Methods of "Drying Out" Electric Motor used with Air Compressor.

Though you have installed your electric motor with all the pre-commissioning check-ups,sometimes any accident happens to your motor and it needs to give
attentation before using it again.If any water or any moisture observed in electric motor,it should be dried out.This will ensure safe running of motor as wel
as Air Compressor.

Various methods are available for "Drying Out" electric motor,but we will see ,the methods which are possible in practical use.In any plant all the facilities
are not available at same time,in this it is very important to use the method which is most suitable at that moment.You can use any method from below.

Methods of "DRYING OUT" Electric motor.

01)A convenient method of drying out electric motor is to block the motor so that it can not rotate and apply a very low voltage of about 10% of the normal
to the starter terminals.
In case of Slipring Motor,the rotor windings should be short circuited.
Close supervision is necessary during the process of "Drying Out" with this method.The heat generated in the windings is not easily dissipated and one part
of the winding may be exceedingly hot before another part has had time to expel the moisture.This may be deviated to some extent by taking every
precaution to exclude draughts from exposed parts of windings.

02)The electric motor which is used to run Air Compressor can be placed in an oven,if available,but the temperature shall not be allowed to exceeds
85 degree centigrate.Alternatively,hot air can be blown into the motor.The air must be clean & dry at a temperature not more than 85 degree centigrate.

03)The electric motor can be dried out by placing 6 to 12 carbon filament lamps (According to the frame size of the motor) closer arround the frame of
motor,properly hung to the fixtures for more than 24 hours under observation.

04)By applying DC Current (Not more than 80 % of the motor rated current) contineously to the stator of the motor,the large motor can be dried out.An added
advantage of DC current is the easy control of DC current through "rheostat"

Some points must kept in mind while "Drying Out" of Electric Motor.

While the motor is in drying out process,the small vents,if provided,on both the sides of motor should kept open for escape of moisture.A tested temperature
gauge( capillary type) should be placed on the motor to record the optimum temperature the windings achieved and to control the temperature to below
85 degree centigrate.It is necessary to cover the motor with asbestos clothing to prevent heat radiation.

Insulation resistance must be measured at an interval of every hour till the insulation value stabilizes at certain point,then the heating process is to be
discontinued.When the motor cools down to the ambient temperature will get favourable insulation resistance reading.

Now you can use Electric Motor with Air Compressor.

prasanna
http://www.pnengineering.blogspot.com/

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