AC/DC Current Calculator

Calculate single-phase and three-phase currents, convert between power and current, and analyze Wye/Delta configurations.

Watts (W) or Kilowatts (kW)
Line-to-Line Voltage (V)
Decimal value (0 to 1)
Decimal value (0 to 1)

Results

Line Current
0.000 A
Phase Current
0.000 A
Line Voltage
0.0 V
Phase Voltage
0.0 V
Apparent Power
0.0 VA
Reactive Power
0.0 VAR

Formulas Used:

3-Phase: P = √3 × VL × IL × PF × η
Wye: VP = VL/√3, IP = IL

Connection Notes:

  • • Wye: Neutral point, phase voltage = line voltage ÷ √3
  • • Delta: No neutral, phase voltage = line voltage
  • • Line current and phase current relationships vary by connection
  • • Power calculations use line voltage and line current

Understanding AC and DC Current Calculations

Calculating current in DC and AC circuits requires different formulas depending on the circuit configuration. DC circuits use simple Ohm's Law, while AC circuits must account for power factor, phase relationships, and whether the system is single-phase or three-phase. This calculator handles all scenarios accurately.

DC Current Calculation

For DC circuits, current is calculated using:

I=\ racPVI = \ rac{P}{V}
  • I: Current in amperes (A)
  • P: Power in watts (W)
  • V: Voltage in volts (V)
  • Simple relationship - no power factor considerations

Single-Phase AC Current Calculation

For single-phase AC circuits:

I=\ racPV imesPFI = \ rac{P}{V \ imes PF}
  • PF: Power factor (typically 0.8-0.95 for motors)
  • Accounts for phase difference between voltage and current
  • Used in residential and light commercial applications
  • Common voltages: 120V, 240V (North America), 230V (Europe)

Three-Phase AC Current Calculation

For balanced three-phase AC circuits:

I=\ racP3 imesVL imesPFI = \ rac{P}{\sqrt{3} \ imes V_L \ imes PF}
  • 3≈1.732\sqrt{3} \approx 1.732
    : Three-phase factor
  • VLV_{L} Line-to-line voltage
  • Used in industrial and commercial power systems
  • Common voltages: 208V, 480V, 600V (NA), 400V (Europe)

Wye (Star) vs Delta Configurations

Wye (Y) Connection:

  • VL=3 imesVphaseV_L = \sqrt{3} \ imes V_{phase}
  • IL=IphaseI_L = I_{phase}
  • Common in distribution systems
  • Provides neutral connection

Delta (Δ) Connection:

  • VL=VphaseV_L = V_{phase}
  • IL=3 imesIphaseI_L = \sqrt{3} \ imes I_{phase}
  • Common in motors and transformers
  • No neutral point

How to Use This Calculator

  1. Select circuit type: DC, Single-Phase AC, or Three-Phase AC
  2. Enter power requirement in watts or kilowatts
  3. Enter voltage (line-to-line for three-phase)
  4. Enter power factor (for AC circuits, typically 0.8-0.95)
  5. View calculated current and related parameters

Example Calculations

Example 1: DC System (Solar/Battery)
Power: 3000W, Voltage: 48V

I=\ rac300048=62.5 AI = \ rac{3000}{48} = 62.5\,A

Example 2: Single-Phase Motor
Power: 2 HP (1492W), Voltage: 240V, PF: 0.85

I=\ rac1492240 imes0.85≈7.31 AI = \ rac{1492}{240 \ imes 0.85} \approx 7.31\,A

Example 3: Three-Phase Industrial Load
Power: 50kW, Voltage: 480V, PF: 0.90

I=\ rac500001.732 imes480 imes0.90≈66.9 AI = \ rac{50000}{1.732 \ imes 480 \ imes 0.90} \approx 66.9\,A

Practical Applications

  • Wire Sizing: Determining proper conductor size for loads
  • Circuit Breaker Selection: Sizing protective devices
  • Power System Design: Load calculations for installations
  • Energy Management: Monitoring and optimizing power consumption
  • Motor Selection: Matching motors to available power

Important Considerations

  • Always add safety margin (typically 125% for continuous loads)
  • Consider starting currents for motors (5-7× running current)
  • Account for voltage drop in long cable runs
  • Use nameplate power factor if available, otherwise assume 0.85
  • Remember: three-phase systems draw less current per phase for same power

Frequently Asked Questions

Q: Why does three-phase current calculation include √3?
A: The √3 factor accounts for the 120° phase displacement between phases in a balanced three-phase system, allowing more power transfer with less current.

Q: What power factor should I use if I don't know it?
A: Use 0.85 for motors, 0.95 for resistive heaters, and 1.0 for DC circuits or purely resistive AC loads.

Q: How do I convert HP to watts?
A: 1 HP = 746 watts. For example, a 5 HP motor = 5 × 746 = 3730 watts.

Q: Can I use single-phase formulas for three-phase systems?
A: No, three-phase systems require the √3 multiplier. Using single-phase formulas will give incorrect (higher) current values.