Electrical electronics technology

  In AC induction motor when we start it, at starting it will take 5-7 times of motor rated current and it should come down in 4-5 second and will take no load current 40% - 50% of motor rated current. Then we can now give it on load. Now suppose if there is jam in mechanical coupling side, motor shaft then what would happen. In this case if we start the motor then it take it's starting current 5-6 times of rated current and because it is jam either from mechanical coupling,gearbox or motor shaft problem  Motor can't start rotating and motor will take  current 5-6 times and  will not come down to it no load current as the delay time of EOCR end it will trip in stall fault. So if it trip in stall fault then it is mechanically stuck up, it happens at start. If any queries then do comment. Regards.

If 3 phase Induction motor was in running condition and trip during running in unbalance current.  Probable cause may be :- ​1. Winding resistance unbalance. ​2. Winding inductance unbalance. ​3. Motor shaft play. ​4. Motor vibration may increase. 5. Motor power cable burn somewhere/ carbonized.  May be other cause too. 1. First this is check the motor resistance and inductance by motor checker.  Procedure to check the motor Resistance:-  Disconnect all three motor phase connection from motor terminal , and take out the three lead from stud. Then take reading of resistance of R- phase,Y- phase, B -phase by connecting checker lead to motor phase lead one by one. Resistance should be balance. Procedure to check the motor inductance:-  Disconnect all three motor phase connection from motor terminal , and take out the three lead from stud. Then take reading of inductance of R- phase,Y- phase, B -phase by connecting checker lead to motor phase lead one by one. Induct...

  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 megger.  For LT equipment we use 500volt megger. 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 oh               = 12 Mega ohm. If any queries please comment. Thanks.