A quick cheat sheet on back emf in under 5 mins

  Рет қаралды 37,831

PhysicsHigh

PhysicsHigh

Жыл бұрын

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
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Пікірлер: 30
@jibraanrasheed7889
@jibraanrasheed7889 Жыл бұрын
I love this guy, his explanation is simple and easy to understand. Literally tutoring me 3 days before my hsc exam 😭
@PhysicsHigh
@PhysicsHigh Жыл бұрын
Glad it’s helping
@jxmiie172
@jxmiie172 8 ай бұрын
thank you for explaining why the current can't reach zero at operating speed. you're the only one who has explained it properly
@alex.e.jtulkens5283
@alex.e.jtulkens5283 Ай бұрын
This helped me so much. Thank you for the clear explanation
@spitfire5451
@spitfire5451 8 ай бұрын
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 .😊❤
@oyeha__uckya1223
@oyeha__uckya1223 5 ай бұрын
Thank You Sir ❤️ 😇 😊
@nuggetonastick1804
@nuggetonastick1804 Жыл бұрын
Excellent new video format 👍
@rockrocklobsterlobster6034
@rockrocklobsterlobster6034 Жыл бұрын
exam in like 12 hours lets cram
@samantharubinstein2699
@samantharubinstein2699 Жыл бұрын
how did you go???
@StudyWithCuriousExplorer
@StudyWithCuriousExplorer 4 ай бұрын
Understood sir..
@jimmybrad156
@jimmybrad156 Жыл бұрын
energy (joules) is power-time (watt-seconds), not power (watts) in case anyone's wondering :P
@siov4279
@siov4279 5 ай бұрын
Ok I was looking for Mitigation!
@waterfuel
@waterfuel Жыл бұрын
####!!Are you saying that the back EMF does not go through anode of Led, and is a negative flow of current? (not positive voltage)?...???
@pierrekhella8875
@pierrekhella8875 Жыл бұрын
Thank u
@fromisheon4867
@fromisheon4867 Жыл бұрын
Why low back emf causes the resistance reduced?
@jj74qformerlyjailbreak3
@jj74qformerlyjailbreak3 11 ай бұрын
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.
@emf321
@emf321 10 ай бұрын
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.
@jj74qformerlyjailbreak3
@jj74qformerlyjailbreak3 10 ай бұрын
@@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.
@thunchan14
@thunchan14 Жыл бұрын
1:05 motor rotation direction by Fleming's left hand rule, not Fleming's right hand rule.
@PhysicsHigh
@PhysicsHigh Жыл бұрын
The rule I used was not Fleming’s rule
@thunchan14
@thunchan14 Жыл бұрын
@@PhysicsHigh Thank you for clarifying. Your video really helped, appreciate it.
@MichaelSenior-uu7gx
@MichaelSenior-uu7gx 5 ай бұрын
thought so had to double check as well
@fadi5228
@fadi5228 6 ай бұрын
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 ?
@PhysicsHigh
@PhysicsHigh 6 ай бұрын
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
@Rospark
@Rospark 4 ай бұрын
Watching this before my HSC exam ❤
@pdfgovardhanb8093
@pdfgovardhanb8093 Жыл бұрын
nice
@concernkid
@concernkid 10 күн бұрын
left hand rule for motors and right hand rule for generators
@PhysicsHigh
@PhysicsHigh 10 күн бұрын
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 kzfaq.info/get/bejne/fdOFhcl4mNqlmJs.htmlsi=uiZ_edD2vfwZP4Vg
@paulwyleciol3459
@paulwyleciol3459 Жыл бұрын
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?
@yezan1001
@yezan1001 Жыл бұрын
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..
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