Setahu saya, kalau sekering nya atau MCB nya 4 amper, berarti daya yang bisa
digunakan adalah 4 x 220 = 880 VA dan di bulatkan menjadi 900 VA.
Jadi untuk yang 6 amper, daya yang bisa digunakan adalah 1320 VA dan dibulatkan
menjadi 1300 VA.
Kalau beban yang dipasang adalah beban yang bersifat resistif, seperti setrika
listrik, pemanas air, rice cooker, maka nilai VAnya sama dengan nilai Watt.
Namun, kalau bebannya yang dipasang, bersifat induktif, seperti pompa air, AC,
kulkas, bor listrik, maka nilai VAnya tidak sama dengan nilai Watt. Dalam
perhitungan, perbedaannya di definisikan dengan faktor yang disebut sebagai cos
phi.
Demikian juga dengan kalau beban yang dipasang, bersifat kapasitif.
Perbedaan, disebabkan karena bentuk gelombang, kalau di"lihat", antara arus dan
tegangannya, saat di bebani, tidak berimpit atau sefasa dengan bentuk gelombang
tegangan, bisa arusnya lebih dahulu, bisa juga lebih belakang.
Karenanya, banyak dijual alat "penghemat listrik" yang kebanyakan, isinya hanya
berupa capacitor antara sekitar 10uF sampai dengan 47uF yang dipasangkan secara
paralel dengan sumber listrik, dengan tujuan mengkompensasi beban yang bersifat
induktif, menuju menjadi beban resistif. Dengan cara ini, kalau bebannya
banyak yang induktif, terutama AC, maka kalau diukur, arus listrik nya akan
menurun.
Di rumah saya, dengan variasi beban dari berat sampai ringan, kalau menggunakan
capacitor 22uF, bisa antara 3.6% sampai dengan 39.1% dan dengan capacitor 22uF,
bisa antara 4.8% sampai 26.1%. Karenanya saya gunakan yang 47uF, karena bisa
menurunkan sampai 4.8% saat beban penuh.
Nah, untuk rumah tangga, karena yang terpasang adalah KWH meter, bukan KVA
meter, maka alat yang menggunakan capacitor ini, tidak akan menurunkan rekening
listrik tapi hanya menurunkan arus listrik. Dengan menurunkan arus listrik,
maka beban yang bisa dipasang, akan bisa lebih banyak (dan dengan sendirinya,
akan menambah biaya rekening listrik)
Namun untuk industri, pemasangan capacitor ini, akan menurunkan biaya rekening
listrik. Karenanya, di industri tersedia berbagai capacitor bank untuk
digunakan sebagai alat penghemat listri.
Salam.
----- Original Message -----
From: tenly sulistyo
To: ITCENTER@yahoogroups.com
Sent: Tuesday, October 09, 2007 9:19 PM
Subject: Re: Balasan: Re: [ITCENTER] Power Supply <cukup gak?>
salam kenal Jungki mungkin bisa di jelaskan apa yang di maksud cos phi
tersebut, karena jika saya tanya orang pln seperti di bawah ini. untuk
mendapatkan watt.
Listrik di rumah saya 900 watt MCB di depan panel PLN 4 Amp Voltase rumah
saya 220 Volt
900 watt = 220 Volts * 4 Ampere
Listrik di rumah saya 1300 watt MCB di depan panel PLN 6 Amp Voltase rumah
saya 220 Volt
Benar tidak 1300watt = 220 volt x 6 Amp
soalnya kalo saya tanya orang orang listrik di rumah berapa 2200 dan saya
lihat MCB PLN 10 Amp dan voltasenya 220 Volt
Setelah saya hitung 2200watt = 220 v * 10
Jadi
Watt = V x A
Persamaan matematikanya
Watt = VA
Benar tidak ?
Mohon di koreksi jika ada kesalahan.
Terima Kasih
Regards
////////
----------------------------------------------------------///
How Electricity Works
by Marshall Brain
Inside This Article
1. Introduction to How Electricity Works
2. Electricity Basics
3. Generators
4. Electrical Circuits
5. Voltage, Current and Resistance
6. Direct Current vs. Alternating Current
7. Electrical Ground
8. Lots More Information
9. See all Physical Science articles
5.Voltage, Current and Resistance
If you live in the United States, the power outlets in the wall of your
house or apartment are delivering 120 volts.
Imagine that you plug a space heater into a wall outlet. You measure the
amount of current flowing from the wall outlet to the heater, and it is 10
amps. That means that it is a 1,200-watt heater.
Volts * Amps = Watts
... so 120 volts * 10 amps = 1,200 watts.
This is the same for any electrical appliance. If you plug in a toaster and
it draws 5 amps, it is a 600-watt toaster. If you plug in a light and it
draws half an amp, it is a 60-watt light bulb.
Let's say that you turn on the space heater, you go outside and you look at
the power meter. The purpose of the power meter is to measure the amount of
electricity flowing into your house so that the power company can bill you
for it. Let's assume that nothing else in the house is on, so the meter is
measuring only the electricity used by the space heater.
