HOLT Electricians Practice Exam

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The input VA of a 3 horsepower 208-volt single-phase motor is?

2890 VA
3390 VA
3890 VA
4390 VA

The correct answer is: 3890 VA

To calculate the input VA (volt-amperes) of a 3 horsepower motor operating at 208 volts in a single-phase system, you can use the formula that relates horsepower to VA. One horsepower is equivalent to approximately 746 watts. Therefore, to convert horsepower to watts, you multiply the horsepower by 746. For a 3-horsepower motor: \[ \text{Power (watts)} = 3 \text{ HP} \times 746 \text{ watts/HP} = 2238 \text{ watts} \] In a single-phase circuit, the apparent power in VA can be calculated using the formula: \[ \text{VA} = \frac{\text{Power (watts)}}{\text{Power Factor}} \] Assuming a typical power factor of 0.9 (which is common for motors), the calculation becomes: \[ \text{VA} = \frac{2238 \text{ watts}}{0.9} \approx 2486 \text{ VA} \] However, if you want a more direct approach considering the standard practice, you can multiply the horsepower directly by a factor that incorporates both the power factor and voltage: