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Old January 3rd, 2018, 03:20 PM   #3
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Bit_Bucket_07 is offline
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Join Date: Feb 2013
Location: Southeast US
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Originally Posted by James Mcquade View Post

the motor service factor is how much the motor can run above its rated current for a short time without damaging the motor.

for example, you have a motor rated at 230 volts and 2.1 amps.
the service factor means that the motor can run at 2.1 x 1.15 = 2.415 amps
for a short period of time without damaging the motor. (I made the numbers up)

as the voltage goes down, the motor current will go up, so a motor at 208 volts will require more current than a motor at 230 volts.

you must look at the motor legend for full load amps or look at the motor specs. the SF has nothing to do with the overload, you must use the contactor selection chart for motor overloads.

I agree, with one exception. The SF represents the percentage of rated HP that the motor is designed to endure temporarily, rather than the percentage of FLA that the motor can temporarily endure.

Many motors will list the SF Amperage as "SFA" on the motor nameplate.
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