Electric Motor Service Factor Definition

The rated horsepower of an ac motor to the rated armature current of a dc motor or.

Electric motor service factor definition.

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. Motor service factor is probably the most misunderstood value on a motor nameplate. Service factor is an indicator of the amount of overload a motor can be expected to handle for example a motor with a 1 0 service factor cannot be expected to handle more than its nameplate hp on a continuous basis. The americas water systems group serves north and south america.

The canadian electrical code defines service factor as a multiplier that when applied to. Franklin electric offers a full line of pumping systems to serve a wide variety of clean water applications. A 1 15 service factor motor can be. 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.

For example the maximum motor load for a 1hp electric motor with a service factor of 1 15 is. Most hazardous location motors are made with an sf of 1 0 but some specialized units are available for class i applications. Typical service factors sf for ac motors. Likewise for each power and speed the mg 1 standard defines a frame number which is linked to the service factor.

To most it seems quite simple. This means that the motor can operate at 100 of its rated power. As per the standards a motor s nameplate should indicate the service factor as sf. 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.

In these cases a motor with a service factor of 1 15 can be applied to the rated power. However motor operation under these conditions leads to many performance issues down the road. The nema national electrical manufacturers association standard service factor for totally enclosed motors is 1 0. Motors of 10 hp and up usually have a service factor of 1 15.

A motor with a 1 15 service factor can be expected to safely handle infrequent loads to 15 past it s rated horsepower. 1 15 x 1 1 15hp anything above this load will certainly result in motor overheating and consequent damage of the ac motor. In the u s the defacto standard for ac motors is the nema standards. Some applications require a motor that can exceed the rated power.

The service factor sf is a measure of periodically overload capacity at which a motor can operate without damage. The standard which defines the service factor for motors and generators is the mg 1 standard which in turn defines powers and speeds. The service factor sf is commonly misunderstood as an allowable overload for electric motors. 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.