What is the minimum value of insulation resistance of an electrical equipment so we can give it in service? How to improve IR of motor ?

What is the minimum value of insulation resistance of an Low tension electrical equipment so we can give it in service?

Well " insulation resistance"  this is very basic term in electrical world.

If some motor, switchgear, transformer trip in Earth fault then we need to check the insulation resistance of the equipment with meger. 

For LT equipment we use 500volt meger. Our equipment is generally of 415 volt ac. So the minimum IR value formula is 

IR min. = KV +1 MEGA OHM.

SO if the voltage is 415 vac then min. Value of IR  will be

IR  = 0.415 +1 Mega ohm

      = 1.415 Mega ohm.

 

If voltage level is 11kv then min. Value of insulation resistance will be

IR min. = 11kv + 1 Mega ohm

             = 12 Mega ohm.

If motor IR of motor at lower side let's say below 2Mega Ohm then what should we do to improve the IR of motor.

Well if motor Insulation is really damage and grounded then it will give you 0 Mega ohm but if it is non zero value then you have a chance to get healthy motor, low IR  may be the because of moisture.

First put blower near the motor terminal let it run for 24 hours so moisture get vaporize. Then put off the blower and wait for 30 minutes and then check IR .

If not improve then send it to the motor repairing center there they will open the motor and dry the stator section part by heating chamber.

By doing this they heat the stator part of motor and dry the stator part. It will definitely work.

By using above step you can improve insulation resistance of motor.

If any queries feel free to comment.

Thanks.