from the Forum department...
AC Induction Motor HP Ratings
Engineering and workplace issues. topic
Posted by shivyshivy on 15 October, 2009 - 10:34 pm
Hello all,

While looking at the nameplate of a 4160V cranking motor for a gas turbine I see that there are 2 horsepower ratings. 1 is "Rated HP" of 800 HP and the other simply states "HP" of 920 HP.

Can anyone help me to figure out why the machine has two HP ratings?

Posted by JLo on 3 December, 2009 - 2:39 pm
What you were reading in the motor nameplate was the rated power (800 hp), and the permissible overloading that a motor may be carried continuously at rated voltage and frequency (920 hp). This permissible overloading is obtained by multiplying the service factor (SF), which for most motors is 1.15 times the rated hp of the motor(800 hp x 1.15 = 920 hp). In other words, the 4.16kV motor you were looking at can safely be overload up to 15% above its nominal rating.

I hope it helps,

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