Three Phase Power Calculator

NISAKE GAME

Contains ads

About this app

[Please note first]
This app multiplies and divides the figures you type, and nothing more.
It does not size breakers, cables, feeders, service amperage or distribution
boards, and it gives no advice on shock hazard, safety or installation work.
It does not pick motors, work out starting current, or size correction
capacitors. It holds no power factor figures for particular machines, so you
enter the power factor yourself.

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Φ Three Phase Power Calculator - drop the √3 and you are 42.3% short

Three-phase power carries a factor of √3, about 1.732.
Leave it out and you keep 57.7% of the real figure, which is 42.3% short.

This app puts the three-phase formula and the single-phase one side by side,
so a missing √3 shows itself instead of hiding in the answer.

■ 42.3% is always 42.3%

At 200 V or 400 V, at 20 A or 50 A, the share never moves.
The √3 multiplies the whole thing, so the ratio between the two stays put.
You can check it from the two kVA figures on the screen.

■ Get it backwards and you are 73.2% over

Put a single-phase load through the three-phase formula and it grows by about
1.732 times. Four tenths short and seven tenths over are two faces of one error.
The kVA-to-amps screen shows that side of it.

■ kVA does not care about the power factor

Apparent power in kVA depends only on the volts and the amps.
Multiply by the power factor and you get real power in kW.
200 V and 30 A is 10.3923 kVA, and 8.3138 kW at a power factor of 0.8.
At 0.95 it is 9.8727 kW, at 0.7 it is 7.2746 kW.
Change the power factor as you like and the kVA stays at 10.3923.

■ Two ways in: from amps, or from kVA

"How many amps does this machine draw" and "how many amps does a 10 kVA
machine draw on 200 V" are two different questions.
Both are on the same screen.
10 kVA on 200 V is 28.8675 A on three phases, and 50.0000 A if you use the
single-phase formula.

■ You type the power factor

The power factor differs from machine to machine, and from model to model
within the same duty. There is no sound source for such a table, so the app
does not carry one.

■ What it gives you

Three-phase apparent power (kVA), three-phase real power (kW),
apparent power from the single-phase formula (kVA) and its shortfall (%),
three-phase current (A), current from the single-phase formula (A)
and its excess (%).

■ Good for

▪ Turning the volts and amps of a three-phase machine into kVA and kW
▪ Seeing how many amps a machine rated in kVA draws at a given voltage
▪ Checking whether the √3 went in, by reading both formulas at once

■ Things worth knowing (included in the app)

▪ Without the √3 you keep 57.7% of the real figure, 42.3% short
▪ That share does not change with the voltage or the current
▪ The mistake the other way round is about 1.732 times, 73.2% over
▪ kVA depends on volts and amps alone; the power factor plays no part
▪ 200 V and 30 A is 10.3923 kVA, and 8.3138 kW at a power factor of 0.8
▪ 10 kVA is 28.8675 A on 200 V and 14.4338 A on 400 V
▪ The 10.3923 kVA from 200 V and 30 A comes back as 30.0000 A

■ How the app is built

▪ A single screen and no settings page
▪ Nine common values, each one tap away
▪ Your last five entries are kept and can be tapped to restore
▪ One tap copies the result
▪ Japanese and English, following your device language
▪ No account needed. The calculation runs on your device and the figures you type are never sent anywhere

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Note: this app multiplies and divides the figures you type, and nothing more.
It makes no judgement about breakers, cable sizes, ampacity, feeder design,
service amperage or distribution boards, and gives no advice on shock hazard,
safety or installation work. Motor selection, starting current and correction
capacitor sizing are out of scope, as are split-phase supplies and any
difference due to supply frequency.

What’s new

• An ad now appears when the app starts
• Shorter wait at startup when the app skips the ad, such as on first launch