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Forum Index : Other Stuff : PM motor as generator
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| jazzman Newbie  Joined: 29/01/2010 Location: Posts: 11 |
Hello all, new to the forum. I am working on a project that would hopefully get me some ac power out. I would like to use an AC motor as a primary mover to spin 1 or more PM motors to generate 12 volts DC to charge batteries which would then be used to provide DC to inverters. My question is will PM DC motors generate a signal that is damaging to an inverter and if so, how can I clean it up. I have looked into using charge controllers but cannot find any info on this. Any help is appreciated. |
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Greenbelt Guru  Joined: 11/01/2009 Location: United StatesPosts: 566 |
Jazzman; You would be miles ahead and money in your pocket to buy a standard battery charger. If this is portable power you need, just charge the Batt's and haul them to your inverter. Time has proven that I am blind to the Obvious, some of the above may be True? |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
If you already have a.c., why manufacture d.c. and turn it back into a.c. using an inverter? Maybe a more fine-tuned explanation of what you are trying to accomplish would be in line here. After knowing your end game, perhaps some of us can help you along your journey. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
Thanks for your replies; I will explain myself as best as I can. Basically I am trying to generate AC power.By using a primary mover,in my case I am using an AC motor of about 1 hp, 115vac single phase. This motor will spin at about 1100rpm and up to 1725rpm. This AC motor will spin a PM 12VDC motor which will be used to charge batteries. I will use a charge controller to maintain/charge my batteries. These batteries will connect to an inverter which will then power my loads.One of my loads will be the Primary mover AC motor, any extra power I can get from my inverter will be basically (At least to me free energy). All this is just the beginning stages as I have plenty of ac/dc motors. I am sure there are many ways to do this, you could imagine it as a windmill project but instead of using a windmill generator to produce power I am using pm dc motors to continuously provide power to batteries which are generated by way of the primary mover AC motor. My concern is that I connected an iverter to my battery which was connected to a pm dc motor as generator and it blew it up. I guess the dc motors frequency is to high for the inverter. The problem though is that I was using a an APC UPS.As I have several of these. This of course is just a test. By the way, I have run these APC UPS's for several hours under halogen lights and they run great. They are built tough and if I blow one just because it can't handle it then that's ok. I have other inverters that I can use but am concerned about the pm DC motors as generators are causing noise of some kind and killing my inverter. Thanks for your replies hope this helps. |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
Hi Jazzman What you are trying to do is called over-unity. Its not possible, and you will understand that once you know a few laws of physics. Put simply, you get less out than you put in. Thats law. Your big AC motor might be about 80% efficient, so if you feed in 1000 watts ( watt is the measurement of energy we commonly use ) of AC power, you will get out 800 watts of mechanical power. Feed this 800 watts of mechanical power into you DC motor/generator, and you might get 600 watts out in the form of DC electricity. These are real figures here, you cant get over 100% effiency, you ALWAYS get less out than you put in. Now say we bypass the batteries all together for the sake of simplicity, and feed this 600 watts of DC power into our inverter, then we might get 500 watts out in the form of AC power. So at the end of the chain we have 500 watts of AC power. We fed in 1000 watts of AC power. Our big old motor needs 1000 watts to run. End story, it wont work. Hope that makes sense. Its a common idea, lots of people have tried it, but it cant work. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Do you know something that the rest of us dont know? Like how to get more energy out than what you put in? I think your losses are to big along the way for this to work. You will not end up with free power as you will take more out of your batteries than you put back in. If it did work the rest of us would have gone this way long ago and not built windmills instead. Pete. Sometimes it just works |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
I somewhat get it.So what you are saying is if I have 800 watts of mechanical power that there is no way I can get over 100% output no matter what combination of motors/generators etc. that I use.I ask this because there are so many options out there such as using ac motors as generators and even very low current motors by Baldor.Im sure there is no simple way of calculating this as there are many variables.One thing that has me thinking is, if 2 or more ways of generating power are not equal (1 being more effecient than the other) then would not one asume that more power can be output than what is input.If not then where is the difference going.So what if one uses a flywheel system. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Ask yourself this. If it was a workable system than wouldnt every power company throughout the world shut down their coal burning and reactors and adopt this theroy long ago. They have budgets of billions to research these things and they dont work. You can belive Utube if you want. Build a pedal generator and see how much energy you loose to create 1Kw. with or without a flywheel. Anywhere in a electrical circuit you can feel heat is a loss of energy to start with. As Glenn said nothing is 100% efficient, so you have a loss at every stage. Its like pouring water down a leaky pipe, you will still get water out the end but just less than you poured in. And no you cant plug the leaks. Try if you wish and prove us all wrong or right we wont mind, as its your time and money being wasted. Pete. Sometimes it just works |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
I don't particularly care about power company's, powering the world etc. Obviously there is no perfect system.This is just about making a little power so as not to have to drain my wallet.I see a windmill generator next to your 3 stars so I guess you must believe in something. I was hoping to get some help with my initial post but looks like I stumbled into the white house. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
Hi Jazzman Please dont get offended, its just this sort of thing popps up a few times a year. Its like if I posted a message to say I'm going to teach my dog to speak Latin. Now I figure my dog has a brain, its aware and smart, so why can I teach it Latin! Everyone will tell me it wont work and to stop wasting my time. But I'm not convinced, and still think I should be able to teach my dog Latin, so try to argue my case. Pretty soon I get annoyed with everyone for not wanting to help me. I believe I can teach my dog Latin, so why wont anyone help me. I give up, abuse everyone else and leave. A month later, someone asks for help to teach their dog Japanese. 
