Horsepower to Amps Calculator

What is Horsepower to Amps Conversion?

Horsepower to Amps conversion is a crucial calculation in electrical engineering and motor applications. It allows us to determine the current draw (in amperes) of an electric motor based on its power output (in horsepower). This conversion is essential for proper electrical system design, wire sizing, and circuit protection.

Formula

The formula for converting horsepower to amps depends on whether the system is single-phase or three-phase:

For single-phase systems:

\[ I = \frac{HP \times 746}{V \times \eta} \]

For three-phase systems:

\[ I = \frac{HP \times 746}{V \times \eta \times \sqrt{3}} \]

Where:

• \( I \) is the current in Amperes (A)
• \( HP \) is the horsepower
• \( V \) is the voltage (V)
• \( \eta \) is the efficiency (as a decimal)
• 746 is the conversion factor from horsepower to watts

Calculation Steps

Let's calculate the current draw for a 10 HP three-phase motor:

1. Given:
   • Horsepower (HP) = 10
   • Voltage (V) = 480 V
   • Efficiency (\( \eta \)) = 0.85
   • Three-phase system
2. Apply the three-phase formula: \[ I = \frac{HP \times 746}{V \times \eta \times \sqrt{3}} \]
3. Substitute the known values: \[ I = \frac{10 \times 746}{480 \times 0.85 \times \sqrt{3}} \]
4. Perform the calculation: \[ I = \frac{7460}{480 \times 0.85 \times 1.732} \approx 13.52 \text{ A} \]

Example and Visual Representation

Let's visualize the relationship between horsepower and current for a three-phase motor:

This diagram illustrates:

• The x-axis represents the motor's horsepower
• The y-axis represents the current draw in Amperes
• The red curve shows how current increases with horsepower
• The motor symbol represents the conversion of electrical power to mechanical power
• The blue arrow represents power input (horsepower)
• The green arrow represents current output (Amperes)