What is the standard time rating for a continuous duty rated electric motor?

• A. 12 hours
• B. 24 hours
• C. 48 hours
• D. 72 hours

Answer: (B)

The time rating being tested is about how long a motor can run at its rated load without overheating—the duty it’s designed for. A continuous duty rated electric motor is intended to run non-stop at its rated load, essentially all day. That’s why the standard time rating is 24 hours: a full day of operation within cooling limits is expected for continuous duty. The other options would imply shorter stopping periods or atypical cycling, which isn’t what continuous duty means. In practice, many motors labeled for continuous or 24/7 operation are designed to handle running around the clock under normal cooling conditions.