Three Ways To Run A Three Phase Motor On Single Phase, And the Pro's and Con's of Each Method #065

the first option I want to show you is the one that I think is best for most people it's going to give you the full power rating of your motor it requires the least amount of electrical knowledge and it gives you the most options as far as speed control using a potentiometer or other types of devices to control your motor and that is the single phase to three-phase VFD what you're looking at here is several examples of exactly that these two I purchased used on eBay this is the simplest one it doesn't have a digital interface it just has three plugs for the potentiometer this is a 5k potentiometer and you will need this to control the single-phase VFD this one right here is made by Toshiba and again looking at the label it says right here on the side source one pH which stands for single phase and then 200 to 230 volts almost always these guys are going to be rated for 230 240 volts this particular one is actually rated for 120 or 240 and it says that on their label which I will put on the screen for you right here it says 115 or 230 and there's actually a switch in there which allows you to switch between the two and then the VFD will take in 120 step it up to 240 and switch it to three-phase so this one is quite powerful as made by kb electronics and and I've used this one quite a bit and these other ones I have bought along the way these two were actually sent to me by supporters of this channel so thank you to my neighbors for sending these guys out to help me make more videos like this as you can see right here I am wired for 240 volts and this guy is plugged into this meter so that we can see how much power we are using okay a couple things about wiring these VFDs number one I'm going to go ahead and power this guy off so each one is going to have a slightly different configuration here but one of the things that you'll notice on pretty much every VFD is going to be there's a connection for Ras and T that's supposed to be your three-phase power in but most of but these guys that allow single-phase in will have you connect to just two of those in my experience most of the time that tells you to connect to ära and T but there are some examples like this one for example says connect to RNs I haven't actually tried it but I think it actually in the end it doesn't matter if you connect two of your lines to R and S or R NT but they give you instructions to just make them more concrete and then you'll also see which may be covered for you underneath the wires so let's look at this one and then you can see over here I've got you V and W and that's pretty much always the setup for your what leads that go out of your VF d and T your motor for this one again it's a similar kind of setup there's a connection for the ground wire which is right here and then that's probably pretty hard to see on camera but this one says UV and W and that one says l1 and l2 for your AC lines in over here you'll have three connection wires wannabe p1 p2 and p3 on the end and that'll be for your potentiometer now I don't want to go into too much detail about exactly how to wire these although hopefully that was pretty helpful but this at least gives you a good starting point but every VFD that you get will have a manual with wiring instructions inside so it's best of course to follow the instructions that they give you as far as how it should be grounded and where all the wires should go this is by far my favorite option but people are always looking for really cheap options so let me show you a cheaper alternative which of course has some limitations before I move on to the next method I want to show you there is one more thing I need to point out here and that is there are a lot of VF d's like this which take three-phase in and also put three-phase out and you don't want to mistakenly buy one of these guys okay so let me take a second to show you what you're looking for when you look at the label on the side there's almost always an input and an output and in this case it says three-phase input and three-phase output so again if you're in an American home this guy is not gonna work for you unless you have the last option and I'm going to show you and you want to control the speed through a more complex system again we'll come back to this but then you might use something like this so almost we'll put this to the side for now and let's put this one away this next method I'm going to show you is by far the simplest and cheapest but of course it's got several problems so let's explore that what we have here is a run capacitor and I want to distinguish this from Star capacitors which look like this they usually have a plastic body so they can be made cheaper these guys are only meant to have power cost them for just one or two seconds if you have this powered for more than that it will explode and you will see that any time you're working with capacitors I always have safety glasses on just in case because these guys will explode in a hurry and cause problems so this will be an example of a start capacitor and this will be a run capacitor this particular one is made for HVAC systems and so it's literally got two capacitors inside it says common here and then you see H erm and then fan if you connect to the common and the fan side you get the small capacitor which in this case is rated for seven is several micro farad's and if you connect to the common and the H erm side you're going to get the larger capacitor which is the 60 micro farad's so if you're curious about how that works now you know this one is oil-based and it can handle much more heat and that's why you want this application to use a run that are like this because it can stay connected in series with the motor winding and absorb all the heat from the power going through it another thing you want to catch is the voltage rating here this one is rated for 370 440 volts and it doesn't matter if the voltage is higher you just don't want one that's less than the operating voltage you're working at in this case this one is rated for 220 to 250 and we're actually going to use this here in a minute and it's fine for this application but the higher the better for voltage in terms of micro Ferentz we're going to get more into that in just a second so this guy is 60 micro farad's I have a wiring diagram that I'm going to show you when I get to the more complex setup there of this but this is the most basic set up I've got my power coming in here is my ground which is connected to the body of the motor on the inside here is in this case both of these