Back EMF of Motors: Constant or Variable?

[brainyman89]

i am wondering why in some problem they are regarding back emf of a motor as a constant value that characterizes the motor although current is sometimes variable? i guess the reason is for simplifying the problem, what do u think? can this occur in reality?

thanks for helping.

 

[Antiphon]

Constant motor rpm?

Can you give more information?

 

[brainyman89]

Constant motor rpm?

Can you give more information?

they are considering that E=Ir+E' where E'(the back emf) and r are constants although the motor is supplied by a coil that has previously stored energy. so i is not constant, it is decreasing to zero, however they considering that the motor functions normally as E>E', and E' is always constant to each motor.

Anyway, i think your justification that they are using "constant motor rpm" could work here.

 

[sophiecentaur]

Could it be that they are trying to make the problem easier?

 

[PJC01]

The back EMF of a motor can be both constant and variable, depending on the specific motor and its operating conditions. In some cases, it may be simplified as a constant value for the purpose of problem-solving, but in reality, it can vary based on factors such as the speed and load of the motor. This is because the back EMF is directly related to the motor's rotational speed and the strength of the magnetic field, which can change as the motor's operating conditions change. Therefore, it is important to consider the possibility of a variable back EMF in real-life applications. As a scientist, it is important to carefully analyze the specific motor and its operating conditions to accurately determine the back EMF and its impact on the motor's performance.