Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Katoh on June 15, 2011, 10:42:22 AM
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Colleges
Just getting parts together to do a conversion on a lathe.
Looking at a VFD at present with a 2hp capability should work really well on a 1hp motor. Now I'm getting a bit confused on the subject of voltages and outputs , and the manufactures have got back to me saying I'm right but there talking about things that dont even apply to the motor ratings I'm looking at.
Question.
If your supply to the VFD is Single phase 240v input, the output will be 240v 3phase. So do we look for a 3 phase 240v US style motor or a 415v 3Phase Aus/UK motor? Remember this is just VFD not a step up or down transformer.
Delta to star connections and starters really should have nothing to do with this, they dont come into play till we look at 10kw plus motors, starting under load.
Thanks
Katoh
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The motor HAS to match the supplied voltage (;-)
Just a thought (;-) TP
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The motor HAS to match the supplied voltage (;-) +/- 5%
Just a thought (;-) TP
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Ok thats true, but are we looking at the output as 240v a phase or combined, this is were I am getting lost.
If its per phase than 415? or 240v input = 240v motor?
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Often 415 motors can be connected Delta and that will make it 240v
Hood
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Hood
Yes delta and star connections change things around, 240 to 415, I dont know if one looses rpm while the the other looses torque?
If we get out of the VFD 240v /phase isn't that the same then as mains 3 phase?
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Katoh,
Mains 3 phase is 415v between each phase wire. (In turn each phase wire is 240v to Neutral).
Tweakie.
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So if single 240v input into the VFD and we have 240 per phase output, we effectively have a 415 supply?
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A VFD which can be connected 240v single phase on the input will be 240v 3 phase output I think.
Hood
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If what your saying is correct then each phase outputting the VFD will be 110v to make a 240v 3Phase supply.
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I agree with Hood 240V ;)
Tweakie.
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Where do you get 110v from ?
There are only 3 outputs and it is 240v between each output making the output 240v, 3 phase.
Tweakie.
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The output will be 240v 3 phase delta. With 240V between any two legs. It can't be Y because there is NO neutral.
(;-) TP
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If on the mains you meter from active to neutral you should have 240v/ phase. If you have a 3phase 240v US style power and you meter between an active and neutral you should have 110v. Theres may reasoning.
I'm looking at this from the motors side. with a 3phase motor (415v) each phase entering the motor is carrying 240v, and that's what should be coming out of the vfd on each phase.
I think.
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US power 3 phase Y, phase to Ground 120v Phase to phase 208v , 3 TX bank
240v 3 phase delta with high leg. A to N 120v B to N 120v C to N 240v 240v phase to phase , 2 TX bank
240v open delta 240v phase to phase no neutral , 3 TX bank
BUT all that is irrelevant as you have 240v 3ohase output and NEED a 240v 3p motor (;-)
(;-) TP
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Best you read your VFD manual and "How to connect a motor" - if you experiment, as you suggest, you could loose both your motor and your VFD.
Henk explains dual voltage motors here http://www.scribd.com/doc/22398221/Star-Delta-Starting-and-Dual-Voltage-Motors-Explained
Tweakie.
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It sounds like so far this assumes that the 3 phase has the same characteristics as mains provided 3 phase.
A VFD has to control frequency and MEAN voltage and current and usually does this through PWM signal that is sine wave in shape, if it did not, the 3 phase rectifier and capacitor bank on the input of a 220v VFD would provide constant sine wave of >300v amplitude due to the level of the DC.
In any case, all the VFD's I have used have a parameter setting for motor voltage, within the VFD range that is.
Also because it is electronically produced, there is no Star or Delta, just three phases spaced 120deg apart with ~220v between phases.
N.
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I dont have a lot of experience with VFDs and even less with single phase input ones. Having said that I have never seen a VFD that outputs a higher voltage than the input voltage and for the single phase 240v input ones I have never seen one capable of outputting more than 240v three phase. As said my experience with VFDs is limited so take of it what you will.
Hood
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Having said that I have never seen a VFD that outputs a higher voltage than the input voltage and for the single phase 240v input ones I have never seen one capable of outputting more than 240v three phase.
