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Super 7 Going 3 Phase

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GT39028/11/2011 23:44:17
18 forum posts
4 photos
Hello, I am lucky enough to have "proper" 3 phase power comming into my home worhshop, and am going to convert my super 7, question is, if I wanted to have some kind of electronic speed control, do I still need a VFD drive ?


Regards
 
GT390
John Stevenson28/11/2011 23:54:35
avatar
5068 forum posts
3 photos
Yes but you have a choice in that you can use single phase input and wire the motor in Delta or use a 3 phase input VFD and leave the motor in star.
 
You can usually pick 3 phase 440 volt input VFD's up cheaper than single phase because of the demand.
Steve Talbot 129/11/2011 17:26:30
31 forum posts
Hi,
I'm also in the process of converting my S7 to 3 phase but in my case from single phase using a Newton Tesla VFD CL750 sytem. At least I will when the unit is delivered.
 
One thing that none of the available VFD conversion packages contain is a tachometer/rev counter to show spindle speed. I notice that all the Far Eastern variable speed machine tools do include a spindle read out and these are available as spares at reasonable cost, however I'm not sure if these can be altered to use on a S7 VFD set up.
 
I have traced the company that supplied the read outs fitted to Connoisseur lathes but at a cost of £260 +VAT etc.!!
 
I could use a converted bicycle trip computer however I would like to fit something a little easier to read.
 
Does anyone know the source of a suitable read out, even in kit form, at a reasonable cost?
 
Regards,
Steve T
chris stephens29/11/2011 18:10:26
1049 forum posts
1 photos
Hi Steve ,
As you say the NT conversion has no tacho, but if you had bought the VFD from one of the other sources you could use the freq. display on the front of the box as a guide.
chriStephens
Skarven29/11/2011 18:32:56
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93 forum posts
11 photos
Many inverter systems seems to have a display that can be programmed to show the RPM dependent of pole number and... I can see that the CL750 seems to not have one. Being a Mitsubishi system it might have an analog output that can be programmed to be proportional to the frequency, which, if you know the gearing, will give you the rpm on an analog meter.
I'm an old fashioned electronics engineer/programmer that really like analog readings. They are much easier to read.
 
I already have 3-phase 240V and a transformer for 3-phase 400V, so there are no limits, but I'm also installing a VFD on my lathe and mill, and these VFD's have displays on them, but I think the power in watts is more interesting as this is difficult to have in any other way.
For the the rpm, a cheap bicycle computer is good enough for me. You can have them with quite large displays, and as discussed in another thread, they can give you a quick way to calculate cutting speed.
 
This link has many inverters, and even better, links to the manuals!http://www.inverterdrive.com/
Les Jones 129/11/2011 19:33:11
2292 forum posts
159 photos
Hi Steve,
If you don't mind building at tachometer yourself there is a design on my website that may suit you.
I did submit the design to MEW about two years ago but I have not heard of any plans to publish it.
There is a picture of how Roy Stark mounted a hall sensor on his Myford in "My photos" in the album "misc" (For some reason this photo will not insert into this reply.)
 
Les
 
Gray6229/11/2011 19:39:21
1058 forum posts
16 photos
If you want a proper rpm display, have a look at medw if you have any questions, drop Lester an email, he will be only too happy to help.
This tacho is excellent, I built one from tie original designs produced by Tony Jeffree and have modded it to suit but the one Lester sells is superb.
 
regards
 
Graeme
Michael Gilligan29/11/2011 19:43:41
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23121 forum posts
1360 photos
Les,

That looks a very useful Tacho design.
... Thanks for posting the link to it.

MichaelG.
Les Jones 129/11/2011 19:51:06
2292 forum posts
159 photos
Here is the picture that would not insert into my last post. (After loading into paint shop pro and saving a copy of it.)

Les.
Stub Mandrel29/11/2011 20:13:16
avatar
4318 forum posts
291 photos
1 articles

 
This tachometer uses a single AVR and a few transistors (they aren't needed with the latest AVRs which can sink and source a more current.
 
If there is interest I could provide a modest number of single sided boards and pro-programmed chips as a sort of semi-kit. The sensor is a hall effect switch. Will hanlde a few thousand rpm and down to dead slow:
 
 
 
 
Neil
 
 
Steve Talbot 130/11/2011 18:00:24
31 forum posts
Thanks to all who have provided information, how did we manage before WWW??
 
Neil, how much do you think a kit would cost and would it be possible for someone who is electrically dyslexic to build it?
 
Steve T
Stub Mandrel30/11/2011 18:35:19
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4318 forum posts
291 photos
1 articles
Hi Steve,
 
I'll get back to you on that.
 
Neil

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