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Motor Amperage Formula:
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Motor amperage calculation determines the current draw of an electric motor based on its power rating, operating voltage, efficiency, and power factor. This is essential for proper circuit design and motor protection.
The calculator uses the motor amperage formula:
Where:
Explanation: The formula calculates the actual current drawn by the motor, accounting for energy losses through efficiency and the phase relationship between voltage and current through power factor.
Details: Accurate amperage calculation is crucial for selecting proper wire sizes, circuit breakers, overload protection, and ensuring electrical system safety and efficiency.
Tips: Enter power in watts, voltage in volts, efficiency as a percentage (e.g., 85 for 85%), and power factor as a decimal between 0 and 1. All values must be positive numbers.
Q1: What is power factor and why is it important?
A: Power factor represents the phase difference between voltage and current. Low power factor increases current draw and reduces system efficiency.
Q2: What are typical efficiency values for electric motors?
A: Standard efficiency motors range from 85-90%, high efficiency motors from 90-95%, and premium efficiency motors from 95-98%.
Q3: How does voltage affect motor amperage?
A: Higher voltage reduces amperage for the same power output, allowing smaller conductors and reduced voltage drop.
Q4: When should I use this calculation?
A: Use for motor circuit design, overload protection sizing, generator sizing, and electrical system planning.
Q5: What is the difference between running current and starting current?
A: Starting current (inrush current) is typically 4-8 times higher than running current and lasts only a few seconds during motor startup.