Thread: Hamatu Lathe on Single Phase

After much procrastination I have finally got my Hamatu HAT 20 lathe running on single phase power. Its a 17 X 57 with a 3.7kw(5hp) motor

Since I already had a suitably rated VSD (7.5kw 3 phase in and out) I elected to leave the motor in the original star configuration and feed the VSD with 480 volts across 2 of the input lines. To step up the 240 volt supply to 480 volt I used some auto-transformers I salvaged from the power supply of an old medical laser unit. This was an American machine adapted for Australia so 3 phase 415 was stepped down to 208V using 3 auto-transformers.
I used 2 of these transformers in series to convert 240 up to 480 v.

The Danfoss VSD I'm using will run ok on single phase input power but must be de-rated. I figured that a 3.7 kw load would be ok on a 7.5 kw drive. I stripped out the original contactors and motor overload. Installed 3 control relays to maintain the original functions of the start and stop buttons, the forward-stop-reverse lever and the foot brake.

So how well does it go? Generally I happy with the conversion but there is an issue running the lathe at the 2 top speeds. At 1000 rpm the drive is sensing the missing phase and giving a warning but at 1500 rpm the drive is pulling the speed down to compensate and I can hear the speed hunting.

Obviously if I want to run these higher speeds some changes are needed.The issue here is the ac to dc conversion within the vsd. The single phase input results in extra ripple in the DC stage of the drive. The solution may be to fit some extra external capacitors but for now I'll just restrict my usage to 1000 rpm or lower.

What surprised me is the motor power required to spin up the lathe without actually cutting metal. At 1000 rpm according to the VSD, the motor is using about 2.5kw. Maybe I need to use some low friction oil in the gearbox.

At 750rpm and below the electrical performance is perfect. However there is some slight knocking from the headstock gearbox in the low 6 speeds so further investigation is needed in this area.

I realise that a machine conversion of this nature isn't suitable for everyone with the extra equipment required to step up the voltage but it may be of interest to some, especially those with 2 speed motors which are not easily changed from star to delta configuration.

So now I'm chasing up some basic tooling and making the chips fly.

John

what model Danfoss?

I used to do put danfoss drive on the end of SWR lines all the time, you just need to change a few parameters.

-Josh

Originally Posted by Brobdingnagian

what model Danfoss?

I used to do put danfoss drive on the end of SWR lines all the time, you just need to change a few parameters.

-Josh

Hi Josh

It's a VLT6008. Not really ideal for a constant torque load like a lathe.

I have set parameter 410 (phase imbalance) to "warning". The other options were "trip" and "warning and de-rate".

If you can suggest some other changes that would be great.

John

I'm not sure if I have the setting for a 6000.

I'll look it up latter today, and let you know.

Originally Posted by Brobdingnagian

I'm not sure if I have the setting for a 6000.

I'll look it up latter today, and let you know.

Thanks Josh.
I've also realized that the 6008 is actually only rated at 5.5 kw. When used on single phase I probably shouldn't expect much more than 3 kw output.

John

Hi John,
Bearing in mind I think you have more idea about these things than I do, just one of my "ideas".

Could you supply the VSD with DC? sure it would mean you were only using two diodes* but wouldn't 680VDC through two diodes be better than 480VAC through four? Its amps you are worried about with a diode isnt it?

Stuart

*would bypassing the diodes be a problem? hmmm what would the caps think about that???

Originally Posted by Stustoys

Hi John,
Bearing in mind I think you have more idea about these things than I do, just one of my "ideas".

Could you supply the VSD with DC? sure it would mean you were only using two diodes* but wouldn't 680VDC through two diodes be better than 480VAC through four? Its amps you are worried about with a diode isnt it?

Stuart

*would bypassing the diodes be a problem? hmmm what would the caps think about that???

Hi Stuart

You can feed DC directly to the drive. In fact there are 2 terminals provided to allow direct access to the DC bus.

