A quick cheat sheet on back emf in under 5 mins
ฝัง
- เผยแพร่เมื่อ 29 ก.ย. 2024
- A quick review on how spinning electric motors will generate a voltage that hinder its rate of turn.
See the longer explanation here - • back emf explained
Like what I do? Support by buying me a coffee - www.buymeacoffee.com/physicshigh
Subscribe - / physicshigh
For on going support, support me at Patreon: www.patreon.com/physicshigh
LIKE and SHARE with your peers. And please add a COMMENT to let me know I have helped you.
Physics High is committed to producing content that teaches physics concepts at a level a high schooler can understand.
See www.physicshigh.com for all my videos and other resources.
As well as this I produce a podcast series called Deep Impact - interviews with science communicators as to what they do, what drives them to communicate their craft
You will find these on the channel and also on podcast sites such as Spotify, Apple and Google podcasts
👥 Social
---------------------------------------------------------
Follow me on
facebook: @physicshigh
twitter: @physicshigh
Instagram: @physicshigh
I love this guy, his explanation is simple and easy to understand. Literally tutoring me 3 days before my hsc exam 😭
Glad it’s helping
@@PhysicsHigh due to Back EMF, does magnetic field strength of stator's electromagnet(DC motor) also reduced? Lets say stator required 1 amp to produce B=0.2T, but due to back emf if its only consume 0.5Amps, Does B=? also get reduced or its current consumption only effected and no effect on magnetic strength?
Here's a plan. As the rotor magnet sweeps through the stator coil field, producing forward EMF in the stator coil, harvest the back EMF by disruption, breaking the circuit at the 90° top dead center and you have what you refer to as high negative fleeting back voltage in the negative side. Since it is not accompanied by any current, it is useless qnd in fact problematic in the electrical industry. So, where is the current? It is still on the other side of the gap in the coil you created by the disruption, giving the motor / generator a real hard time. This is because of the time lag. You also have to harvest the back current. The reason we have this effect, is because the BEMF is merely 90° out of phase with the voltage and is locked out and prevented to get to the voltage, all though it wants to, but can't. You can wait till it jumps the gap, but then the voltage is too high and will damage your MOSFETs or othe devices you use to create the gap. Two things need to be done.
1) get the amps back across the disrupted gap
2) get the negative back amps in phase with the its negative voltage, which will create a powerfull negative EMF wich can be used in the most amazing way. And here's the solution, there's a name for it in fact, its called power factor correction. And I believe I have the perfect solution how to achieve this. And Im sure you caught on now as well .😊❤
energy (joules) is power-time (watt-seconds), not power (watts) in case anyone's wondering :P
exam in like 12 hours lets cram
how did you go???
Understood sir..
Watching this before my HSC exam ❤
nice
a lot of mambo jambo but still didn't explain it ....Oh well, on to the next video.
thank you for explaining why the current can't reach zero at operating speed. you're the only one who has explained it properly
Ok let me explain my question before I ask it please? Back EMFs are always explained as dangerous and bad for circuits, but can’t we use this back EMF to our advantage by storing the reverse charge then feeding it back into the circuit after inverting it?
I’m starting to wrap my head around circuitry, and want to explore what can be done with back EMFs.
There are no charge going in reverse direction. "Back emf" is simply a force, a breaking force on the current that is "moving forward" as per your power source. The faster the rotor is rotating, the stronger this breaking force becomes as it wants to make the electrons in the wore want to move in the opposite direction.
@@emf321 that’s the first time I’ve read it explained in this way. It actually makes more sense to me when thinking of Regenerative Braking.
This helped me so much. Thank you for the clear explanation
No mention of Lenz Law ?
left hand rule for motors and right hand rule for generators
Not necessarily. That’s if you use Fleming hand rule. But I’m not. I’m using palm rule. See my video on hand rules th-cam.com/video/GmURfG3tAhg/w-d-xo.htmlsi=uiZ_edD2vfwZP4Vg
actually I came here to understand, why the motor turns quicker, when the (permanent) magnets are given more and more distance??? 😢 Could you please tell me?
####!!Are you saying that the back EMF does not go through anode of Led, and is a negative flow of current? (not positive voltage)?...???
Sir the back emf has nothing to do w the supply voltage, sure if we do a kvl loop we can show how emf is equal to series resistance voltage drop + supply and also the emf will attempt to bring up this supply voltage…back emf is a function of the motor parameters such as Ke of motor and change rate of magnetic flux like you mentioned through the loop of wire..the statement that ‘emf cannot exceed supply voltage’ is simply not true as often times it does. If you are not to clamp a inductive load such as a relay for example w a anti parallel diode the relay coil generated voltage spike can certainly be above supply voltage and other components ratings damaging them…look into 4 motor quadrants, in quad 2 and 4 motor is a generator supplying a load to the ‘supply’ as current sinks to it as voltage is larger…also energy is not equal to VI…Power = Energy/time = VI….sorry good video otherwise..
This is so, so well made! Thank you so much! I hope you reach as many people as possible to help them all!
a moment of respect for this guy writing in reverse
Why low back emf causes the resistance reduced?
1:05 motor rotation direction by Fleming's left hand rule, not Fleming's right hand rule.
The rule I used was not Fleming’s rule
@@PhysicsHigh Thank you for clarifying. Your video really helped, appreciate it.
thought so had to double check as well
@@PhysicsHigh video Very well explained!! Just a doubt, if not Fleming right hand rule then which one?
but how you make it spin faster in the first place ? so that the rate of changing flux is higher ? you need to increase the current right ? then how does it become lower ?
You are increasing the current by increasing the applied voltage. What happens is that the current plateaus out - it does not increase at the same rate as the increase in applied voltage, due to the increasing back emf
Ok I was looking for Mitigation!
Thank You Sir ❤️ 😇 😊
Excellent new video format 👍
Thank u