The conversion between Watts and Amps is an essential calculation in electrical engineering and has practical applications in many areas, from electrical system design to power system management. Knowing the correct formulas and how to apply them helps ensure the safety and efficiency of electrical systems.
The Watts to Amps calculator we offer helps you calculate the power absorbed by a circuit based on the type and intensity of the electrical current absorbed. In the following text, we will explain the calculation formulas and how they differ between direct current, single-phase alternating current, and three-phase alternating current.
The basics
Electric power is the work done in a unit of time by an electric field on an electric charge: a definition so simple and intuitive that it makes you think that even the formula to calculate it is straightforward. It is, but it is not precisely trivial: there is the fact that the current can be
- direct current;
- alternating current.
The alternating current can be,
- single phase;
- three phases.
But there is more; connecting the wires in a three-phase AC circuit can be
- star-shaped;
- in a triangle.
All these different “types” of current mean various formulas for calculating electrical power and converting between Watts and Amps.
Watts to Amps Calculator
Amps:
How to use the calculator
Once the type of circuit (direct current or single-phase alternating current), the current, the voltage, and—in the case of alternating current circuits—the power factor (a decimal number between 0 and 1 (0.8, for example)) are known, the calculator calculates the power of an electrical circuit.
In practice, that’s enough,
- select the type of circuit;
- enter the voltage value,
- enter the power value,
- enter the form factor (if the circuit is alternating current)
The calculator will calculate the current absorbed by the electrical circuit.
It is advisable to check the results obtained always. And report any errors or malfunctions.
Formulas for calculating Watts to Amperes
The formulas used to calculate the current (Amperes) from the power (Watts) depend on the type of circuit:
DC (Direct Current)
I = P / V
Where:
- I = Current (Amperes)
- P = Power (Watt)
- V = Voltage (Volt)
AC Monofase
I = P / (V * cosφ)
Where:
- I = Current (Amperes)
- P = Power (Watt)
- V = Voltage (Volt)
- cosφ = Power Factor
AC Three Phase (Line Voltage)
I = P / (√3 * VL *cosφ)
Where:
- I = Current (Amperes)
- P = Power (Watt)
- VL = Line Voltage (Volts)
- cosφ = Power Factor
AC Three Phase (Phase Voltage)
I = P / (3 * VP *cosφ)
Where:
- I = Current (Amperes)
- P = Power (Watt)
- VP = Phase Voltage (Volts)
- cosφ = Power Factor
Rapid Watt-Ampere Conversion Table
FAQ
What is power factor?
Power factor (cosφ) is a value between 0 and 1 that indicates how efficiently a load uses electrical energy. A power factor of 1 indicates a purely resistive load (e.g. an incandescent light bulb). Inductive (e.g. motors) or capacitive loads have a power factor less than 1.
What voltage should I use for a three-phase circuit?
It depends on the type of connection. If you know the voltage between two phases (line voltage), use the formula with VL. If you know the voltage between one phase and neutral (phase voltage), use the formula with VP. The line voltage is √3 times the phase voltage.
Can I use this calculator for any device?
Yes, provided you enter the correct values for power, voltage and, for AC circuits, power factor. Consult your device specifications or user manual to obtain these values.
Basics of electrical engineering
For the benefit of those who are not very familiar with electrical circuits, it helps to point out that:
- domestic electrical circuits they work at 220 V (a voltage difference that is considered in electrical engineering low voltage) and I’m a single-phase alternating current that is, circuits powered by a single alternating voltage. The form factor (i.e. the frequency variation) will be closer to unity the more resistive the circuit is (the resistance non determines no phase shift between voltage and current). On the other hand, a capacitive circuit (characterized by an alternating electric current generator and a capacitor connected to each other) will have a form factor tending towards zero.
- than circuits powered by batteries and batteries they have voltages ranging (generally) from 1.2 to 24 Volts and are DC.
- than in industrial electrical circuits and electrical distribution medium and high voltage are used (high voltages make electrical transport over long distances more efficient) and the currents are three-phase alternating.
Practical applications of conversion
The conversion between watts and amperes has numerous practical applications in the field of electrical engineering and electrical engineering. Here are some of the main ones:
Cable sizing
One of the most common applications of the conversion is in the sizing of electrical cables. It is essential to choose cables with an adequate section to avoid overheating and power losses. Knowledge of the current absorbed (in Amperes) helps determine the appropriate size of the cables according to current regulations, such as CEI 64-8 in Italy.
Design of electrical systems
In the design of electrical systems, both residential and industrial, it is crucial to accurately calculate the current to correctly size switches, fuses and other protection devices. For example, an engineer must ensure that the circuit breaker has sufficient current capacity to avoid unwanted disconnection.
Backup power systems
When designing emergency power systems, such as generators and UPS, it is necessary to know the total current required to correctly size the equipment. For example, a UPS that must support a total load of 5 kW at 230 volts must be able to provide a current of:
Photovoltaic systems
In the field of renewable energy, the conversion between Watts and Amperes is essential for correctly sizing the components of a photovoltaic system, including inverters and batteries. For example, knowing how much current a solar panel produces helps to choose the right inverter and correctly size the storage batteries.
Home appliances and electronic devices
For household appliances, such as electric ovens or air conditioners, the conversion is useful for understanding the impact on energy consumption and electricity bills. For example, an air conditioner that consumes 2000 Watts at 230 Volts absorbs approximately 8.7 Amperes, and this figure is crucial to avoid overloading the circuit.
