Hybrid_From_Hell Posted January 18, 2011 Share Posted January 18, 2011 Hi All, Looking to Upgrade my current lathe (Boxford) which has been and is good, but wnat something bigger Thinking about maybe a Harrision M300, or Colchester Student - prob with both is the same - both are 3 phase. So Question is I THINK the Motors are 2 HP, would an invertor be best or a Conversion to SP Motor. If invertor, what should I be looking for ?, again links, suggestions, are the secondhand invertors OK, or has modern technology moved on and a new one is small better cheaper to run etc ? Help Nige Quote Link to comment Share on other sites More sharing options...
fozsug Posted January 18, 2011 Share Posted January 18, 2011 http://www.motorsanddrives.co.uk/page.html?chapter=0&id=9 http://www.motorsanddrives.co.uk/sk-inverters-sk-inverters-single-phase-c-8_9_16.html http://www.motorsanddrives.co.uk/single-phase-motors-mtc-cap-start-cap-run-motors-c-61_25.html Quote Link to comment Share on other sites More sharing options...
Deej Posted January 18, 2011 Share Posted January 18, 2011 As you can see from fozsug's links, the cost of converting to a single phase motor is comparable to that of buying a 3ph drive, so from that point of view it doesn't make much difference. However, I expect that it would be much easier to wire up a 3ph drive to the lathe than retrofit a single phase motor.<br><br>Also, a 3ph motor will be more power dense than a single phase motor (equivalent single phase machine may not fit) and can provide constant output torque (a single phase machine will have 100Hz torque pulsations). The 3ph drive will also have an adjustable output frequency which will give you infinitely adjustable lathe speed (probably a bit pointless but fun to mess about with <img class="bbc_emoticon" alt="" src="http://forums.lr4x4.com/public/style_emoticons/default/rolleyes.gif">)<br><br>Dave<br> Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted January 18, 2011 Share Posted January 18, 2011 Personally, I would pretty much always go down the 3ph motor + inverter route, but then inverters are part of my day job... I would say the advantages of using an inverter out-weigh the cost, especially if you have a suitable 3ph motor to use. Don't get confused with static converters, rotary converters and inverters, they are all distinctly different devices. It's possible to get full power out of an industrial 3ph motor, on single phase 230v, if the windings on the motors are such that you can re-configure the motor for 230v (quite common to find motors are 230v Delta, 415v Star) You ideally want to size the inverter based on the motor fitted to the lathe. There is a limit to the size of 1ph drives available, but this isn't necessarily a problem if the motor is bigger, if you can accept lower motor performance, and there are other ways around that too. 2HP, or 1.5kW is well within the range of a 1ph inverter, so no problems there. Quote Link to comment Share on other sites More sharing options...
cackshifter Posted January 22, 2011 Share Posted January 22, 2011 I'd agree with preceding recommendations of inverter+3phase over all other solutions. You can use it just to convert, but you can also add variable speed, soft start,reversing, braking etc. The flux vector ones maintain the speed under variable load, which is quite important for some turning. I think 2HP is about the most you could drive via a 13A plug ( I have a small lathe with 1.5HP and a 2nd hand Siemens Micromaster 440 inverter bought for about £75 on ebay - I just use backgear or direct and control the speed and direction via the inverter, and it stops quickly with DC braking, but I'm very much a novice)I think Students used to have 3HP - you might need to get a dedicated (20A/32A?) supply for that. I can't speak for other makes but the Siemens are easy but a bit complicated to program - you can get them working with basic settings very easily then play and detailed settings can be done via a PC if you prefer, after Megasquirt it should be very do-able. One other thing to consider is the coolant pump. You can either change for single phase, or I think they'll run if delta wired and with a beefy capacitor on one of the phases (bit naff) or there were some very small inverters for £25 on ebay at one time, or if you are treating the inverter as just a converter you could probably just add it on to the load. Lights will be single phase, but there may be a 415-230 transformer somewhere that'll need taking out. Nigel Quote Link to comment Share on other sites More sharing options...
mickeyw Posted January 22, 2011 Share Posted January 22, 2011 Nige, My Colchester Student (square head type) has a 3HP motor. I am using a 4HP Transwave RT3 rotary converter with great success. I had to add a 30A socket in the garage for this. Make sure you use a MCB with C curve (rated for motors, I think it tolerates the start up surge better.) My reason for using a Rotary converter rather than an inverter is that you simply plug the lathe into it and it works. You retain full use of the stop start controls and switch gear, coolant pump an' all. An inverter connects directly to the motor, eliminating all the machine's original switch gear. The RT3 is a bluddy heavy unit at 70kg odd, so think about where you would install such a unit. Mine sits under and behind the lathe, the Student has a perfect gap for this. Now I have studied the techy stuff behind phase converters, I am attempting to build another unit from bits 'n' bobs, currently being aquired. Hopefully this will work oput a lot cheaper than buying another RT, and will be used to power my Bridgeport that's going in my Dad's garage Quote Link to comment Share on other sites More sharing options...
