How Hot is Hot?

My motor is running hot!

This is a common lament we’ve heard countless times at Flolo.

How Hot?“, we ask the customer.

I can’t put my hand on it,” comes the response.

Well, that begs the question, how much heat can your hand safely tolerate? The average human can handle about 140 degrees F depending on a number of factors.

Now, let’s compare this to the operation of an electric motor. Many motors nowadays are being manufactured with Class F insulation. The temperature rating of Class F insulation is 155 degrees C which converts to 311 degree F. Now that’s hot!

Of course, the motor designer is not going to use the entire margin he has and make the motor run right at the maximum allowable temperature. But a motor will certainly generate heat and the frame designed in such a way as to dissipate that heat. A rolled steel frame will be hotter because the surface area is closer to the winding. A large cast iron frame with cooling fins will dissipate the heat faster and run cooler.

Heat is the biggest cause of failure for motor insulation which is why motors are not designed to run at maximum temperature all the time. The higher the motor temperature, the shorter the insulation life will be. Nevertheless, most electric motors will be hot so using the hand method to check the temperature is generally not the best idea.

For more information on heat and how it effects your motors contact your Flolo sales representative today.