500 An Induction Motor As A Generator Without Altering The Motor

[Music] hi so we've been looking in previous videos at our electric motors in particular configuring those motors to be generated so we've been looking at this kind of thing this one is a motor from a printer then you can see it in a ring magnet in there and that in this case that's the stator and then we've got the sorry that's the rotor then we've got this thing here lots of calls whine arounds basically electromagnet that's the state so that's the rotor they fit together like that this is held flat you pass a current through that and that will rotate and obviously if we do the opposite of that we rotate that then we can get a current out of that by the induced current of the magnetic field lines cutting the coils so that is the kind of motor that we've been looking at now it doesn't represent the most popular kind of motor the most popular kind of motor etches the induction motor and here's one I took from a drill actually now I take that to pieces then you look at the inside of it here we've got the rotor that casts and the stator in this case it looks very similar to the ones we've got in that we can pass a current down here to create a magnetic field in this data and then we pass an opposite current using the brushes and the commutator just there to pass the field on there creating another electromagnet so instead of using permanent magnets we use two electromagnets to do essentially the same job to the requirements of that obviously is commutation from these ones then we can actually use electronic commutation so they're brushless motors these ones they have these little brushes in them making them a brushed motor so that one actually I think is relatively easy to understand you we know what's going on there create an electromagnet and we can create electromagnet by passing a current but equally they are not particularly popular in that style because it uses brushes and those brushes wear out what do you find an awful lot of is this kind of motor this one I actually took from I think never take that to pieces it's going to look something similar to the electric motor that we just looked at but it's got something really weird in it that kind of makes it difficult to understand and I think it's because it's difficult to understand that you find a lot of DIY projects using variants of this kind of motor and very very few indeed using variants of this kind of motor and most of the projects what they do is drill the motor out and put magnets in to effectively make this into this that's what they try to do if I take that out well seize there is our stator and it's as we expect it's a couple of field coils and we generate a magnetic field with that by passing an alternative current down it so that we understand the really weird one is this this actually has no connection at all it doesn't have brushes it has no coils on it and yet when we pass a current down there that will rotate then there that's a mystery what why that actually works is is really really mysterious and I think it's one of the reasons so what people are we doing with this is drilling holes in it and blue magnets in and then when you can spin that you can make that into a generator like that if we just put that in there and spin it because there's no magnetic force on there then it won't do anything it won't generate and I guess that's why people are gluing magnets to it or they replace the entire thing with it another magnet that these kind of motors which are induction motors as well are absolutely fascinating now I've got a even bigger one here I can see a little bit better and this I took from a wet grinder and we pull that to pieces status' I expect there's a whole lot of coins in there no surprise there at all and here is the rota now if you look on that rotor you can see little lines going down on that rotor in this packed shell this shell is made of a thin laminations of steel and those lines are actually electrically conductive with each other and joined up in loops so they're shorted at the ends here so all of these lines are effectively little circuits now what happens is when you put a current in here then the field will induce a current in here now if you only use things with air see because we let that alternate current drop then that field will drop and this field here will also drop and that will induce a current so the magnets if you like electromagnets themselves are self-contained in this tiny little circuit in the rotor and that kind of fluxed me four edges so I think you certainly think that foxes people but there is no way of making a connection to that and the connection isn't needed because when that feel and that current stops it will also generate its own collapsing magnetic field now that's really curious when you think about it that we're inducing a field with an actual contact it's very similar to how a transformer works now a transformer can have a gap between one part of the transformer and the other as long as they're close enough they will magnetically couple and putting an AC current down on one side will produce an AC current on the other side of the transformer even if there's a tiny gap there but sometimes they put a gap in deliberately and that's things like flyback transformers so effectively it's a kind of transformer with a very small circuit and these lines are in fact this circuit now if I were to do that then just like the flip transformer it won't move because there's no actual force on it what I need to do is get that field to rotate in here and I can do that if I use not in a current so as that alternate current drops down again if I start another alternate current 90 degrees out of step of that first off current then I will get a force on this because of the time like difference and that's difference in force will in fact lead to rotation in this that's very cool now you often find these thing things in three-phase AC because the AC feed has given you that rise and fall in steps of 120 degrees and that will create the force on that and just spin that magnets but you also find these in single-phase to have a single-phase of these what you need to do is and lapse the field by at least 90 degrees and you can do that just by putting a capacitor on one so this one that easily has two sets of windings it has a primary winding where the main phase is going in and then what's called an auxiliary winding where the capacitor feeds it and it's in the auxiliary winding that you get that starting motion because a phased motor like this will actually turn if I start it by hand so I just feed that phase and give it a spin it'll continue to spin if I put the ancillary winding in there it