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Selecting the right motor environment

04 February, 2019

Rob Wood, ABB’s UK sales manager for LV motors, examines aspects of an electric motor’s operating environment that you need to consider when choosing and specifying a machine.

Knowing a motor’s environment helps with the selection of enclosure type, cooling method and bearing lubrication intervals. Ambient temperature, humidity and altitude all affect a motor’s performance and need to be considered. For instance, the thinner air at altitudes higher than 1,000 metres above sea level compromises motor cooling and can impact insulation capability. This may mean that the motor power needs de-rating and the insulation upgrading.


Explosive atmospheres

Motors for use in explosive atmosphere need special attention. Equipment is grouped according to the location above or underground and the type of explosive atmosphere for which it is intended. Explosive atmospheres are divided into zones according to the risk posed by explosive gas or dust. Equipment protection levels (EPLs) indicate the ignition risk that the equipment poses. The temperature class needs to be considered for motors in such areas and depends on the ignition temperature of the flammable gas or dust, as well as the subgroup of the gas and dust. If in doubt, consult the motor manufacturer.


Enclosure type

For motors used in very dusty or wet areas, the corrosion protection and type of enclosure should be considered. Selecting the right surface treatment will help to prolong the life of the motor and reduce the need for maintenance.

Enclosures offer levels of protection against dust and water ingress. Ingress protection (IP) ratings for motors start at IP23, which allows for light water sprays, and go up to IP66, which is both dust-tight and can withstand powerful water jets. 


Cooling methods

These are defined by International Cooling, or IC, codes. The code includes a letter to denote the cooling medium, which is usually air, but may be water or other fluids. If the primary coolant is air, the A is omitted for simplified designation. If the coolant is something other than air, the letter is included. 


The code also contains two digits. The first digit signifies the type of cooling circuit in use: open machine; enclosed machine; or heat exchanger fitted. The second digit signifies the fan type: none; self-driven; or external. Where a secondary coolant is used, the information describing the coolant type and circulation method is repeated.  


The IC411 totally enclosed fan-cooled (TEFC) motor is the predominant standard for industrial applications today. The versatile TEFC is a totally enclosed construction, with cooling air being directed over the frame by a shaft-mounted fan.  


For more information, you can view this video:

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