Service Factor
The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage
Sponsored Links
The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage. The NEMA (National Electrical Manufacturers Association) standard service factor for totally enclosed motors is 1.0.
A motor operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating at at its rated nameplate horsepower.
NEMA Service Factor at Synchronous Speed (RPM) for drip proof motors:
| Power (HP) |
Service Factor - SF | |||
| Synchronous Speed (RPM) | ||||
| 3600 | 1800 | 1200 | 900 | |
| 1/6, 1/4, 1/3 | 1.35 | 1.35 | 1.35 | 1.35 |
| 1/6 | 1.25 | 1.25 | 1.25 | 1.25 |
| 3/4 | 1.25 | 1.25 | 1.15 | 1.15 |
| 1 | 1.25 | 1.15 | 1.15 | 1.15 |
| 1 1/2 and up | 1.115 | 1.15 | 1.15 | 1.15 |
Example - Service Factor
A 1 HP motor with a Service Factor - SF = 1.15 can operate at
1 HP x 1.15
= 1.15 HP
without overheating or otherwise damaging the motor if rated voltage and frequency are supplied to the motor.
Insulation life and bearings life are reduced by the service factor load.
Sponsored Links
Sponsored Links
Engineering ToolBox - SketchUp Edition - Online 3D modeling!
Engineering ToolBox - SketchUp Edition - enabled for use with the amazing, fun and free Google SketchUp.
Search the ToolBox
© The Engineering ToolBox 2005
9 12 8
