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## manishpd86

1. What is the 3 ph transformer ?A. A 3ph transformer is that transformer which is equivalent to  three single phase transformer but wound on one core and enclosed within one common case.Q2. What is the advantage is obtained in the delta connection ?A. When three transformer are obtained in delta, one may be removed and two remaining unit will carry 57.7% of the original three phase load and thus maintain the continuity of supply.Q3. What advantage has the star connection over the delta connection ?A. Each star connection transformer is wound for only 57.7% of line voltage . In hv transmission, this admits of much smaller transformer being built for high voltage than possible with delta connection, because of less insulation.Q4. How to connect two single phase transformer to give three phase o/p from a three phase I/p ?A. They would have to connect in an open-delta.Q5. What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?A.	Each transformer is only capable of supplying 86.6%of its o/p rating.1. What is the operating principle of syn. generator?A. A syn. generator is a sync. machine which receives mechanical energy from prim mover to which it is mechanically coupled and delivers electrical energy.Q2. What are the essential elements for generating emf in alternator ?A. Prime movers, stator, rotor and exciter.Q3. What type of rotor is adopted for high speed alternators ?A. Cylindrical or non salient pole rotor1.  What is the torque developed dy the single phase induction motor at syn.speed zero?A.Negative torque.Q2. Why this motor are ususaly set on the rubber spring mounts ?A.Because pulsating torque is developed as a direct consequence of the pulsating power in the single phase circuit.Q3. Why the normal full-load slip of the single phase induction motor higher than that of 3 phase induction motor ?A. Because of owing to development of backward rotating field. The power is to be delivered to the backward field from the power converted into mechanical power by the fwd field.Q4. How can the shaded pole motor be reversed in the direction of rotation, give region of your answer?A. Cannot reversed because the machine is constructed so that the shading coil can be shifted to the other side of the pole.Q5. What type motor use in the ceiling fans ?A. Split phase capacitor type single phase induction motor.Q4. What is the max. speed of a 50 Hz alternator ?A. 3,000 rpm.Q5. which alternator is most stable ?A.	Salient pole alternator.1. What is the double revolution field theory (Ferraries principle)?A. This theory is based on the idea that pulsating field produced in a single phase motor can be resolved into two components of half its amplitude and rotating in opposite direction with synchronous speed .Q2. What is the cross field theory ?A. The field created by the rotor current becomes max. nearly one-forth cycle after the generated emf has reaches its max. values since the field created by rotor current is at right angle to the field by the stater current it is known as Cross-Field.Q3. What are the starting methods of single phase induction motor ?A. Resistance start, capacitor start, capacitor start capacitor run, permanent capacitor , shaded pole.Q4. What is split phase motor ?A. This is the single phase induction motor equipped with an auxiliary winding, also called the starting winding, connected in parallel with the main winding on stator and differing from it in both phase and space. The starting winding is usually open by the centrifugally operated device when the motor attains a predetermined speed.Q5. How the direction of rotation of single phase induction motor reversed ?A.	It can change either by reversing the lead to the main or starting winding but not both.Q1.What is the principle of the DC Motor ?A. If the current carrying conductor is placed in the maganetic field, mechanical forced is experienced on the conductor, and the direction of the force is given by the Fleming's left hand rule and hence conductor moves in the direction of force.     F  = B I L                   where   F = force                                                        B = magnetic field strength W/m2                                                        I  = Current in Amp.                                                        L = length of conductor in meterQ2. What is the back emf ?A.  When the motor armature continues to rotate due to motot action the armature conductor cuts te magentic flux, and therefore emf are induced in them the direction of this induced emf is such that it oppose the applied voltage therefore this is called Back emf. .Q3. Why the DC motors are mostly gear motor ?A. Because the low speed motor are much more expensive than high speed motors of the same kW o/p rating.Q4. What is the suitable dc motor for electric traction ?A. DC series motor.Q5.  What is the suitable dc motor for vacuum cleaner ?A. DC series motor.Q6.  What is the suitable dc motor for paper making ?A.  DC cumulative compound motor.Q7. What is the suitable dc motor for shearing and punching ?A. DC cumulative compound motor.Q8. What will be the effect on the direction of rotation of dc motor if the supply terminal are reversed ?A. No effect because direction of the rotation changes when the direction of magnetic field changes.Q9. Why series motors are preferred for traction purpose ?A. due to large starting torque and slow down with the increase the load and automatically relieved from the heavy excessive load.Q10. How can the direction of the dc motor be determined ?A.	