Why should a series motor always start with a load?

In summary, a series motor should always start with a load because the current flowing through the motor will be high but the produced flux will be moderate. Starting the motor without a load can cause the speed to increase, leading to potential damage. On the other hand, a shunt motor can start without a load since the speed is not affected by the flux. However, it is important to use control and power electronics when starting a motor, especially in a train where high loads are involved.
  • #1
mahima
3
0
Why should a series motor always start with a load?
Why should a shunt motor always start without a load?
 
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  • #2
I'm pretty sure this is a homework question, so what do you think? By the way, there must be more to this question since it is not correct as written.
 
  • #3
In any DC motor the speed depends inversely on the flux. Consider when starting a series motor the current flowing will be high, but the flux that the motor produces will be moderate since the series winding has less number of turns. If u start the motor without load the speed will increase. as speed increases the back emf increases. this decreases the current through the series winding and hence flux decreases and the speed further increases. Theorerically speaking the speed becomes infinite. But practically the motor will accelerate to very high speed , which will damage the motor. But if you start the motor with the load, you are actually reducing the starting speed hence the motor runs safely. Since series motors has this property it is used in trains to pull high load.
 
  • #4
It is correct to say that a dc series motor can start at quite (even startlingly) high speeds, but don't you use any control? Are there no power electronics people on your railroad?

BTW, the OP was about series motors not specifically dc series.
 

What is a series motor?

A series motor is a type of electric motor where the field winding is connected in series with the armature winding. This means that the current flows through both the field and armature windings in a series, hence the name.

Why should a series motor always start with a load?

A series motor should always start with a load because it has a high starting torque and low starting current. This means that it is better equipped to handle the initial resistance of a load and can start smoothly without causing damage to the motor.

What happens if a series motor starts without a load?

If a series motor starts without a load, it can experience a phenomenon called "overspeeding". This is when the motor runs at a higher than normal speed and can cause damage to the motor or connected equipment.

Can a series motor be used for variable speed applications?

Yes, a series motor can be used for variable speed applications by using a variable resistance in the circuit. This allows for control of the motor's speed and torque. However, this method is not as efficient as using other types of motors designed specifically for variable speed applications.

What are some common uses for series motors?

Series motors are commonly used in applications where high starting torque is necessary, such as in electric trains, elevators, and hoists. They are also used in portable power tools and household appliances like mixers and blenders.

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