240v single phase to 415v 3 phase conversion

[malb]

can you put a stop/forward/reverse switch between a VSD and the motor, say like a drill press so you can tap with it?


Thanks
Jake.

No, the VFD must connect to the motor directly. Any attempt to break the current flow while the motor is spinning will destroy the output devices in the drive.

You can fit a forward stop reverse switch to the low voltage control inputs of the drive unit, but you won't get instantaneous response because the VFD ramps the variations moderately slowly and the motor/mechanical drive will have inertia to overcome.

[Oldneweng]

Phase converters do not change the voltage... the 240V in units output 240V as well, not 415V...

Some motors are easily converted to run on 240V three phase... Others are not....

I have found that out in my reading but all the discussion seems to be about running 3 phase when that supply is not available. That is what I am looking into. I will have to check the plate on the motor if I find one available to see if a phase converter is suitable.

Big Shed. As above.

Stuart. My lathe finds it a bit of a struggle to acheive full speed in top 2 gears. I have to slip the clutch. This is with a drop from 3hp 3 phase to 2hp single phase. Given the reduction in efficiency in single phase motors this may be in the same range as you mention.

Most of my info came from Drives Direct - Digital Phase Converters - How To Choose.

So after all the posts I have read about using a VFD / VSD etc to use 3 phase when only single phase is available, this method is very expensive and only a second last choice?

What is the difference between VFD and VSD then?

My best bet then is to see if the motor can be wired in a delta config and then run with a VSD with 240v output or buy a 3hp single phase motor. If buying a single phase motor I may also have to buy another switch which cost $200 for my lathe. Single phase switches tend to be of smaller capacity due to the higher voltage and 3 phases. This is one possible advantage of using a VSD. It seems the current price is about $145 for a 2.2kw unit. It also seems that this is suitable for a 2.2kw motor as one of the units I looked at had both a 2.2kw rating and was classed as suitable for a 2.2kw motor. This is one thing that concerned me with induction motors.

I have the possibility of another lathe lined up. Much better than mine. I am waiting on a decision. Two other people have expressed interest but have done nothing. It is about the same size but longer between centres. About 1000mm from end of tailstock tube to chuck jaws. I have seen a picture of one the same (except this one also had a DRO) and is listed as 1000mm centres. I believe that it is far far more accurate due to wear.

Of course I could always use the motor and switch from my lathe. Depends on a number of things.

Dean

[Acco]

Sounds like you guys could answer a question for me as well.

I bought this 3-phase-240v-415-0.75kw-motor with the intention of mounting it on my mini woodlathe and will need to acquire an inverter for it and from looking at all the links you guys have posted and more searching on eBay, this raises my question.

Plenty of 1.5 and 2.2Kw inverters out there to buy but it seems 0.75kw are rare, so the question is, will a 1.5kw inverter run a 0.75kw motor without any problems?

[Oldneweng]

Hi Jake,
No
But you could do the forward/stop/reverse with the VSD.

Hi Big Shed,
Thanks. I remembered the post but didnt think I had a chance of finding it(tI thought it was in another thread, not that we do that sort of thing around here ). It confirms(I'm pretty sure) that I've picked the correct ones, I need something to pad the order up to $20 altronics min)

Stuart

You could double it up and send a set to me just in case.

Dean

[Stustoys]

Hi Dean,

Stuart. My lathe finds it a bit of a struggle to acheive full speed in top 2 gears. I have to slip the clutch. This is with a drop from 3hp 3 phase to 2hp single phase. Given the reduction in efficiency in single phase motors this may be in the same range as you mention.

You mean getting up to speed? Shouldnt be a problem for a VSD.

Most of my info came from Drives Direct - Digital Phase Converters - How To Choose.

So after all the posts I have read about using a VFD / VSD etc to use 3 phase when only single phase is available, this method is very expensive and only a second last choice?

No No, 240V input- 240V output VSD/VFD is fine. Its the 240V input-415V output that is the " very expensive and only a second last choice"

What is the difference between VFD and VSD then?

Same thing, different name

My best bet then is to see if the motor can be wired in a delta config and then run with a VSD with 240v output or buy a 3hp single phase motor. If buying a single phase motor I may also have to buy another switch which cost $200 for my lathe. Single phase switches tend to be of smaller capacity due to the higher voltage and 3 phases. This is one possible advantage of using a VSD. It seems the current price is about $145 for a 2.2kw unit. It also seems that this is suitable for a 2.2kw motor as one of the units I looked at had both a 2.2kw rating and was classed as suitable for a 2.2kw motor. This is one thing that concerned me with induction motors.

It needs to be a dual voltage motor(which it most likely will be), but you have to have a look at the plate.
I would stay away from the 3hp single phase motor, the start up current may give you problems?? It would likely cost more and you dont get all the pluses of having VSD.

Stuart

[jackaroo]

Hi Jake,
No
But you could do the forward/stop/reverse with the VSD.

Hi Big Shed,
Thanks. I remembered the post but didnt think I had a chance of finding it(tI thought it was in another thread, not that we do that sort of thing around here ). It confirms(I'm pretty sure) that I've picked the correct ones, I need something to pad the order up to $20 altronics min)

Stuart

Hi Stuart, where about are you in Melb? I probably can pick up for you if you order under $20, I might go there again tomorrow again.

[Stustoys]

Plenty of 1.5 and 2.2Kw inverters out there to buy but it seems 0.75kw are rare, so the question is, will a 1.5kw inverter run a 0.75kw motor without any problems?