Astro_Al Posted January 23, 2011 Share Posted January 23, 2011 For what its worth, I disagree with what has been said. Swapping the motors on these typeof machines couldn't be easier. I have a Colchester triumph, the original 3 phase motor is being kept as a spare and the previous owner stuck a single phase in its place - I just left it as is because it works just fine. Its simply a case of unbolting it, swapping the pulley to the new motor and bolting that in. There is nothing to it. Scanning ebay for a while will get you a cheap 1 phase - even if you have to take it off something else. The gearbox on the lathe is already there to control the speeds, you don't need a separate box of electronics. One thing to note though - the suds pump will probably be 3 ph too, so you need to think about that as well. Cheers, Al. Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 23, 2011 Share Posted January 23, 2011 I'm one for swapping motors, and contactor switch, to single phase but that is mainly because I still have some motors in stock. However, were that not the case I would be considering a good converter on the basis that I could then use it on other 3ph machinery. I am still considering that option anyway as I keep ignoring afordable 3ph machines when shopping. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted January 24, 2011 Share Posted January 24, 2011 I'd vote for an inverter too, variable speed, braking and reverse. you can't always find the gear you want in a box of cogs either. I think inverters can also be used to power more than 1 machine. Quote Link to comment Share on other sites More sharing options...
mickeyw Posted January 24, 2011 Share Posted January 24, 2011 I'd vote for an inverter too, variable speed, braking and reverse. you can't always find the gear you want in a box of cogs either. I think inverters can also be used to power more than 1 machine. NO! Inverters can only run one motor at a time. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted January 24, 2011 Share Posted January 24, 2011 NO! Inverters can only run one motor at a time. Not strictly true...... Also, it's not hard to swap an inverter between machines, if you wish. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted January 24, 2011 Share Posted January 24, 2011 Well I was sort of assuming we were talking about the machines in our shed, in so much as we only use them one at a time. You can get inverters that provide several KVa of 3-phase but as none of us have that kind of budget........ Quote Link to comment Share on other sites More sharing options...
beggers Posted January 29, 2011 Share Posted January 29, 2011 I'm interested i tryin to get a bridgeport & maybe a lathe. Could 1 inverter work for both machines (obviously not at the same time)????? Andy Quote Link to comment Share on other sites More sharing options...
Mr Bean Posted February 6, 2011 Share Posted February 6, 2011 An inverter will be limited by the maximum amount of current it can produce. Regardless if the load is from 1 motor or from 10. Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted February 6, 2011 Share Posted February 6, 2011 Static convertors have a minimum rating and the obvious maximum rating, multiple motors or single motors is irrelevant apart from the starting of the motors. So for example having a 10Hp static to run both the lathe 3hp and mill 3hp together would be fine until the only thing running was the coolant pump on the lathe 1/3rd Hp, this would be below the minimum 1/2Hp rating so that would run hot as it would not get the balanced 3 phases. Rotary convertors have no minimum issues. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted February 6, 2011 Share Posted February 6, 2011 An inverter will be limited by the maximum amount of current it can produce. Regardless if the load is from 1 motor or from 10. And speaking as someone who has a long feed from the Meter / Fuse box to the garage, remember that all the POWER has to come down the single phase link. 2.5 to 3.0 kW, plus conversion losses, can lead to some serious volt drop over 'normal' cable, or buying some very thick and expensive cable to minimise the voltage losses. Really, of course, I'm just jealous that you can contemplate installing such a toy :-) HTH Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted February 6, 2011 Share Posted February 6, 2011 As long as your workshop/garage has a decent supply, 2.5 to 3.0 kW shouldn't be an issue. Certainly beyond what you'd want to run of an extension lead, but well within a proper installation's capacity. Quote Link to comment Share on other sites More sharing options...
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