Back EMF help (1 Viewer)

[somethingman30]

Could someone please explain the whole concept of back EMF. I know it rises as a result of Lenz's law and the law of conservation of energy, but I'm now sure how to explain it in detail.

Also, I know that back EMF opposes supply, but what are the states and why does back EMF initially oppose, but then slow down. (Not sure about this but I remember reading it somewhere)

Sorry for the ambiguity, but this concept is really confusing to me. If you are confused, just explain the entire concept in full detail please.

Thanks

 

[atargainz]

pretty much:

Lenz's law states that a relative movement of a conductor in a magnetic field induces an EMF that creates a magnetic field opposing the initial change in flux. (formula) This is consistent with the conservation of energy as the induced current acts against the movement of the conductor, slowing it down. If this were not true, then a constant force will be provided by the induced EMF, accelerating the conductor without bound, and thus, violating the conservation of energy.

Back EMF in motors is created due to the movement of the coils(rotor) in the magnetic field (stator). This causes a change in flux, that according to Lenz's law, produces an induced EMF in the coil, that acts against the initial current, effectively negating part of it. This means that as the motor speeds up (rate of change in flux increases), the back EMF will increase, whilst supplied current decreases. In an ideal motor where there is no friction, back EMF = current as the motor approaches maximum speed. This is beneficial as it reduces the likelihood of a motor 'burning out'.

 

[somethingman30]

pretty much:

Thanks a ton.