Electric Motor Service Factor Definition

Motors of 10 hp and up usually have a service factor of 1 15.

Electric motor service factor definition.

The service factor sf is a measure of periodically overload capacity at which a motor can operate without damage. For example the maximum motor load for a 1hp electric motor with a service factor of 1 15 is. This means that the motor can operate at 100 of its rated power. The nema national electrical manufacturers association standard service factor for totally enclosed motors is 1 0.

However motor operation under these conditions leads to many performance issues down the road. As per the standards a motor s nameplate should indicate the service factor as sf. In the u s the defacto standard for ac motors is the nema standards. In these cases a motor with a service factor of 1 15 can be applied to the rated power.

Motor service factor is probably the most misunderstood value on a motor nameplate. The canadian electrical code defines service factor as a multiplier that when applied to. To the rated output of a generator. The standard which defines the service factor for motors and generators is the mg 1 standard which in turn defines powers and speeds.

A 1 15 service factor motor can be. The service factor sf is commonly misunderstood as an allowable overload for electric motors. Some applications require a motor that can exceed the rated power. The americas water systems group serves north and south america.

1 15 x 1 1 15hp anything above this load will certainly result in motor overheating and consequent damage of the ac motor. The rated horsepower of an ac motor to the rated armature current of a dc motor or. Franklin electric offers a full line of pumping systems to serve a wide variety of clean water applications. Likewise for each power and speed the mg 1 standard defines a frame number which is linked to the service factor.

A motor with a 1 15 service factor can be expected to safely handle infrequent loads to 15 past it s rated horsepower. Most hazardous location motors are made with an sf of 1 0 but some specialized units are available for class i applications. Most motors have a duty factor of 1 15 for open motors and 1 0 for totally closed motors. For example you may find a 100 hp motor with a sf of 1 15 driving a 110 hp load under the incorrect assumption that it tolerates up to 115 hp.

If it is a 1 0 you can run a motor to 100 load if it is 1 15 then it can be loaded to 115 of its rated load. 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. Typical service factors sf for ac motors. Traditionally totally enclosed fan cooled tefc motors had an sf of 1 0 but most manufacturers now offer tefc motors with service factors of 1 15 the same as on odp motors.