Pertaining to the service factor rating on an AC 3PH motor: Correct me if I am wrong: the service factor rating value is a multiplier that is used to calculate the HP that the motor can provide above the rated (nameplate) HP. Before anyone explains why this rating should not be used when designing applications, keep in mind I have no intention of using this rating to get extra out of our motors. This is just for my own understanding.
We recently had an issue where an existing motor driving a fan and the fan shaft mount worn out. The fan was replaced but the new one had a more aggressive blade pitch and thus put more of a load on the motor. The motor is 460VAC, 3PH, 2HP, 60Hz, across the line contactor for control, and heater overloads for over-current protection (old system that will not be upgraded). The heater overloads continually trip out because of the increased load. One of our associates said why don't we just put in bigger heater overloads? This, of course, was not the correct solution, but it got me thinking.
Here is my question: If the service factor is a multiplier of the HP rating, is there a way to relate this multiplier to the motor current? If our 2 HP motor has a SF of 1.15, then it can produce 2.3 HP. What is the motor current at this rating? Correct me if I am wrong, but multiplying the FLA rating by the SF does not give a correct value. Or, is this one of those situations where there are too many variables for a generic relationship to be established, and each specific system would need to be analyzed individually? Or is there something I am missing totally?
Thanks for any feedback in advance.
We recently had an issue where an existing motor driving a fan and the fan shaft mount worn out. The fan was replaced but the new one had a more aggressive blade pitch and thus put more of a load on the motor. The motor is 460VAC, 3PH, 2HP, 60Hz, across the line contactor for control, and heater overloads for over-current protection (old system that will not be upgraded). The heater overloads continually trip out because of the increased load. One of our associates said why don't we just put in bigger heater overloads? This, of course, was not the correct solution, but it got me thinking.
Here is my question: If the service factor is a multiplier of the HP rating, is there a way to relate this multiplier to the motor current? If our 2 HP motor has a SF of 1.15, then it can produce 2.3 HP. What is the motor current at this rating? Correct me if I am wrong, but multiplying the FLA rating by the SF does not give a correct value. Or, is this one of those situations where there are too many variables for a generic relationship to be established, and each specific system would need to be analyzed individually? Or is there something I am missing totally?
Thanks for any feedback in advance.