Your space heater is using 1,200 watts. That is 1.2 kilowatts -- a kilowatt
is 1,000 watts. If you leave the space heater on for one hour, you will use
1.2 kilowatt-hours of power. If your power company charges you 10 cents per
kilowatt-hour, then the power company will charge you 12 cents for every
hour that you leave your space heater on.
1.2 kilowatts * 1 hour = 1.2 kilowatt-hours
1.2 kilowatt-hours * 10 cents per kilowatt-hour = 12 cents
Similarly, if you have a 100-watt light and you leave it on for 10 hours,
the light will consume 1 kilowatt-hour (100 watts * 10 hours = 1
kilowatt-hour).
If you have a 20,000-watt heat pump and you leave it on for five hours every
day, you will consume 100 kilowatt-hours per day (20 kilowatts * 5 hours =
100 kilowatt-hours), or 10 dollars of power per day if a kilowatt-hour costs
a dime. If you do that for a month, your heat pump costs you (30 * $10) $300
per month. That is why your electric bills can get so high when the
temperature is very cold -- the heat pump runs a lot.
The three most basic units in electricity are voltage (V), current (I) and
resistance (r). As discussed previously, voltage is measured in volts, and
current is measured in amps. Resistance is measured in ohms.
We can extend the water analogy a bit further to understand resistance. The
voltage is equivalent to the water pressure, the current is equivalent to
the flow rate, and the resistance is like the pipe size.
There is a basic equation in electrical engineering that states how the
three terms relate. It says that the current is equal to the voltage divided
by the resistance.
I = V/r
Let's say you have a tank of pressurized water connected to a hose that you
are using to water the garden. What happens if you increase the pressure in
the tank? You probably can guess that this makes more water come out of the
hose. The same is true of an electrical system: Increasing the voltage will
make more current flow.
Let's say you increase the diameter of the hose and all of the fittings to
the tank. You probably guessed that this also makes more water come out of
the hose. This is like decreasing the resistance in an electrical system,
which increases the current flow.
When you look at a normal incandescent light bulb, you can physically see
this water analogy in action. The filament of a light bulb is an extremely
thin wire. This thin wire resists the flow of electrons. You can calculate
the resistance of the wire with the resistance equation.
Let's say you have a 120-watt light bulb plugged into a wall socket. The
voltage is 120 volts, and a 120-watt bulb has 1 amp flowing through it. You
can calculate the resistance of the filament by rearranging the equation:
r=V/I. So the resistance is 120 ohms. If it is a 60-watt bulb, the
resistance is 240 ohms.
Beyond these core electrical concepts, there is a practical distinction that
happens in the area of current. Some current is direct, and some current is
alternating -- and this is a very important distinction.
/----------------------------------------------------------///
What are amps, watts, volts and ohms?
Inside This Article
1. What are amps, watts, volts and ohms?
2. Electrical Efficiency
3. Lot More Information
4. See all Physical Science Article
The three most basic units in electricity are voltage (*V*), current (*I*,
uppercase "i") and resistance (*r*). Voltage is measured in volts, current
is measured in *amps* and resistance is measured in ohms.
[image: power lines]
Karl Weatherly
*More voltage in an electrical system makes more current flow.*
A neat analogy to help understand these terms is a system of plumbing pipes.
The voltage is equivalent to the water pressure, the current is equivalent
to the flow rate, and the resistance is like the pipe size.
There is a basic equation in electrical engineering that states how the
three terms relate. It says that the current is equal to the voltage divided
by the resistance.
*I = V/r*
Let's see how this relation applies to the plumbing system. Let's say you
have a tank of pressurized water connected to a hose that you are using to
water the garden.
What happens if you increase the pressure in the tank? You probably can
guess that this makes more water come out of the hose. The same is true of
an electrical system: Increasing the voltage will make more current flow.
Let's say you increase the diameter of the hose and all of the fittings to
the tank. You probably guessed that this also makes more water come out of
the hose. This is like decreasing the resistance in an electrical system,
which increases the current flow.
Electrical power is measured in *watts*. In an electrical system power (*P*)
is equal to the voltage multiplied by the current.
*P = VI*
The water analogy still applies. Take a hose and point it at a waterwheel
like the ones that were used to turn grinding stones in watermills. You can
increase the power generated by the waterwheel in two ways. If you increase
the pressure of the water coming out of the hose, it hits the waterwheel
with a lot more force and the wheel turns faster, generating more power. If
you increase the flow rate, the waterwheel turns faster because of the
weight of the extra water hitting it.
On the next page, we'll talk more about electrical efficiency.
///----------------------------------------------------------///
On 10/9/07, berry rida <[EMAIL PROTECTED]> wrote:
>
>
>
> jungkiwenas <[EMAIL PROTECTED] <jungkiwenas%40gmail.com>> wrote: harus
> dikali cos phi baru jadi watt klo hanya arus kali amper baru dapet VA
> klo DC iya bener begitu
> thx
> regads
>
> Masih belum selesai juga ya bahas topik ini....
> apa gak ada tema lain apa yang lbh pnting dari pada
> ini.............aneh!!!!!!!!!!!!!
> forum IT ????????????????
>
> ---------------------------------
> Bergabunglah dengan orang-orang yang berwawasan, di bidang Anda di Yahoo!
> Answers
>
> [Non-text portions of this message have been removed]
>
>
>
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
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