It is quite easy to convert kW to amps and amps to kW in a simple 1-phase DC circuit (compared to 3-phase power calculation). This requires only the basic Ohm’s law; You can use our kW to amps calculator here for the conversion.
In 3-phase AC circuits (usually a 3-phase motor), it is not so easy to convert amps to kW and kW to amps. To simplify the whole thing, we’ve created 2 three-step power calculators:
- First 3-phase power calculator converts kW to amps, for this we use 3-phase power formula With 1.732 factor and power factor (we’ll cover the formula as well). You can find a 3-phase kW to amps calculator here.
- Second 3-phase power calculator converts Ampere to kW in much the same way. We apply the classic 3-Phase Motor Current Calculation Formula, You can find here 3-phase amps to kilowatt formula and calculator.
To get an idea of how these calculators work, here’s a screenshot of a 3-phase power calculator:
Before we cover the basics, let’s take a quick example to illustrate that a . how is power calculated 1-Step vs 3-Step the circuit works.
Example: Let’s say we have a 6 kW air conditioner on a 120V circuit. Here’s how many amps it draws:
- Feather 1 step Circuit, 6 kW draw 50 amps,
- Feather 3 phase Circuit (with A.) 1.0 Power Factor), 3-phase power calculator shows that the same 6 kW appliance draws 28.87 amperes,
- Feather 3 phase circuit (with a. 0.6 Power Factor), 3-phase power calculator shows that the same 6 kW appliance draws 48.11 amperes,
To see why we get different amperages on 3-phase circuits, let’s first examine how these amps are calculated using the 3-phase power formula:
3-phase power formula
Here’s the simple formula we use to calculate power on 1-phase DC and AC circuits:
P (kw) , i (amps) × V (Volts) 1,000
Basically, we just multiply the amp by the volt. There is a ‘1,000’ factor to convert W to kW; We want the resulting power to be in kilowatts. 1 kW = 1,000W.
In comparison, the 3-phase power formula is a bit more complicated. Here is the 3-phase power equation:
P (kw) ,i (amps) × V (Volts) × pF × 1.732) 1,000
As we can see, the electrical power in a 3-phase AC circuit depends on:
- i (amps), Electric current, is measured in amperes. The more amps we have, the more power we have in a three-phase circuit.
- V (Volts), electrical potential, is measured in volts. The more volts we have, the more power we have in a three-phase circuit.
- PF, power element, it is a number between -1 and 1 (in practice 0 and 1). power element Defined as the ratio between real power and direct power. If current and voltage are in phase, the power factor is 1. In 3-phase circuits, current and voltage are not in phase; Thus the power factor will be anywhere between 0 and 1. This accounts for the actual/apparent power ratio and is sometimes expressed as rms current. The higher the pF, the higher the kW in the 3-phase circuit.
- 1.732 factor: It is a constant in 3-phase power calculations. It comes from the derivation of this equation. To be precise, we get the square root of 3 (√3).
- 1,000 factors: This is another constant. It converts watts to kilowatts because we usually prefer to deal with kilowatts instead of W.
Because we need to use the power factor to calculate kW from amps, this formula is also known as the ‘3-phase power factor formula’.
We can use this equation to design the first calculator: 3-Step Power Calculator (see below).
Note: Later on, we will also see how we can use the 3-phase current formula to design a 3-phase motor amps calculator. He converts kW to amps in 3-phase circuits, which is very important in electric motor design.
3-Phase Power Calculator: Amps to KW (1st Calculator)
You can freely use this calculator to convert amps to kW in 3-phase circuits. You need to input amps, voltage, and power factor (it’s between 0 and 1, specific to each circuit):
As you can see, the more amps and volts you have, the more powerful 3-phase electric motor you will have. Similarly, a higher power factor is proportional to a higher power output.
You can use this example to see how the 3-Step Power Calculator works: A 100 amps a . motor on 240V 3-phase circuit with a 0.9 power factor Produces 37.41 kW of electrical power. Put these 3 quantities into the calculator, and you should get the same result.
Now for the 3-phase motor current calculation formula:
3-Phase Current Formula
As we have seen, this 3-phase power formula calculates how many kW of electrical power a motor would have given:
P (kw) ,i (amps) × V (Volts) × pF × 1.732) 1,000
To find out how many amperes a motor with a fixed kW power has, we need to rearrange this equation a bit. We get the 3-phase current formula like this:
I (Amps) = P (KW) × 1,000 (V (Volts) × PF × 1.732)
Using this power formula, for example, we can calculate amps to kW a 3-phase motor. Note that if a 3-phase motor with lower voltage and lower power factor will draw more amps to produce the same power output.
Here’s a calculator based on the 3-phase current formula:
3-Phase Motor Amps Calculation: kW to Amps (second calculator)
To calculate kW to amps, you need to input the 3-phase motor’s kW, voltage and power factor. The calculator will dynamically calculate the current (amps) based on your inputs:
You can use this example to check if you are using the 3-phase current calculator correctly: Let’s say we have a 200 kw motor Feather 480V 3-phase circuit with a 0.8 power factor, Such a motor has a draw of 300.70 amps. You can put these numbers in the calculator and see if you get the correct result.
Overall, we hope that these calculators will help you determine the power and current specifications of electric motors. If you have any questions, you can use the comments below and we will try to help you.