Precommissioning Checks for an Induction Motor

Here are some:

• Has the motor been correctly selected for the hazardous area zone and temperature class?
• Record the motor nameplate data.
• Is the motor correctly sized for the mechanical load?
• Is the motor secure on its mounting?
• Is the coupling between the motor and the load correctly installed and aligned?
• Is the guarding correctly installed?
• Is the earth connection correct and proven?
• Are the phase connections correct and tight?
• Is the cable gland correct for the hazardous area zone and temperature class?
• Is the cable gland assembled correctly?
• Is the terminal box cover secure to the correct IP rating?
• Is the motor overload protection device correctly adjusted?
• Are the motor fuses correctly selected and secured?
• Does the motor starter work correctly in "test" mode?
• Does the motor isolator work correctly, preventing the starter operating in "test"?
• Ditto for the emergency stop button?

Other readers - please add to this list!

There are two types of checks you can carry out before commissioning.

Mechanical Checks

1- Check the alignment of the driving motor with the driven machine.

2- Check the adequacy of foundation and size of foundation bolts and tightness of the motor to the foundation.

3- Check the around working clearance for safe operation and easy maintenance.

4- Check whether the vibration is within permissible limits.

5- Check the method of cooling and ensure that the requirement under IC classification is satisfied.

6- Check the degree of protection against ingress of solid bodies/particles and liquids and ensure that the requirement under IP classification is satisfied.

7- Check the bearings and air gap between stator and rotor.

There are quite more I've just listed a few.

Electrical Checks

1- Check whether facility to isolate the supply is provided within 3 metres. If push button switch is provided as isolation device, it should be provided with facility to lock.

2- Check the size of cable for conformity with the approved drawing.

3- Check the cable termination for

1. Proper crimping of cable conductors – check whether cable glands are of proper size and glanding is done properly.
2. Proper seating of conductor sockets at motor terminals- check whether spring washers are used.
3. Check the size of earthing conductor of glands. The size should be same as that used for the motor .
4. Clamping of the cable at a distance of 45 cms from the termination.
5. Check whether cables are taken straight from the termination at the terminal box – there shall not be any tangential stress at the glands.
6. Check whether double compression glanding is used in hazardous areas.

4- Check whether duplicate earthing is provided for the body of the motor from diametrically opposite sides – check the size of the earthing conductors for adequacy.

5- In hazardous areas, check whether earthing is done from inside of terminal boxes.
6- Check the earth lead terminations and connections for

1. socketing of the earth lead ends (if round conductor)
2. proper surface contact.
3. removal of paint on the body of the equipment
4. tinning of copper flats at terminations
5. effectiveness of bolting
6. check whether starting devices as per the approved scheme are provided for the motor.

5- Check the cable connection from slip ring motors to rotor resistance cubicle.
6- Check the enclosure of rotor resistance. The rotor resistance shall be inaccessible and enclosed for safety.
7- Check the length of flexible connections to movable motors. The length shall be limited to 60 cms.
8- Check whether flexible cables are enclosed in steel re-inforced PVC flexible conduits.
9- Check the terminations for use of proper couplings and for adequate mechanical strength.

In case of your motor being MV check whether ammeters of adequate rating is provided in the capacitor circuit. Check the utilisation category of contactors used in starters. The standardized utilisation categories of contactors for common applications of ac motors are given below: AC-1 Non inductive or slightly inductive loads – resistance furnaces. AC-2 Slip ring motors: starting-switching off. AC-3 Squirrel cage motors: Starting, switching off during running. AC-4 Squirrel cage motors: Starting, plugging, inching. Check the current rating of the contactors and ensure that it is suitable for the motor for which it is used. Check whether the settings of over current relays in starters correspond to the motor loading. Check whether the protective arrangements provided are as per the approved scheme. Check the motor protection relays for the number of elements/ protections and their settings. Check whether relays are tested and set to suit the operating conditions. Check the rating of back up fuses for conformity with the approved scheme.

I know there are a lot of checks you can carry out. Ive just listed a few. I hope this info will answer your question.

Regards,

DG EE