Thats whats happening here, the same idea is popping up again. We dont want to offend you, but we believe from the bottom of our beings that what you are trying to do wont work. Just remember the basic rule, nothing is 100% efficient, so output is always less than input. Where does the extra power go? Heat mostly, lost in mechanical friction or electrical resistance. Some is lost as radiated energy, like radio or magentism. To get power out, you need to put more power in. Our windmills are only about 30% or so efficient, so for every 1000 watts of wind power, we get 300 watts of electricity. Solar cells are less than 20% efficient. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
No White house Here. Just real people with real facts. We are trying to save your money by pointing out, it wont work to the extent you are hoping for. We would be only to happy to help you with a system that will work. To give you an example. I have a 12 volt car alternator coupled to a 1 hp ac motor (750 watts) I get about 20 amp out to a battery (240 watts) In the process i loose 510 watts of energy. For my case i dont care as the only use this gets is to charge a flat battery fast, to start a car should i need to. If you drove the DC motor with wind or hydro than the losses dont matter so much as the input energy source is free to start with. Free energy to power out is always a winner. Dont give up just change tact and move forward. Then we can help you get a positive result. Pete. Sometimes it just works |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
Thanks again for your replies. And no, I am not offended. Surely this is a learning phase and I learn from others as well as by example. While what I am trying to do is just make electricity there are many ways to get there. So say I use a DC PM motor and turn it into a wind generator, hook up a charge controller and some batteries, will this setup blow up my inverter. I have seen some info on using capacitors with pm motors when used as a generator. |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi jazzman, There is some confusion re terminology that comes up from time to time. A DC PM motor is a specific unit. The DC indicates that the power source is DC, and the PM indicates that the motor has permanent magnets for the stationery magnetic field. This unit would have brushes and a commutator on the rotor, with a wound armature. These units produce DC of one polarity when spun one direction and of opposite polarity when spun the other. These units will not benefit from capacitors, as the output is a very stable DC, and should not require much filtering. When used as a generator, a blocking diode will be required. Gordon. become more energy aware |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
The whole function of the charge controller is to keep the generator input voltage down to around 14 volts. With this done it should not blow up your inverter. If the input went to 15 volts or higher than damage to the inverter may result. If your battery was to small than it might not be able to handle all the input current and the voltage would go up. Ups inverters are a poor inverter in my opinion and are not very forgiving to voltage fluctuations. I see little point in caps on the input other than in a voltage doubler configuration, as the battery will do the same as caps on the input. If you have a look at a battery charger they have no caps to filter the charge to the battery, and i know of noone here with caps on their wind generators other than as voltage doublers. Pete. Sometimes it just works |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
Thanks guys, Downwind:I believe you just solved my problem. When I had the UPS inverter installed I was using a small battery and the voltage may have gone up enough to burn up the inverter. Good thing it was only a 300 watter. So would there be a problem in paralleling 5 or 6 PM motor outputs to a charge controller. This is assuming all the motors are at the same voltage level. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Its a hard question to answer without knowing more of what you are thinking. The short answer is yes you can, BUT (there is always a but!) you cant just wire all this together and expect a good result. I would think each generator would need to be isolated from each other via a diode. Then you need some form of voltage controller that can handle your system. You will need a battery capacity suitable. A decent inverter compared to a ups that is very inefficient. Its a matter of looking at the big picture and not what you can string together from the junk pile. Junk is good but must be used in the correct way or failure will result as you have found already. Draw a diagram of what you are thinking of doing. You might not always like the answers given to your ideas but whats the point in given bad information just to see you fail. It helps no one. Pete. Sometimes it just works |
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| cobo351 Newbie Joined: 18/12/2009 Location: United StatesPosts: 34 |
Gizmo touched on over-unity early in the posts. Over-unity is the being able to produce more energy with less. Scientist have been studying ways to do this forever and a way to do so has never been found, that I know of. I’m not saying no one ever will, my dog speaks three languages but I can’t understand any of them…lol. Closest thing I have heard to achieving it was, (I think) a guy who built this thing called a “water hammer” (If I understand it somewhat correctly) it uses minimal amount of an energy source to spin a drum which pushes water through small holes causing the water to get hot enough to produce steam. Theory was the steam could be used to produce more energy then what was being used to turn the contraption. As Red Green says “I'm pulling for ya, and we’re all in this together” Cory |
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| jazzman Newbie Joined: 29/01/2010 Location: Posts: 11 |
Thanks again guys. Downwind, my setup would be no different from one who uses say 2 or more wind generators connected to 1 common system.If I basically have 5 pm motors generating say 12volts Dc each and isolate them from each other. Can I just parallel the positives and negatives to each other and connect them to a charge controller. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I see no reason why you cant connect them like that. Just remember if a wind generator is making power it can not be just disconnected from a load via the charge controller as you would do for solar panels. A windmill needs to be loaded all the time, if not to the batteries than to something else as a dump load. Otherwise it will overspeed and self distruct. I dont know a lot about using the type of motors you have and what you can and can not do with them. What are the motors out of. Pete. Sometimes it just works |
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