The problem I have is the level of ripple current experienced by the internal capacitors. This is due to only supplying 1 phase instead of 3. Most manufacturers de-rate by 50% in this situation to limit capacitor heating.

However you suggestion to supply DC is correct so long as I install some additional capacitors in the external DC power supply.

The other alternative is to source another larger VSD.

John

Sorry John, I can't seem to find my configuration for the 6000.

But there are a number of things other than the 410 Parm you can try. I would just set as warning. but then again the the DC ripple on the 5.5kW drive might be too much at full load.

One is to have a play with the switching frequency Parm 407, I think the default is 8kHz, you may like to drop it down to 4kHz if you can stand the hum.

-Josh

Originally Posted by Brobdingnagian

One is to have a play with the switching frequency Parm 407, I think the default is 8kHz, you may like to drop it down to 4kHz if you can stand the hum.

-Josh

Thanks Josh. I'll give it a go

John

I am about to try the same caper using transformers from a tradesman welder. And a Danfoss VLT. Luckily my application is only a 1 hp drill press. I currently have three phase, but expect to be moving soon to lesser shop (house)

Greg

Originally Posted by Greg Q

I am about to try the same caper using transformers from a tradesman welder. And a Danfoss VLT. Luckily my application is only a 1 hp drill press. I currently have three phase, but expect to be moving soon to lesser shop (house)

Greg

I would think that as long as the drive is close to 2 hp rating you should have no problems.

Are you using the multi tap primary winding as the step up autotransformer. Sounds like a good idea.

I couldn't believe the inefficiency of the ophthalmic laser my transformers came from. 3 phase 415v @ 25 A input for about 5w of light output. Almost all the input power ending up as waste heat.

John

Yeah, the drives that I have are all 2 or 3 h.p. i collect the welder tomorrow, so I will have a better idea of how to proceed soon.

I am cranky as hell because I was going to install a new SEW Movitrac on my Deckel...it has an external braking resistor and everything. Now I guess I will convert the Deckel to 240v three phase as I have a suitable single phase input DanfossVLT for that.

I am puzzled by all of these new-in-box Danfoss drives that I have found on ebay US and Gray's here for under $150.00. What don't I know that everyone else seems to?

Originally Posted by Greg Q

Yeah, the drives that I have are all 2 or 3 h.p. i collect the welder tomorrow, so I will have a better idea of how to proceed soon.

I am cranky as hell because I was going to install a new SEW Movitrac on my Deckel...it has an external braking resistor and everything. Now I guess I will convert the Deckel to 240v three phase as I have a suitable single phase input DanfossVLT for that.

I am puzzled by all of these new-in-box Danfoss drives that I have found on ebay US and Gray's here for under $150.00. What don't I know that everyone else seems to?

What model are the? FC51's perhaps?

Danfoss have a range of drives that they only bring into the country for specific customers. These tend to be the cheaper (relatively dumb drives designed for external controllers) unlike there more comprehensive FC102/202 general purpose series.

One thing I can say about Danfoss VFD's is that they are of a good quality across the board, even their cheap ones are reliable. A place I used to work at would used range of drives in their product over many years, and have settled on Danfoss for the last 5 or so years because of their reliability. We would have shipped at least 50-60 drives a month when I was working there, and very few have problems, and that did have problems where mostly due to power supply problems such as brown outs and lighting strikes.

-Josh

[QUOTE=Brobdingnagian;1636779


One thing I can say about Danfoss VFD's is that they are of a good quality across the board, even their cheap ones are reliable. A place I used to work at would used range of drives in their product over many years, and have settled on Danfoss for the last 5 or so years because of their reliability.

-Josh[/QUOTE]

We have used Danfoss drives at work for many years and have been very happy with their quality.
Naturally they are going to cost more than a similarly sized Huanyang drive and that's probably hard to justify in a home workshop environment.
I was recently lucky to score a near new FC302 3.3kw drive on ebay for just over $100 inc freight so that will come in handy for a future project.

John