lines are live even though this one is white these are the two sides of the 120 and here in the u.s. they're 180 degrees apart electrically speaking which gives you 240 volts so that's how you go from 120 to 240 and in this case I've got 240 coming in on this line okay so I've got both lines broken at this switch and after going through the switch I've got my l1 which is this guy here we're just going to call it l1 is connected directly to power the other side is also going through the switch and then through the capacitor to l2 we're gonna call block l2 and then l3 is just connected to the common side of the power coming in and again I'm going to show you a wiring diagram here in just a moment alright so I decided to switch motors because this one's a little bit quieter without the gearbox on it but the wiring is basically the same the only thing I want to point out is you'll see that there are more wires here these two blue wires are for thermal protection and so we won't be using those too because we just don't need it for this temporary application these three represent my l1 l2 and l3 and the green wire is my ground wire but that's not always the case I have another motor just like this one that I took out of a treadmill this one also comes out of a treadmill a commercial treadmill which is wise three-phase you don't normally see that in the home variety type but anyway sometimes this wire is purple and so you can't rely too much on the color I just wanted to clarify that green is not always the ground wire so anyway we now know this is l1 l2 and o3 we've got my capacitor wired up just like I just showed you a moment ago so let's fire it up and see what we get [Laughter] now when you're using just one capacitor as you saw at the motor is extremely weak we should be getting about 1700 rpm and that looked to be closer to maybe 80 or so so it doesn't quite have the starting torque to get all the way up to speed so we need more capacitance in this case I've only got 60 micro farad's and this is a run capacitor I'm going to show you a better technique here in a moment but we're going to start by just adding another run capacitor so we're gonna put this guy in parallel so you're gonna essentially connect the same common to common and so on and this will effectively give us 120 micro farad's would run capacitor so there are a couple things that I want to point out while I'm thinking about it number one we are indeed still running a three-phase motor on single-phase and so the horsepower rating for this is really only about one third of what you would get out of this motor when it's part properly and that is comparing this method to running this guy on true three-phase that's because we've really only got single-phase power coming in we have tricked the motor into thinking that there's a second phase there by using the capacitors to shift the current in these in another winding but that's not actually enough to give the motor its full power rating and running the motor like this you're gonna have an unbalanced load which is what you just saw there the current across one of the windings I think was 12 and I don't remember the exact numbers but I think I had two and twelve on one I'll just put the numbers on the screen but I want you to see how widespread the current is across the three lines that's really hard on the motor and that's why I don't recommend doing it this way but I have seen YouTube videos where people have done this so let's improve this set up a little bit and then I'll show you one more setup that I think is much better than this option okay so I almost forgot to mention something really important and that is when you run the motor with an unbalanced load it produces some heat and the motor was starting to overheat so I'll set the fan on it for a little while to kind of accelerate the cooling so that I could continue shooting but that brings up another important thing is that you can't do this for long periods of time with this type of setup if you're gonna be running say a three-phase motor on your drill press where it starts with zero load there's a heavy load for 30 seconds or so and then there's no load again this might be a good application but if you working on a lathe and maybe you're gonna be cutting for long periods of time I would suggest you don't use this capacitor run method because in the long run that's gonna be damaging to your motor from what I've read online this is kind of a dark science there is no hard and fast rule you need about 60 to 75 micro farad's per horsepower this is a four horsepower motor so I just don't have enough capacitors in order to balance this load out I thought I might try with what I had here in the shop I actually purchased these two specifically for this project and then when I went and looked at my basket I see I actually didn't have any more on hand so this is all I have for this experiment so now that you understand this I want to show you some ways that you can improve this system for one we still have very weak starting torque now I told you earlier that start capacitors have a high capacitance but they can't be in the circuit for very long this guy can only be wired for about a second or so but looking at the label you can see this can put out a 126 micro farad's for about one or two seconds but if you leave it power longer than that it will explode and we don't want that so how can we connect this guy temporarily to the circuit well one option will be to use a momentary switch which is actually something I recommended in a video a long time ago you could wire this capacitor with a momentary switch and what you would do is flip on the circuit hit the momentary switch that would start the motor and when you let go it would disconnect the start capacitor but I recently discovered a device that does that for you automatically and that is the potential relay this is so cool I didn't even know this existed a month ago but now I have another device that is very ingenious and I'm going to be using these guys on future projects so let's talk about how this guy is wired up now between number 1 and 2 we have a normally closed circuit it means when it's just static like this I have continuity between 1 and 2 and if I had something connected across this guy it will be powered so let's just set this to measure continuity and you can hear from the audible chirp there that 1 & 2 is a closed circuit now so power run between 1 & 2 but there's actually a coil between 2 & 5 as well and if I try to measure continuity there though you hear that there's no beep electricity can't flow in that direction if I set this to measure