What of the 120v 1 ph input models that run a 240v 3ph motor?
http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_%28120_-z-_230_VAC_V-z-Hz_Control%29
Agreed they are in the lower HP range.
You may not run across them in the UK due to no 120vac generally.
N.
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Nope never seen them here, only 110v we normally have here is on sites for power tools.
So are there 240V single phase input VFDs that will output 415V three phase? I have never seen one but again my experience with VFDs is limited.
Hood
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So are there 240V single phase input VFDs that will output 415V three phase? I have never seen one but again my experience with VFDs is limited.
Hood
Never ever seen those listed, only the 120v input.
N.
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Ok so safe to say that for Katoh he will have to get a motor that can take 240v, whether thats one thats only 240v or a dual volt motor.
Hood
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Having said that I have never seen a VFD that outputs a higher voltage than the input voltage and for the single phase 240v input ones I have never seen one capable of outputting more than 240v three phase.
What of the 120v 1 ph input models that run a 240v 3ph motor?
http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS1_%28120_-z-_230_VAC_V-z-Hz_Control%29
Agreed they are in the lower HP range.
You may not run across them in the UK due to no 120vac generally.
N.
Exactly to my point Nosmoking, If in the states you have VFD with 110v input to drive a 220v 3ph motor then it only make sense that a 240v input should drive a 415v motor.
I'm going to work now, so I am going to hassle the electrician again that works there.
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Exactly to my point Nosmoking, If in the states you have VFD with 110v input to drive a 220v 3ph motor then it only make sense that a 240v input should drive a 415v motor.
The 120v in 240v out are specifically designed that way, you may be out of luck finding a 240 in 415v out, unless designed that way.
I have never ran across one.
N.
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Gentlemen
After a full on day of conversing with our local sparky, we both ended up totally confused on the issue at hand. After now another 3 hours wasted on google and numerous phone calls around the country, we may have a little light at the end of this subject. From what I have been able to understand from what I have read, the following happens.
Input into the VFD = 240v single phase
output is 240v 3 phase (240v per phase if taken to earth or back to neutral) but still only 240v across phases.
A 415v 3phase motor if the wirings are in star or wye configuration will work fine if wired to delta on the inputs.
Motors that are internally wired delta will need a 415v input across actives or can be run with a Wye - delta starter, these are more likely in very large motors.
I would love for someone to confirm my findings!
Cheers Katoh
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Gentlemen
Just to add to my last post if there is anyone else needing the same information, a little more reading and some more information.
To carry on from before, if your motor has 6 terminals were you connect your wires too the motor your job is easy, and your motor will run happily with the vfd. Refer http://www.backsaw.net/pics/MotorWiring.jpg for wiring diagram.
If you only have 3 terminals you may then have to do some internal works to the motor. Again this is only for motors that are wound in wye or star configuration and yes they are 415v 3 phase motors.
99% of motors under 5kw will be wye or star not delta wound.
For the adventuress here is a link to another forum were it is described how to rewire it yourself.
http://www.woodworkforums.com/f189/finally-finished-my-260-a-116004/
For the less I'm sure it would be a cheap exercise to have it done. I will find out soon.
Cheers
Katoh
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I think you have seriously over complicated the process(;-) 3p motors have 3 phase wires to hook to. abc sets the phase rotation or the direction the motor will run. Dual voltage motors HAVE a set of extra leads as well that allow you to put the windings in series or parrallel. high voltage or low voltage.
Match the VFD output rated voltage to the motor rated voltage and you are good to go. That is all there is to it. If your base rotation is backwards then swap any to input leads to the motor.
(;-) TP
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TP
I realise that I may have made things more complex, and yes you can get motors that have both 240/415 or basically duel voltage input.
At least now we have basically clarified that from a VFD input of 240v single phase then you have to wire it to the 240v input or delta winding on the motor. Not to confuse things further I did find tonight a VFD 240v input single phase to 415v 3 phase output. But for 400 pounds they can keep it.
