• AREA CLASSIFICATION THAT MOTOR IS TO BE USED IN.

  • KW RATING AND SPEED REQUIRED.

  • MOUNTING REQUIRED

  • ELECTRICAL SUPPLY DETAILS

  • CONSTRUCTION OF MOTOR.

  • BEARINGS

  • PAINTING

  • TESTING

  • INSULATION

  • DOCUMENTATION

In writing a motor specification, their are various items that must be considered to ensure that the motors are specified correctly.These are as follows:

HOW TO SPECIFY A MOTOR FOR A NEW PROJECT(NEW BUILDINGS E.T.C)

AREA CLASSIFICATION

This must be taken into consideration as it determines the type of motor that can be used.

For the normal non-hazardous area, a Totally Enclosed Fan Cooled (TEFC) motor is suitable. These are available with various enclosure ratings such as IP54, IP55, IP56, IP65, IP66 and IP67. The difference in the rating is explained in AS1939.

As a rough rule of thumb, the following is applicable.

  • IP54 Weatherproof

  • IP55 Light hose proof

  • IP56 High-pressure Hose proof

  • IP65 Complete protection against entry of dust and light hose proof

  • IP66 Complete protection against the entry of dust and high-pressure hose proof

  • IP67 Protection against immersion

For hazardous areas, it is extremely important that the correct motor is chosen.

Also, the ambient temperature range of operation must be stated as this can determine the class of insulation to be used and, in some instances, may require special grease in the bearings.

KW RATING AND SPEED

These are determined by the driven equipment and are generally a mechanical consideration rather than electrical.

There are standard ratings available as set down in AS1359. 30.

The speed of the motors is determined by the number of poles and the frequency of the supply.

The following approximations are applicable.

The actual full load speed will depend upon the motor design.

MOUNTING REQUIRED

These are explained in detail in AS1359.22.The usual methods are as follows:

  • Horizontal foot (B3) IM1001

  • Horizontal flange (B5) IM3001

  • Horizontal foot and flange (B3/B5) IM2001

  • Vertical flange (V1) IM3011

ELECTRICAL SUPPLY DETAILS

The voltage, phase and frequency of supply must be stated complete with tolerances required.

The correct voltage, on which the motor is required to operate, is important as this can change the characteristics of the motor for no apparent reason. If the voltage decreases by 5% the starting torque of the motor will decrease by 10%. This could mean that the motor will now not develop enough torque to start the load

The voltage tolerance must be also stated, such as +/- 10%. This will ensure that the motor will operate correctly over the range.

It must be shown in the specification if the motor is to operate on three phase or single phase as different motors are required.

The frequency of the supply must be stated as this can change the speed. Again the tolerance must be stated

Please refer previous comments under kW rating and speed for examples of how frequency can affect the speed.

CONSTRUCTION OF MOTOR

The physical requirements of the motor must be shown. This will include such items as cast iron frame, plastic fans etc.

Please refer to the examples of specifications which provide the details required.

BEARINGS

The requirement for the bearings must be stated. This should include Brand name, ball or roller and method of greasing.

Again refer to the examples of specifications which provide the details required

PAINTING

Clear and precise details of the paint finish must be given. For severe chemical duty it may require the motor to have a special epoxy paint finish. The type of paint required, Brand name and final colour should be stated.

Again refer to the examples of specifications which provide the details required

TESTING

It is important to state what testing is required. This can vary from a routine test to a full performance test. Please refer to AS1359.60 which details the different type of tests

INSULATION

This is very important as it will determine the final surface temperature that is acceptable and also affect the expected life of the motor. The types available are:

  • A Class 105

  • E Class 120

  • B Class 130

  • F Class 155

  • H Class 180

The selection will depend upon the ambient temperature in which the motor is to be used. Please refer to AS1359.32 which provides details of the different types of insulation.

The normal standard insulation is Class F with Class B rise.

DOCUMENTATION

It is important to state in the specification what documentation you require to be submitted. This can vary from simple outline dimension drawings and type test certificates to exploded view drawings, SAA certification and as made drawings

Contact Us
United Kingdom

Electric Motors International Limited

Unit 207, 26,27,Cheering Lane,

London E20 1BD.

United Kingdom.

+ 44 208 935 5015

+ 44 208 929 8099

sales@emimotors.com

Fax

Denmark

Electric Motors International APS

Unit 45,

No. 2 Porsvej 
Aalborg, 9000

Denmark

+45 36 98 83 88

sales@emimotors.dk

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