Electrical electronics technology

when we connect three phase applied to stator winding then rotating flux will set up due to this flux rotor start rotating but it will never catch up the synchronous speed of flux Ns=120 f/p. if it did so then no relative speed between flux and rotor then no EMF will induces, no current and so no torque to maintain rotation. So motor will always rotate less than synchronous speed of magnetic flux Ns = 120 f/p. The difference between synchronous speed and actual speed Nr is known as slip.      Slip = Ns - Nr.  Unit revolution per second. Express percentage of synchronous speed  % slip S = ( (Ns -  Nr) /NS) * 100 % One more term we call it as slip speed Slip speed = sNs = Ns- Nr  when rotor is stationary then frequency of rotor current is same as supply frequency. But when rotor start rotating then frequency depend upon relative speed between the two rotating magnetic flux and rotor. Let's say at any sleep Speed the frequency of rotor current is f' . Ns ...

Induction motor has a stationary part known as stator containing status winding and a rotor having bar in squirrel gauge induction motor and three phase winding in slipping induction motor. When three phase winding of stator fed by three phase supply then a rotating magnetic field  of constant magnitude 1.5 times  of maximum flux due to any phases is generated. Rotating at synchronous speed NS = 120 f/p.  This flux passage through the air gap and cut the rotor bar as that they are still stationery. Due to the relative velocity between the rotating flux and the stationary rotar conductor, EMF is induced in the rotor conductor according to faraday's law of electromagnetic induction. The the frequency of the induced EMF is same as supply frequency, magnitude is proportional to the relative velocity between the two rotating flux and rotor conductor. And direction is given by Fleming's right hand rule. since the rotor conductors are short circuit by end ring so current start f...

  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.