Right Answer is:
So DC motor provides high starting torque which is required to start a car.
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor's armature winding and restricts the current to an acceptable level.
The No Voltage Coil (NVC) is called NO-VOLT or UNDERVOLTAGE protection of the motor. Without this protection, the supply voltage might be restored with the handle in the RUN position. The full line voltage is directly applied to the armature. As a result, a large amount of current is generated.
Detailed Solution. If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.
A series wound DC motor like in the case of shunt wound DC motor or compound wound DC motor falls under the category of self-excited DC motors, and it gets its name from the fact that the field winding in this case is connected internally in series to the armature winding.
A series motor is a direct current motor that has two windings that are in series, with the same current flowing through each. Use of series motors is generally limited to cases where a heavy power demand is necessary to bring the machine up to speed, as in the case of certain elevator and hoist installations.
Series DC motors are a group of self-excited DC motors in which the field coil is connected in series to the armature winding and thus a higher current passes through it. A series DC motor mission is to turn the electrical energy into mechanical one based on electromagnetic law.
Series DC motors are generally used where high starting torque is required, and speed variations are possible. These types of direct connection motors are, for instance, used in the traction system, cranes, air compressors, vacuum cleaners, sewing machines, etc.
This can be seen from the speed-armature current and the speed-torque characteristics that on low armature current and low torque condition motor shows a tendency to rotate with dangerously high speed. This is the reason why series motor should never be started on light loads or no load conditions.
Which statement is correct about DC series motor? Explanation: When field winding is connected in series it has to be of made by thick wire. When field winding is connected in parallel it has to be of made by thin wire. So, thick wire is used with less number of turns while thin one is used with more number of turns.
Explanation: As soderberg line is the most safest line, the cost required to design according to this criteria will be more, followed by goodman line and gerber parabola.
Two pole motor has better efficiency. Two pole motor has better rpm and noise performance.
Explanation: There are 5 parts involved in the design of the machine. They are magnetic circuit, electric circuit, dielectric circuit, thermal circuit, mechanical parts.
10. What determines the output of a dc electric machine? Explanation: The dc electric machine output is the product of Total Magnetic loading, Total Electric loading, and speed in rps. Thus the output depends on total loadings.
The stacking factor (also lamination factor or space factor) is a measure used in electrical transformer design and some other electrical machines. It is the ratio of the effective cross-sectional area of the transformer core to the physical cross-sectional area of the transformer core.
The basic components of all electromagnetic apparatus are the field and armature windings supported by dielectric or insulation, cooling system and mechanical parts. Therefore, the factors for consideration in the design are, Magnetic circuit or the flux path: Should establish required amount of flux using minimum MMF.
Explanation: Factor of safety is defined as ratio of ultimate stress and working stress.
The first and most basic element of design is the line. In design, a line is any two connected points. These lines can be straight or curved, and may be smooth, rough, continuous, broken, thick, or thin.
Dated : 24-May-2022
Category : Education