Answer: LA is installed outside and the effect of lightning is grounded, whereas surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of the surge.
Answer: Actually the thing is vacuum has a high arc quenching property compare to air because in VCB, the die electric strengths equal to 8 times of air. That y always vacuum used as in HT breaker and air used as in LT
Answer: The shunt connection in the four-point stater is provided separately from the line whereas in three-point stater, it is connected with a line which is the drawback in three-point stater
Answer: There are two types of exciters, static exciter, and rotary exciter. The purpose of the exciter is to supply the excitation dc voltage to the fixed poles of the generator. A rotary exciter is an additional small generator mounted on the shaft of the main generator. If it is a dc generator, it will …
Answer: Yes because the poles changes for every half-cycle of ac voltage so the polarity of AC voltage is continuously changing for every half cycle. So, interchanging of terminals in ac system does not show any difference. That’s why the ac solenoid attract the plunger even though its terminals are interchanged.
Answer: For the generation of elect power we need a prime mover which supplies mechanical power input to the alternator, can be steam turbines, or hydro turbines. When poles of the rotor move under the armature conductors which are placed on the stator, field flux cuts the armature conductor, therefore voltage is generated and is …
Answer: ELCB is used to detect earth leakage faults. Once the phase and neutral are connected in an ELCB, the current will flow through the phase and that much current will have to return neutral so the resultant current is zero. Once there is a ground fault on the load side, current from the phase …
Answer: Series motor cannot be started without load because of high starting torque. Series motor is used in Trains, Crane, etc.
Answer: It depends upon R=rho l/a where the area(a) is inversely proportional to resistance(R), so if (a) increases, R decreases & if R is less the leakage current will take a low resistance path so the earth pin should be thicker. It is longer because the First to make the connection and last to disconnect …
Answer: For lighting loads, a neutral conductor is a must and hence the secondary must be star winding and this lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta/star transformer is used for lighting loads.
Answer :(1). The main advantage of using the star delta starter is the reduction of current during the starting of the motor. Starting current is reduced to 3-4 times Of current of Direct online starting. (2). Hence the starting current is reduced, the voltage drops during the starting of motor in systems are reduced
Answer: In DC motors, Voltage equation is V=Eb-IaRa (V = Terminal voltage, Eb = Back emf in Motor, Ia = Armature current, Ra = Armature resistance).At starting, Eb is zero. Therefore, V=IaRa, Ia = V/Ra, where Ra is very less like 0.01ohm. i.e, Ia will become enormously increased.