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Forum Index : Electronics : Electris motor for output testing of genn
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ozetrade Regular Member  Joined: 15/10/2005 Location: AustraliaPosts: 59 |
I have a really old double ended 240v bench grinder, which I would like to setup to drive Fisher & Paykel gennies for rpm/voltage output testing - it runs @ 1500rpm. Now I know I can use pulleys and/or a gearbox to reduce the rpm of the motor, but I would prefer to be able to vary the speed of the motor via some sort of adjustable switch/dial - say like a light dimmer switch. Is this possible? What can I use? Greg Greg Just North of Brisbane in Redcliffe OZeTrade.net |
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| sangeff Newbie  Joined: 05/11/2005 Location: AustraliaPosts: 29 |
Hello Greg. Its my first time on but I may have an Idea for you. My uncle used to have a speed controll on his bench mounted jigsaw and it was just a light dimmer switch, used to work fine though. |
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
No , you can't vary the speed of an induction /split phase motor-- You have to use an expensive Variable frequency drive (VFD) unit , around 400 bucks ,I'm told. the only type of ac motors you can vary are your "brushed" portable motors-jigsaw;drill;sander;router;angle grinder;Etc. Bye the way you will burn out a bench grinder motor(or it will get very hot). I estimate you will need at least a 2 HP motor (of either sort) ac or dc. The expected o/p of a F&P COULD be 1000watts. So , 750 watts being 1 HP ,you can see you are asking too much of any drive unit below 2HP. I burnt out a 600 watt 1/2 inch bosch drill and a 750 watt petrol pump bowser motor(they are brush type motors ,if you can get your hands on 1 )-- so the next drive motor for me will be 2 HP.
Hope this helps Bruce Bushboy |
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| ozetrade Regular Member Joined: 15/10/2005 Location: AustraliaPosts: 59 |
Thanks Guys, sangeff - you were right...just not the right sort of motor :) Bruce - I have a variable speed 600 watt drill myself. If I made a bracket mount for this and use a say a 3:1 reduction(larger pulley on the F&P), would that help reduce the strain on the drill? I just want to be able to control the rpm of the F&P while I take voltage and amp readings at set rpms. Since I'm building a vawt, I was only going to test up to 4-500rpm in 50rpm increments. I ask the question because $$ aren't readily available to spend on the right stuff at the moment. Greg Greg Just North of Brisbane in Redcliffe OZeTrade.net |
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| sangeff Newbie Joined: 05/11/2005 Location: AustraliaPosts: 29 |
for $50 you can buy a secondhand 3hp brigs&straton engine I bought an almost new 5hp for my cement mixer from a mower shop just north of brisbane for $100. then you get a backup motor as well or you could sell it and get your money back when finnished. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Yes, the petrol driven engines are a good grunty test driver,but bloody noisy,hey ? Your 600 watt drill will work ok ,just make some timber blocks cut out to fit around it (two halves) and secure these to your bench or whatever- you may have to weld up a 1/2' or 3/8' drive shaft with a pulley arrangement on it - Be careful ,and check the heat it will produce , go away and let it cool down --sort of thing. Should be ok for testing -or go to the metal recyclers and see if there is some "largish" motor being tossed in some old machinery equip-chances are the motor will be ok
Bruce Bushboy |
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| MrBungle Newbie Joined: 07/10/2005 Location: AustraliaPosts: 34 |
Strap it to your excersise bike! 
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| sangeff Newbie Joined: 05/11/2005 Location: AustraliaPosts: 29 |
Hey Greg I hava an old petrol pump motor if you want to borrow it the start switch is dodgy (its centrifical) but if you give it a flick jst before you turn it on it goes fine, It has a 2 1/2" pulley on it. Anyway give us a shout if you want to borrow it 0409620975 Geoff Clontarf |
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| ozetrade Regular Member Joined: 15/10/2005 Location: AustraliaPosts: 59 |
I knew I'd seen that username/member before - eBay. Catch up with you soon. Greg Greg Just North of Brisbane in Redcliffe OZeTrade.net |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hey, Geoff and Greg - how about we get together and check out some gear-- I'm inviting you up to Mt.Tamborine if you are interested- about an hour and a bit from your places 07 55453513- and anybody else that lives locally also
Bruce Bushboy |
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| ozetrade Regular Member Joined: 15/10/2005 Location: AustraliaPosts: 59 |
I'm up for that. Greg Just North of Brisbane in Redcliffe OZeTrade.net |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Bruce has the cleanest workskop in the southern hemisphere. True. When you visit Bruce's place make sure you take some wood shavings and metal filings. When he isn't looking spread them around the floor, so it looks like a proper workshop.
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hahaha-- Not that way now ,Glenn, so many 'irons" in the fire at present ,I haven't had time to clean-up. But I will be happy to have any visitors this Sunday. A mighty site Glenn, congrats and thanks from all of us
Bruce Bushboy |
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| ozetrade Regular Member Joined: 15/10/2005 Location: AustraliaPosts: 59 |
....well look at that! Amid all of that electronics equipment = is that a fishing rod I spy sneaking into the top of the picture? Looks kinda new...has it had much use? Greg Just North of Brisbane in Redcliffe OZeTrade.net |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Eh Glenn, Have ya got any pic's of Bruce ? We could morph a photo of Bruce in my workshop but it might hard to find some clear floor space and my shed is only 12x11 metres. Cheers Bryan  |
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whirlybird Newbie Joined: 08/02/2006 Location: Posts: 27 |
Well bruce it seems that your reputation proceedes you. They say that cleanliness is next to godlyness.But I am sure with a little help from some friends I could insert the picture of you that was taken here into Brians workshop so that people will know that you are realy human I am because I am.I am not always right but often I am. |
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mrpackethead Newbie Joined: 11/11/2006 Location: New ZealandPosts: 17 |
So simple and obvious that its not obvious.. How about using another smart drive as a motor to drive another smart drive as a generator.. Whats doubly nice, is that standard smart drive shaft has two sets of splines.. Every thing should be as simple as possible. Not simpler. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Good idea but.... We played around with using the F&P as a motor for a solar car a few years ago. The F&P needs a 3 phase AC supply to run, and this can be achieved with some fancy electronics ( its what the control board in the F&P washing machine does ), and we had a hard time making a reliable controller. About 50 blown mosfets later we gave up on the idea, we could get it to run but not reliably. So it could be done, but the electronics would be a real challenge. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| mrpackethead Newbie Joined: 11/11/2006 Location: New ZealandPosts: 17 |
Hi Gizmo.. What i did'nt say, was that i've got a controller that works very well ( and relaibly ) with teh F&P motors. I used the controller on an evaluation board available from ST. http://www.st.com/stonline/products/literature/ds/11867/stev al-ihm001v1.htm I could'nt find anyone in NZ or Aussie who distributed them, so i bought it from digikey.. Total cost for your first one is about US$150, ( which includes a Indart programmer for the microcontroller ), and then about US$90. If you were building it from strach, theres probalby less than $25 worth of components in it. If i had unlimited time resources i'd probalby design a kitset for people to build, but right now i just could'nt slot it into a busy schedule.. but happy to pass on any hints. The motor actually is a BLDC motor.. ( brushless DC ), not an AC. And to make it run well, you switch it with a trapezial shaped waveform. Without a microcontroller such as the ST7MC which is designed for the task, this woudl be a nightmare to build it with discrete electronics. The kit mentioned above lets you program the motor to do all sorts of trickery. It seems from talking to a few people around that they have all struggled with this problem.. Every thing should be as simple as possible. Not simpler. |
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Seeya next Sunday.
