HOLT Electricians Practice Exam

For a 2 horsepower 115 volt motor with a nameplate rating of 22 amperes and a service factor of 1.2, what is the maximum overload protective device relay?

1. 25.5 amperes

2. 30.8 amperes

3. 28.0 amperes

4. 32.0 amperes

The correct answer is: 30.8 amperes

To determine the maximum overload protective device relay for a motor with specific characteristics, you need to first understand the service factor and how it affects the motor's allowed continuous current. For this particular 2 horsepower motor, the nameplate current is rated at 22 amperes, and it has a service factor of 1.2. The service factor indicates how much more load the motor can handle beyond its normal rating without overheating or suffering damage. To calculate the maximum allowable current based on the service factor, you multiply the nameplate current by the service factor. Calculating this gives: 22 amperes × 1.2 = 26.4 amperes This figure represents the maximum current that the motor can continuously handle under normal operating conditions with the service factor taken into account. However, the American National Standards Institute (ANSI) suggests that the overload protection settings should be set between 125% to 150% of the motor's full-load current for typical applications in order to provide adequate protection while allowing for variations in startup and running currents. If you take 125% of the calculated maximum current: 125/100 × 26.4 = 33.0 amperes But since the overflow protective device relay needs to consider the name