back emf explained

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Back emf is a situation called self inductance and occurs in electrical motors. It results in power loss that is unavoidable, since it is a result of physics principles.
This video covers the basic of why it occurs.
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Опубликовано:

20 окт 2016

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Комментарии : 173

@Fearofthemonster 7 лет назад

Suggestion for the future videos. Whenever you are talking about a hand rule, add a small picture that shows how the hand rule is supposed to work.

@chetankg8475 5 лет назад

The direction of rotation is wrong.

@mindiyasara 6 лет назад

You mixed up Fleming's rules but thank you!

@jme2006 Год назад

your hand rule at the beginning is also wrong. When talking about motors, you use the LEFT hand rule, not the right. This is why it's so important to have a physical hand diagram right there.

@marktamereal8337 7 лет назад

Finally someone with an Aussie accent that doesn't speak at 300 words/second

@karilentz5000 5 лет назад

Without back emf, all the electrical power will go to heat dissipation and the mechanical torque would be a free lunch. Back emf comes from energy being conserved, it lowers the armature current, making it look like there is an extra resistor, but instead of dissipating power through heat like a real resistor, the dissipated power the shows up in the torque.

@TheHyderabadiChronicles 5 лет назад

You're voice is like iron man.

@fransmurati2370 2 года назад

The pointer is hardly noticeable, rather confusing when you speak about this wire this wire, a bigger and perhaps yellow pointer would have helped

@michaelpilks

Thank you so much, my physics exam is tomorrow and my useless physics teacher didn't cover this, you're a life saver

@tomloucaides264 5 лет назад

Someone doesn’t know his left and right.

@coreanoquant 5 лет назад

Other than getting the right hand and the left hand mixed up, probably the best explanation video on RU-vid.

@maherfatfat2835 4 года назад

Great explanation, especially at the end when you mention why there is a special circuit designed to protect the motor from burning (to absorb the spike in current due to the sudden absence of back EMF when the load is suddenly disconnected)

@calholli

That's also why motors have such a huge current spike when they first start.. Because at first the full voltage is essentially back EMF since there is zero movement-- but once the movement starts, the current will drop proportionally to the RPM. On larger motors, the inertia is so great that the current spike has so much back EMF that the motor can't even start... I'm assuming that's why they will require a 'starter capacitor".. such as in HVAC motors.. which use a "run capacitor and a second "starter capacitor. (I could be wrong about that. :)

@ToddBeal 2 года назад

Thanks for the explanation on the relationship between back EMF and flyback voltage spike.

@jimcar53 6 лет назад

thanks so much for this explanation.

@ameliachen4297 6 лет назад

This really helped! Thanks :)

@denisranque1536 7 лет назад

Thank you for the clear explanation !!!

@georgeb6909 2 года назад

Great explanation thank you!

@kaunainajaz4436 5 лет назад

Awesome explanation.

@Yureka-ox5jn 3 года назад

I think the voltage that face resistance (as you said back emf) is like drain of voltage which gets stored in the form of magnetic energy and released when input voltage is going down (forward emf)