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Single-Phase Motor Current Formula:
The motor current calculation determines the electrical current drawn by a single-phase AC motor based on its power rating, supply voltage, power factor, and efficiency. This is essential for proper circuit sizing and protection.
The calculator uses the single-phase motor current formula:
Where:
Explanation: The formula accounts for both the power factor (ratio of real power to apparent power) and motor efficiency to calculate the actual current draw.
Details: Accurate current calculation is crucial for selecting proper wire sizes, circuit breakers, and overload protection devices to ensure safe motor operation and prevent electrical hazards.
Tips: Enter power in watts, voltage in volts, power factor (typically 0.8-0.95 for motors), and efficiency (typically 0.75-0.95). All values must be positive numbers.
Q1: What's the difference between single-phase and three-phase current calculation?
A: Three-phase calculation includes a √3 (1.732) factor and may use line-to-line voltage. The formula is different.
Q2: What are typical power factors for motors?
A: Induction motors typically have 0.8-0.9 PF at full load, lower at partial loads. Power factor decreases as load decreases.
Q3: Why include efficiency in the calculation?
A: Motors convert electrical to mechanical power. Efficiency accounts for losses (heat, friction) that increase current draw.
Q4: How does voltage affect current?
A: Current is inversely proportional to voltage. Lower voltage increases current draw for the same power output.
Q5: What safety margin should I add?
A: For circuit protection, add 25% to the calculated current to account for startup surges and variations.