I am looking into using a motor which is not duel voltage is just simply 415v 3phase star or wye connected in the windings for the lathe. I would just like to say that this motor can be used with the 240VFD output, it just needs a bit of re-wiring as stated earlier.
This has been a real learning curve for me and now I know basically what will and wont work.
Katoh
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One Other question on the same subject. With a single phase input into the vfd do you need to install a line reactor and EMI filter and how to you wire a single phase into a 3 phase line reactor?
Thanks
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YOu really need to get the Y or delta out of the thought process. You have 3 leads abc you do not have a neutral in most cases(never seen one here). HOW the motor was WOUND is irrelevant to your process.
The hook up is abc voltage is measured phase to phase. A voltage check phase to GRND is useless info in the case of the motor performance. You have to match the VFD output to the motor input requirement.
Keep it in that thought process and you are good to go.
Just a thought(;-)TP
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LOOK at the suggested MANF hookup they will SHOW the recommended placement of recommended components. Normally you only hook up single phase to single phase supplies(;-) IF you hook single phase to a 3 phase source you best know what you are working with. there are MANY variables to content with. SOme can kill you when you are not looking. SOme will just let the magic SMOKE out of your controls.
Be safe, IF you do not know it for a FACT consult a trained and qualified electrician. (;-) TP
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One Other question on the same subject. With a single phase input into the vfd do you need to install a line reactor and EMI filter and how to you wire a single phase into a 3 phase line reactor?
Thanks
Most modern VFD's have harmonic distortion suppression now on the input, if fitting one at all I would be inclined to put a 3 phase reactor on the motor side, it is easier on both motor and drive, especially if using a non-vector rated motor.
Vector rated motors are designed with VFD use in mind.
N.
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Gentlemen many thanks for the comments once again. Another long night with lots of reading, I found the instructions to line reactor I used on my router, and that had a part in there regarding using single phase input. According to the manual there are three inputs ABC you put your active through A and neutral through C and leave B blank. then input into the VFD. They also recommend to use a line reactor before any VFD.
Still debating on the using an EMI/RFI filter, I have one on the router but I also used shielded 3 phase cable, maybe just the Shielded cable will be enough?
Cheers
Katoh
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Theo
I just got a motor from Royce Cross in SA that will run from a VFD as per all the discussion here, just go to their site and look at the specifications for the motors, or ring them they are very helpful. Freight to my place was around 27.00 and it arrived in three days.
Will
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Hi Will
I spoke to them through the week, and they are very good. I ended up buying a motor off Ebay (very Cheap) but the bloke could not tell me how many terminals it had coming out of the motor, I dont think he understood what I was asking. If its just got the three terminals up top it will be permanently wire in star or wye. I will have a go myself to convert to delta for 240v, if I stuff it, no real money lost just experience gained.
After talking to Hood I have got my eyes open for a large AC servo for the right price, until then either the motor I bought or I buy a new one from Royce Cross will have to do.
Hows your build going?
I've got all sorts of things coming for mine, ball screws, motors, inverters, opto's ect ect. should get here in one big lot and then the fun starts. The only thing I haven't organised yet is the power supply, the fella I bought my last ones from is no longer trading and I cant find anyone whos got the same sort. I am tossing up to wait a little longer for Peter Homman to get new stock in as he has one smaller then my previous ones but sufficient for the lathe or just to build one, The money comes to nearly the same.
Cheers
Theo
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Theo
The lathe is in the works at the moment, I have the VFD and motor and am still researching the other bits and pieces, at the same time I am converting a Chinese quick CNC router to Mach 3, just about ready to get into it, I have all the bits and pieces here, I am just a bit unsure how to wire some of it up. The original setup used 24 volts for the limits and controls and I have an Opto 22 board and modules to put in so I can still use the 24 volt side of the system, just trying to work out how that fits into the system.
Will
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Good luck with that Will, if you get stuck Ill try my best to help, You could also put in a post here there's some clue'y people on this site.
You can run the original 24 volts for your limits, just put it through a relay and then use your whatever your voltage is for your board, that's how mine works. I hope that doesn't sound too confusing.
Theo