Other than possibly costing slightly more money, no problems. All my drives are 2.2kW.(you should of course set the parameters to suit the motor you are running though). I figured the money I would save by having some 2.2kw, some 1.5kW etc wouldnt be worth it as you can bet the day I need the big VSD is the day it blows up and I'd only have the small one.

Stuart

[Acco]

Cool, so bigger kw inverter is ok but I would imagine not vice versa, such as 2.2kw motor coupled to a 1.5kw inverter?

[Stustoys]

Hi Stuart, where about are you in Melb? I probably can pick up for you if you order under $20, I might go there again tomorrow again.

Hi Trong ,
Thanks for the offer, but for some reason I thought they were only in Perth, I can duck down there myself.

Cool, so bigger kw inverter is ok but I would imagine not vice versa, such as 2.2kw motor coupled to a 1.5kw inverter?

I might get stoned for this but. No thats fine also, the VSD should be able to look after itself, of course you'll only get 1.5kW from your 2.2kW motor.(long term, they will allow *I think* 150% output for about a minute??)

Stuart

[Oldneweng]

When I say

I believe that it is far far more accurate due to wear.

I mean it has less wear. Just thought I would clarify that.

I am almost looking forward to having a VSD to play with seeing all the options I could have. I say almost as we have lots and lots of VSD's at work and they are great when they work but are a real PITA when they don't.

Issues with them. I have set up a big job and are just about to start when some twit tastes off another job with water straight into the front of the VSD at high volumn. They dont like swimming.

When they first started using them they had older style RCD switches installed which were not very compatable with VSD's. They tended to trip as soon as power was switched on. Had to call up the sparky and wait. Probably 3 other pumps also connected to the same circuit.

They have advantages. Wine hammer is closely related to water hammer and just as loud. Thru 3inch stainless lines it can be very loud. Slow ramp up by using VSD's has made this a thing of the past for the many presses which were the worst culprits. Also saves wear and tear on piping. Some pumps can run at up to 75hz. I did not know that this was just a setting until a repair to our centrifuge pump caused the pump to only do 50 hz. Called the sparky and he pushed a couple of buttons and back to 75hz.

Dean

[Acco]

Thanks Stu, you've been a big help

Will place an order for a 1.5kw inverter soon

[Oldneweng]

You mean getting up to speed? Shouldnt be a problem for a VSD.

One of the benefits.

No No, 240V input- 240V output VSD/VFD is fine. Its the 240V input-415V output that is the " very expensive and only a second last choice"

That is what is meant.

Same thing, different name

Was wondering.

It needs to be a dual voltage motor(which it most likely will be), but you have to have a look at the plate.
I would stay away from the 3hp single phase motor, the start up current may give you problems?? It would likely cost more and you dont get all the pluses of having VSD.

Yes, the plate. Not always easy. Will try but have no idea at this stage what it is like to get at etc. If I get it will be no problem.

I don't think it is likely to cost more! I know it will cost more! All those plusses are looking better all the time.

Dean

[Ueee]

It needs to be a dual voltage motor(which it most likely will be), but you have to have a look at the plate.
I would stay away from the 3hp single phase motor, the start up current may give you problems?? It would likely cost more and you dont get all the pluses of having VSD.

Stuart

Hi,
I have a 3hp 2880rpm single phase motor on my dust extractor. even though our house has a 60amp 3 phase feed it makes all the lights dim on startup......The 5hp shaper motor and 4hp table saw/spindle moulder 3 phase motors don't dim a thing.

[BobL]

Hi,
I have a 3hp 2880rpm single phase motor on my dust extractor. even though our house has a 60amp 3 phase feed it makes all the lights dim on startup......The 5hp shaper motor and 4hp table saw/spindle moulder 3 phase motors don't dim a thing.

My Shed has two power feeds (and two dist boards) - a 20A single phase and a 45A 3 phase. On startup the 3HP single phase DC will trip the 20A single phase breaker but it won't trip the 20A breaker on one of the Phases from the 3 Phase?

[Oldneweng]

Ok. Now I have a bit more info but I still have not received or gone looking for an answer to whether it is mine or not.

I maybe know why the lathe has not been snapped up already. I don't know how long it has been sitting where it is waiting for a buyer but it has started to go rusty on the bed and ther places so If I get it I want it to be soon. It is under cover but exposed to the north side so condensation is getting to it.

A plate on the rear of the lathe says the drive motor should be 7.5hp 3 phase. I don't know if the motor is original or not and I cannot see the motor plate enough to read it. I would have to move the lathe and remove a cover (4 screws) to clean the plate up to read it. I would suggest that nobody is willing to take on a lathe that big without 3 phase power until I came along.

It is a bit bigger than mine in swing over bed (220mm) and in gap (about 300). It has about 52mm spindle hole. Face plate is 400mm while mine is 340mm. Other than that the chucks are the same size. My lathe has 750rpm max, this one 2000rpm. I am guessing that is the main reason for the extra power.

I still think it is possible to run it off a VSD based on what I have read here recently provided I don't expect to use it to its full capacity and I set the max current on the VSD. I think it would do at least as much as my current lathe.

This lathe has a taper attachment on it with micrometer adjustment.

Suggestions please as I want to ask about it tommorrow. SWMBO has said just get it and we will sort the power out afterwards. As we are on a SWER system the only other options are moving or a generator.

Dean