Environmental Parameters:motor

There are a number of factors to consider relating to the environment in which the motor is operated.

 

Operating temperature(s) -- Specifies the rated temperature or range of temperatures that the motor is designed to operate at. Before a motor is started, its windings are at the temperature of the surrounding air (known as ambient temperature). Temperature in the motor will rise as soon as it is started. The combination of the ambient temperature and the allowed temperature rise equals the maximum winding temperature in the motor. Operating a motor in environments above the rated temperature will result in a derating of the motor continuous torque, while operating in extremely cold environments may require a different bearing lubrication.

 

Insulation rating -- The National Electrical Manufacturers Association (NEMA) has established insulation classes to meet motor temperature requirements found in different operating environments. The four insulation classes are A, B, F, and H. Class F is commonly used. Class A is seldom used. NEMA has standardized an ambient temperature of 40° C, or 104° F within a defined altitude range for all motor classes. Each insulation class has a specified allowable temperature rise.

 

Shock rating -- Shock rating is the maximum shock the motor can stand and still meet operating specifications. Shock is expressed in units of acceleration (distance/time2), most commonly in g's as a multiple of the earth's standard acceleration due to gravity.

 

Vibration rating -- Vibration rating is the maximum vibration the motor can withstand and still meet operating specifications. Vibration is expressed in the same units as shock, based on acceleration.

 

Enclosure rating -- Enclosures are used to isolate motor components and protect them from the external environment. They are often rated or designed for different types of protection.

 

Dust-proof -- Dust-proof motors protect against dust infiltration with features such as total enclosure and labyrinth seals for shafts. The IP (Ingress Protection) rating for dust-proof motors is IP6x.

 

Drip-proof -- Drip-proof motors contain ventilation openings that are designed so that drops of liquid or solid particles falling from any angle within 15 degrees of vertical cannot enter the motor. Motors with an IP rating of IPx1 through IPx9 are considered drip-proof.

 

Explosion proof -- Explosion-proof motors have totally enclosed housings that are constructed to withstand internal explosion of a specified gas, vapor, or dust. Should such an explosion occur, the enclosure would prevent the ignition or explosion of the gas or vapor surrounding the motor enclosure. Several explosion-proof ratings are governed by Underwriter's Laboratories (UL).

 

Totally enclosed -- Totally enclosed motors have an enclosure that prevents free exchange of air between the inside and the outside of the enclosure. Common ratings are TEFC (fan-cooled) and TENV (non-ventilated); this is not an airtight rating. These motors are most frequently used in potentially contaminated environments.

 

Waterproof -- There are several degrees of waterproofing applicable to motors and they are reflected in the IP rating for the motor:

IPx1 - Protection against vertically falling drops of water (drip-proof).

IPx2 - Protection against direct sprays of water up to 15 degrees from vertical.

IPx3 - Protection against direct sprays of water up to 60 degrees from vertical.

IPx4 - Protection against water sprayed from all directions.

IPx5 - Protected against low pressure jets of water from all directions.

IPx6 - Protected against high pressure jets of water from all directions.

IPx7 - Protected against the effects of immersion up to 1 meter.

IPx8 - Protected against long periods of immersion under pressure.

Some motors may also be rated for use in special or extreme environments such as clean rooms, vacuum chambers, and cryogenic temperatures.