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How is torque produced in a dc motor?
torque = force x Radius of the armature
Why DC suuply used in Excitation of Alternator?
for torque improvement in armature and create n-pole or s-pole in armature a dc source is used in alternator armature.
Operation of DC generator?
1) PRINCIPLE:Whenever a conductor cuts magnetic flux, dynamically induced emf is produced in it. ( Faraday's Laws of Electromagnetic Induction ). This emf causes a current to flow if the conductor circuit is closed.2 ) OPERATION:Field winding produces magnetic field in D.C. generator. Armature is coupled to the prime mover. Prime mover produces torque so the armature rotates. The armature cuts the magnetic field so the emf is induced in the armature. When load is connected to the armature, electric current flows from the armature conductors, through load and back to the armature conductors. Now, as current flows through the armature and it is in the magnetic field, torque is produced due to it. (This torque is called back torque). If the load on the generator is increased, the back torque increases so the torque of the prime mover also increases and the input power to the prime mover increases. In this way, the generator converts mechanical energy into electrical energy.It should be observed that the emf induced in D.C. generator, is A.C. ( so the emf induced in the armature is alternating in nature. ). Then with the help of commutator, it is converted into D.C. Rings and brushes are used to take the emf outside.
Why the induction motor does not have armature reaction?
Because the armature (or rotor) has no external connection. The currents that produce torque from the rotor are induced by the magnetic field in the machine, so there is no commutator, no brushes and no armature reaction.
How will the armature current and the output power of a dc shunt motors change with increasing load?
With increasing torque load the armature tends to slow down; the motor draws more current to compensate, and if there is armature resistance the back emf generated by the armature falls to allow the increased current to flow, which causes the motor to settle at a lower speed. The mechanical output power is the speed times the torque, and increasing the torque increases the power output provided the speed does not drop much.
Would a DC motor turn if only the armature were supplied DC voltage?
if there are magnets on the stator and the commutator is phased properly this is known as a permanent magnet dc motor the starting torque is dependent on armature current and the strength of the magnet the speed is directly proportional to the armature voltage a shunt motor needs the field energized for starting. more field more starting torque
What role does the armature do in a DC motor?
One of the role of the armature in the DC motor is to carry the current that is crossing the field. By carrying the current crossing the field, it creates the shaft torque in the rotating machine.
How can i control the torque of the wiper motor?
there three connections of armature circuit possible in wiper motors. by changing these arrangments, we can control the speed as well as the torque of any wiper motor.
What is shunt and series motor?
A series motor is one in which the field windings are in series with the armature windings. So the torque is proportional to the square of the supply current.'Shunt' is an archaic term for 'parallel'. So a shunt motor is one in which the field winding is in parallel with the armature windings. So the torque is proportional to the supply current.
Why it is an advantage for armature to rotate in radial magnetic field rather than uniform?
1.maximum torque is experienced 2.torque is uniform for all positions of coil
What is the Significance of back emf in dc motor?
Fig. (4.3)ZN/60 A) is large and hence the motor will draw less armature current and vice-versa.4.4 Significance of Back E.M.F.The presence of back e.m.f. makes the d.c. motor a self-regulating machine i.e.,it makes the motor to draw as much armature current as is just sufficient todevelop the torque required by the load.Armature current,abaREVI−=(i) When the motor is running on no load, small torque is required toovercome the friction and windage losses. Therefore, the armaturecurrent Iais small and the back e.m.f. is nearly equal to the appliedvoltage.(ii) If the motor is suddenly loaded, the first effect is to cause the armature toslow down. Therefore, the speed at which the armature conductors movethrough the field is reduced and hence the back e.m.f. Ebfalls. Thedecreased back e.m.f. allows a larger current to flow through thearmature and larger current means increased driving torque. Thus, thedriving torque increases as the motor slows down. The motor will stopslowing down when the armature current is just sufficient to produce theincreased torque required by the load.(iii) If the load on the motor is decreased, the driving torque is momentarilyin excess of the requirement so that armature is accelerated. As thearmature speed increases, the back e.m.f. Ebalso increases and causesthe armature current Iato decrease. The motor will stop acceleratingwhen the armature current is just sufficient to produce the reduced torquerequired by the load.It follows, therefore, that back e.m.f. in a d.c. motor regulates the flow of armature current i.e., it automatically changes the armature current to meet theload requirement
4 Plugging of DC motor is normally executed by?
In case of 1phase the reverse torque is obtained by reversing the current either in armature or field