ohms I can see that it's measuring about 18 mega ohms so there's definitely a connection there but the resistance is really high and that's because there's a coil there that can open the circuit between 1 & 2 now I'm gonna put the wiring diagram on the screen so that you can see it but this is basically what happens when the motor starts when I flip the switch on I've got power across both my start capacitor all the other capacitors and the motor but once the motor actually gets up to speed it start producing its own electricity just like a generator and it's trying to push some current back through the system in fact we call that back EMF that back EMF is powerful enough to push current across 2 & 5 and when it does that that actually opens the circuit between 1 & 2 it's just really genius I love this guy as long as I have back EMF across 2 & 5 1 & 2 will be open and this guy won't have power across it so that way your capacitor doesn't explode and you get a good kick at the beginning for the starting torque that you need so let me hook that up for you just so that you can actually see that it works and the capacitor doesn't explode all right I've got my potential relay wired up here and again this looks kind of messy but everything is in the wiring diagram and you can see where there's a bubble the wires are connected and where there's a line or half loop you know those wires are not connected the thing I want you to see is that this capacitor is basically in parallel with the other two capacitors except number five is hooked back to the same side as number one in this case I've got my safety glasses on just in case I'm even going to turn this guy that way I'm just kidding I'm not worried about it oh one other thing I want you to notice is you're gonna hear kind of a rumbling sound it's almost like an egg timer but it's kind of subtle you may not hear it over the motor actually but that's this guy with the coil pulling the magnet up which is opening that circuit so hopefully you can hear it so I let it run for a few seconds and I've got stuff vibrating all over the workbench here but there you go hopefully you could hear that rumbling kind of egg timer sound from this that sound indicates that it's working properly and that it opened up that circuit so that's method number two again this is my least favorite actually man it's getting warm again already I've only run it a couple times I mentioned this before but it's worth saying again I would only do this type of setup you know in a case where I had a motor that was much larger than what I needed this is a great example because I got this from a treadmill that was abandoned behind a gym the gym had closed this is a commercial treadmill got the motor out of it it's full horsepower but I've got many applications where I only need 1/3 of that so this is a great example of a motor that's larger than I need and if I if I need it the cost to be as low as what you see here then you could do something like that but definitely if you want to get the full capacity of the motor you should use a VFD or the next method I'm going to show you now [Music] this method is by far the best if and only if you want to run multiple motors in your shop this can indeed cost just as much as purchasing of VFD if you only want to run one motor on three-phase then I suggest you get a VFD that to me is the best option but if you want to run your whole shop on three-phase then you need to do this setup this is basically called a rotary phase converter it's where you use a three-phase motor powered with capacitors and single-phase input this motor remembering that back EMF I told you about will actually push the third phase back out into the system and so this motor is essentially wired in parallel with this one and as long as I let this guy idle and I have enough supply voltage coming in from my single phase then I can run actually more horsepower on this system than my pony motor up to three or four times as much if you have multiple motors running and you don't try to start them all at the same time you still have the issue of trying to start your three-phase motors and so if you've got your capacitor set up and you run one motor at a time you would just simply start your pony motor which is what this one will be called you start that guy first it can be set up in another room if you need it to be quieter and then you just run in parallel alone into your shop it could go to a panel which would be like your three-phase panel from there you will plug in all you are the motors in this case that's what I have here this motor is wired in parallel with this one and that's gonna give me three-phase a much smoother three-phase power to these motors that are out in the shop and with this setup assuming that you've balanced everything with your capacitors which as I explained earlier I don't quite have that here you could run this guy at its full rated power so this to me is the best method again if you want to run multiple motors from your shop and sort of have three-phase supply for your whole shop and finally you could still have one or several of your motors power by VFD and you could actually use a cheaper one in this case because now you've got three-phase supply you me one that goes from single-phase or three-phase which sometimes cost a little bit more this particular model is rated for one horsepower with three-phase input and again if you wanted to do that kind of setup this would be a good option for you I'll show you the wiring diagram there are a couple more things that need to point out about wiring that's worth mentioning here number one every state in fact every county in every country has its own wiring code it's important that you double check with your local wiring codes and just make sure that what you do is in compliance with the region you live in I also want to say that I am certainly capable of making mistakes I don't consider myself to be an expert just a guy who loves to tinker with this kind of stuff so if I figure out after posting this video that I've made a mistake I will add notes to the description so please be sure to look at the description so that you can see any Corrections that you need to make before you try to copy anything that you've seen here if you found this video helpful be sure to let me know by leaving me a comment and giving the video a thumbs up thanks for watching [Music]

Channel: Jeremy Fielding

Views: 630,243

Keywords: three phase motors, three phase on single phase, rotary phase converter, variable frequency drive, VFD

Id: cE34YHsRY88

Length: 22min 53sec (1373 seconds)

Published: Mon Sep 10 2018