
>> BUT, i think that he gets points for asking. he may not be an engineer
>> or even a technician, but he probably can string wires and fulfill the
>> needs of almost all jobs. why don't you help him instead of using your
>> vastly superior knowledge to put him down?
>> again, is there any really stupid question?
>> not in my opinion.
>> i work regularly with mill electricians who don't understand power
>> factor and such but they do a damn fine job of keeping the mills
>> running.
>> best wishes, sam
>>
>>
>>
>>
>> Andrew Gibb wrote:
>> >
>> > I dont think you are an electrican if you need to ask this............
>> >
>> > <Electrician> wrote in message news:395230e0...@news.tm.net.my...
>> > > Can someone please tell me the difference between these two readings.
>> > > I somwhow realised there are two meters at my main switchboard.
>> > >
>> > > Kindly advise what are they for and hoe they affect our daily
>> > > electricity consumption?
>>
>> --
>> honda gyro, diesel powered bmw r100-rt. dodge D-350 cummins, subaru,
>> maserati biturbo, fiat osca, mercury capri, dodge caravan, case 1816
>> gold wing.
>
>
--
Mark Daniels
scot...@my-deja.com
the connected loads consume [this is what you pay for].
KVAR = Kilo-Volt Amperes, Reactive [the unit per hour is KVARH]. This is
a meter to find out how bad the power factor is of the connected loads,
which is charged to the user as a penalty for excessively low power
factor [nominal, or 50% and lower].
It figures the total KVA [Kilo-Volt Amperes] of a load, then deducts the
KW from it, which leaves the KVAR [reactive power] If the reactive power
is like 50% of the wattage, then the power company surcharges the user
for excessive KVAR or low power factor.
If you want a more indepth explainaton, contact me direct by E-Mail at:
adst at soca dot com.
Scott Thompson.
In article <395230e0...@news.tm.net.my>,
Electrician wrote:
> Can someone please tell me the difference between these two readings.
> I somwhow realised there are two meters at my main switchboard.
>
> Kindly advise what are they for and hoe they affect our daily
> electricity consumption?
>
Sent via Deja.com http://www.deja.com/
Before you buy.
Chris Pitzel
> I somwhow realised there are two meters at my main switchboard.
KWH is a measure of the amount of energy delivered by your electric
company to the loads on your premises plus the losses in your cabling
and switchgear.
kVArH is a measure of the amount of magnetization energy that was
delivered by your electric company to the loads on your premesis, and
also a measure of how much magnetization energy was returned back to the
electric company's grid.
> Kindly advise what are they for and hoe they affect our daily
> electricity consumption?
Your electric bill likely consists of two major components, one being a
charge for the number of Kilowatt hours (KwH) that you are using, and
another component known as a demand charge.
The bill you receive for KWh represents the fee that the electrical
company charges to burning coal/oil/uranium/etc. in an industrial boiler
or gas turbine to generate the electricity. The demand charge
represents the cost of providing the appropriate generating units,
transformation, switchgear, transmission lines and metering for your
particular installation.
Andrew Gibb
transformer magnetic circuits. The reason the utility wants you to keep the
pf as close to unity as possible is so they dont have to provide it and can
keep their losses as low as possible. KVAR is absorbed by the magnetic
circuits and pf correction looks to add KVAR to the system to compensate.
Someone has to provide it!
SMPS are very small contributors to low pf - note I said in industry.
Thanks for interest.
Mark Daniels <j...@third-millennium.demon.co.uk> wrote in message
news:z$bT1BAvw...@third-millennium.demon.co.uk...
> >> > > Can someone please tell me the difference between these two
readings.
> >> > > I somwhow realised there are two meters at my main switchboard.
> >> > >
> >> > > Kindly advise what are they for and hoe they affect our daily
> >> > > electricity consumption?
> >>
Lim Chiau Wu
> KW from it, which leaves the KVAR [reactive power] If the reactive power
> is like 50% of the wattage, then the power company surcharges the user
> for excessive KVAR or low power factor.
>
> If you want a more indepth explainaton, contact me direct by E-Mail at:
>
> adst at soca dot com.
>
> Scott Thompson.
>
>
> In article <395230e0...@news.tm.net.my
> Electrician wrote:
> > Can someone please tell me the difference between these two readings.
> > I somwhow realised there are two meters at my main switchboard.
> >
> > Kindly advise what are they for and hoe they affect our daily
> > electricity consumption?
> >
>
>
> Before you buy.