In Current Affairs™ #4 we talked about the need to apply ac motors within the proper voltage and frequency range. A related topic that prompts frequent questions is the effect of ac motor service factor on selection and application.
Service factor is a multiplier that is applied to the motor’s normal horsepower rating to indicate an increase in power output (or overload capacity) that the motor is capable of providing under certain conditions. Common values of service factor are 1.0, 1.15, and 1.25. Any service factor greater than 1.0 must be indicated on the motor nameplate; in some cases the running current at service factor loading is also indicated on the nameplate as service factor amperes or SFA.