makes itself starting so there's a single phase induction motor now equally there is nothing on that adds on that rotor at the moment so if I spin that I'm not going to get a current out of it I have to do something to get a current out of it and again people been drilling holes in it and gluing magnets on but actually you don't need to you can do this just by using a couple of capacitors and I've got a couple here these are microwave oven the transformer capacitors incidentally there are about in micro farad each and they're a couple of thousand volts in order to make this work properly you need a couple of hundred default capacitors about 400 volts because this one's actually 240 volt motor about 400 volts and about a hundred two hundred microfarad something like that so you'd need it quite a few of those but get it working with this which is what we're going to actually do now this motors really counter call because it tells you how many diaphragm how to actually connect these things so this capacitor that I'm putting on at the moment is the one that will feed the of jewelry wand in creating that 90 degree out of phase step here are my main power this used to go into the mains if I connect that up to the multimeter I'll get absolutely nothing even a spin map because there's just no magnetic field however if I connect that I'm looking for cable so we got if I connect that with the capacitor there is enough residual magnetism in that router to start a tiny tiny charge and that charge will build up and be stored in the capacitor and then that stored charge will create a magnetic field within the rotor and then it will build up and actually generate which i think is super super cool there are a couple of limitations with this incidentally because that field has a specific time that it rises and falls for us obviously it's 50 to 50 Hertz here in the Europe I think it's 60 Hertz in the US you might be the other way around but there's a fixed time that these things work and there has to be a lag between the rotor and the stator and that lags called the slip and that gives a force on it that will turn it and it's really rated at a fixed speed so they tend to be about 1415 1800 rpm when you run them at that then they're absolutely incredible motors they are in fact the motor that you find in in electric vehicles at the moment for obvious reasons they're cheap and robust and they don't use magnets they find them a lot in thirst kind of things as a generator which is what we're bringing up here incidentally as a generator then we have a limitation on speed just like we have a speed limitation now there are ways of varying that called variable frequency drives for a motor for a generator it will be a motor as long as it has that positive slip that is it spins at less than are up to its rates and spinning speed let's say fifteen hundred every preserve fifty Hertz if we spend that fifteen fifty or fifteen sixty then it has a negative slip and the reverse happens it actually becomes a generator so we can make that a generator if we feed a current into the device prior to getting it up to speed now that might seem like a hell of a lot of things to do in order to get that to generate but the current you need to feed in is tiny compared to the currently you get out because you're adding in the motion of the rotation by the load that you're putting on this now it is also self leveling it won't exceed its load it can only get up to a certain amount and then it just doesn't get any higher so a self-protective which is great when you think about a wind turbine for example where you got that variability new is too fast you can blow your motor you electronics here you can't do that like I said the amount you have to put in is very very tiny and that's the point of it connecting the capacitor in line with the actual motor output is initially with that in residual magnetism then we will get magnetization of that rotor that will feed back into here to or feed back into there and continue that build up until there's an excess and then an excess we can draw off as actual power under load so to demonstrate that obviously I've just connected the whole thing off what I'm going to do is give you a close-up of that and spin that motor okay so I'm just gonna spin this by hand and there's the voltage reading there it's an AC output incidentally then I just give that a little spin then just by twiddling that with my fingers which really is not the best I can get that up to about a vault of output okay so that's quite a bit of fun um it is actually tremendously easy to turn one of these won't motors it's called a squirrel cage incidentally and when it's like that that's a squirrel cage rotor another term one of the squirrel cage inductor motors into a generator it's actually really really easy I don't have to go around drilling holes and gluing magnets onto the thing all you have to do is put a capacitor in parallel with the motor when you do that it becomes self-starting and a generator that's actually very very cool not to know what kind of capacitance you put in there I don't really know all I did was stick capacitors on there until it actually worked no buds it worked I was happy I guess is aware of calculating you'd have no idea hopefully somebody can post that for me that would be awesome if there was a post on that it is limited by speed you do have to get it above that ratted speed so it's rated at 1500 then you do have to get it around about 1550 1600 and then it's actually a really good generator but even spinning that by hand or the capacitor in parallel with it then we can get a few volts out of it and if we get that at the right speed actually there's a dramatic change as there's this point at which the torque curve becomes incredibly stable and so you can put a load on it at that stage you ever spinning it by hand if we put a lid on we would just kill it if we get it up to speed him again on that point of the talk of we can actually put a very high load on that and it will continue to generate and feed back into it without you having to drill things out and glue magnets in so there we go hope that was of interest but that's how to convert a squirrel cage induction motor into a generator stick in a capacitor on I hope that was of interest and thank you very much for watching

Channel: Robert Murray-Smith

Views: 104,178

Rating: 4.8932147 out of 5

Keywords: induction generator, fwg, robert, induction, motor, generator, murray-smith, design, technology, science, fair, project, off-grid, electricity, generation, power, alternative, engine, disruptive, d-i-y, diy, make, made, build, built, home, how to

Id: j-LgEbdJ8AM

Length: 15min 10sec (910 seconds)

Published: Tue Apr 14 2020