By applying Fleming's left hand rule .1. What is dynamo ?A.  A dynamo is the machine which convert either mechanical energy to electrical energy or vise versa.Q2. Can a generator produce electricity ?A. No, it can only creates a potential difference, which causes the flow the current. Q3. What is the essential parts of DC machine ?A. Field system, Armature, commutatore, Brushes, Armature winding, Bearings, Shafts.Q4. What is the function of commutator?A. The commutatore is the form of rotating switch placed b/w the armature and external circuit and so arrange that it reverses the the connection to the external circuit at the instant of each reversal of the current in the armature coil and thus convert induced alternating current in armature coil into direct current in the external load circuit.Q5. What is Armature reaction ?A. The effect of the magnetic field setup by the armature current on the distribution of flux under the main pole of the DC machine is known as the Armature reaction.Q6. What is the function of armature in the generator ?A.  It rotates the conductors in to uniform magnetic field and provide the path of very low reluctance to the magnetic flux.Q1. Where may Auto x-mer is used ?A. Auto x-mer are used when transformation ratio is nearly equel to unity and where is no objection to direct electrical connection b/w primary and secondry.Q2. What is the meant by by the rated burden of an instrument transformer ? A. The amount of power in VA which an instrument transformer handles at max. loading is called the rated burden of instrument transformer . Q3. Why the core of the transformer is laminated ?A. for reducing the eddy current losses. Q4. Why the excessive insulation is harmfull to a coil ?A. It makes heat transfer poor.Q5. What is the function of transformer oil ?A. transformer oil provides additional insulation, protects the insulation fro dirt and moisture and it carries away the heat generated in cores and coils.1. What type of load should be connected to the transformer for getting max voltage regulation ?A.  Inductive load .Q2. What type of load should be connected to the transformer for getting negative voltage regulation ?A. Highly capacitive . Q3. How the primary current increases as the current on the secondary side of the transformer is increases ?A. With increases the sec. current , sec. flux opposing the main flux increases, so the primary back emf E1 tens to fall, so diff. of applied voltage and back emf increases , therefore, more current is drawn from the source of supply flowing through the primary winding until original value of flux is obtained .Q4. Is the percentage of impedance of the transformer diff. on the primary or on the secondary side ? A. No.  percentage of impedance of the transformer is same on both sides.Q5. If the supply frequency is doubled, which loss component of transformer will double ?A.	Hysteresis loss component1.  Where the Buchholz Relay is used ?A. In the Transformer.Q2. Who govern the main role for the selection of the size of conductor in distribution system from the following    Corona losses,  temperature rise,  radio interference,  Voltage Drop?A.  Voltage drop.Q3.  What is the relation b/w the torque and o/p power in the DC separately excited motor when all the losses are neglected ? A.   Torque is directly proportional to o/p power.Q4. How the two transformers of different KVA rating working in parallel share the load in the proportional to their rating ?A.When their per unit leakage impedances on same KVA base are same .Q5.  How the inductance of the power transmission line increases?A.	It increases with increase in spacing b/w the phase conductors.Q1.What is stiffnes ?A. The synchronous torque is some time called stiffens of the generator.Q2.What is the relation b/w the pole, frequency and speed of motor/ alternator ? A.  Speed = 120* Frequency                         PoleQ3. Why Generator and Transformer rating in KVA but motor rating in KW ?A. Generator and Transformer rating Depends upon the power factor of the load but this is not specified at the time of manufacturing so rating in KVA while motor  rating of the is KW.Q4.  What is the principle of thermal power station ?A. We need mechanical power to run alternator and in the thermal power station  steam is produced by burnt coal in water tube and it energy user to run the alternator.Q5. Why speed control of motor is better by thyristor ?A.	Due to faster switching characteristics than other devices.1. What is the Principle of Generator ?A. The Principle of Generator is based on the Faraday Electromagnetic induction Principle, when there is a relative motion b/w a conductor and magnetic field, a emf induced in conductor and if the ckt is closed a current flows through the ckt.Q2. What is the Principle of DC motor ?A. When a current carrying conductor placed on the magnetic field it bears a magnetic force which is depend upon the magnitude of current and magnetic field and its direction is be perpendicular to both. Q3. What is Flaming Left hand rule ?and where it is used ?A. As shown in figueWhere             F = Force           B= Magnetic field           I= CurrentQ4. What is the Universal motor ?A.  Universal Motor can operate by both AC and DC Power-                                                                  Universal motor Q5. What things are constant of both winding in the Transformer ?A.   1. Power      2. Frequency





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