Why series motor cannot be started on no load

It will not develop high starting torque 4. Asked by: Roselee Verdegay asked in category: General Last Updated: 29th March, Why dc series motor should not be started with no load? This is the reason why series motor should never be started on light loads or no load conditions.

At no load the armature current is very less and so is the flux, since the series winding has less number of turns. Which motor has highest no load speed? Thus, no load speed of DC series motor is highest. Which motor should not be started on no load?

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 DC series motor should never be started or Operated on light loads or No load conditions.

What is the main disadvantage of a series motor? With the increase in the load speed of the machine decreases, DC shunt motor maintains almost constant speed from no load to full load. With increase in the speed, torque of the dc series motor drops sharply.

What is the ideal no load speed for a series DC motor? With no load on the shaft free-running , the motor runs at the no-load speed NLS , the fastest possible speed for that voltage. When the shaft is fully loaded and not allowed to move, the speed is zero and the motor is producing its stall torque ST , the maximum possible torque. Answer: The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the armature rotates, is called back emf.

Its value depends upon the speed of rotation of the armature conductors. Why does DC series motor have high starting torque? As the armature current flows through the field winding, the flux produced in the motor is very high.

The torque of the DC series motor is proportional to the square of the armature current. That is why DC series motor has high starting torque. Again higher the load, higher will be the armature current and hence higher torque.

That's why DC series motor is suitable for pulling out heavier load. Which DC motor Cannot be started on no load? What happens if field is open in DC motor?

Answer: n d. In dc series motor the motor will go to infinite speed theoretically as flux is inversely proportional to the speed. What are the advantages of DC shunt motor? Advantages of DC Shunt Motors direct current machines can use for heavy industrial applications where torque and speed wider range. Shunt wound motor able to runs at a predetermined speed. The power supply of DC motor is any way cheap. What happens when DC motor is connected to AC supply?

When A. What will happen when DC shunt motor is started with load? Explanation: As the load will increase in rapid manner, speed change in DC shunt motor will be visible.

As load increase, speed will decrease, though by some small value. From, current armature characteristic armature current will be more than the earlier case.

Why does a DC motor sometimes spark on light load? DC motors as others motors have coil which are magnatized and the field produce interact with the other field of coil or Permanent magnet stator and thus produce torque and rotation. What is back EMF How is it created?

A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that's causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor. Now suppose the DC Series Motor is started at no load then DC Series Motor will take very small current from the supply mains as the input power needed is to only overcome the no load losses.

Therefore the no load current of DC Series Motor can be assumed approximately zero i. Therefore from equation 2 ,. In view of this, DC Series Motor shall always be started and operated under load mechanically coupled with it. If any query, please write in comment box. It will be my pleasure to answer. Thank you!