3 phase motor advice please

I have a Denford Viceroy lathe with a 3/4 HP 3 phase motor. I also have an Altivar inverter with which I run another identical machine
successfully.
The problem motor (dated about 1965) runs smoothly but at very low power, it will only start the lathe in lowest direct gear and you can stall it with a hand on the chuck. The three input wires connect to three wires inside the motor, no other wires/connectors visible. Am I right in thinking that the motor is wired in star configuration and is expecting 440V? Also, since no other connections visible, I'd need to dismantle the motor to find the star point, then re-wire?
I've trawled the archive on Google but I'm not sure I understand everything I've found.
Thanks for any advice. Richard
--
Richard Evans

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

'Fraid so on both counts. You have two, nay three alternatives. [1] Find the star point and bring 3 wires out and wire then so the end of one joins the end of another to make a triangle up then apply voltage to these three points [2] Find a star/delta 6 wire motor. [3] lastly it's bodge but it will get you running is to re program the invertor for a base voltage of 28 Hz not 50 Hz. this will give you full power up to 28 Hz but it will drop off after this point. Sometimes this is enough as higher speeds usually don't need as much power.
In view of the current posts about spelling and Grandma, sod it this is advise not a bloody thesis -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 19 Nov 2005 13:49:58 GMT, John Stevenson

Where are you? I'm pretty sure I've still got a dual voltage motor off a Boxford, same sort of size.
Cheers Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 19 Nov 2005 15:04:59 +0000, Tim Leech

Just checked, it's a Crompton 3/4hp 1425 rpm 3-phase dual voltage, foot mounted, not totally enclosed. Let me know if that would help.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Many thanks, and thanks to John as well for confirming my suspicions. I'm not sure yet but Tim's motor might well be very useful indeed. It's a complex situation (aren't they all?)
I have the two lathes and a polisher all with the same pattern of motor. One lathe and the polisher work fine. I've never used the second lathe except for horizontal slotting using a router, so I was surprised to discover the problem. Sod's Law, the lathe which works OK is fairly clapped out and the one with the problem is a fairly unworn machine.
I make a living by using the lathe several hours daily (bagpipe making- see the website if interested), so it's all pretty important.
I've got a Boxford BUD arriving next week to replace one or both Denfords, that's 3-phase too (which I much prefer), but more recent, about 1980, so I hope it will be easy to modify the motor.
I'm going to look inside the motor in the polisher tomorrow (oh joy, sore knees and scraped knuckles- motor in a small space at ground level! ), try to see what's going on.
Thanks again Richard
--
Richard Evans
Northumbrian and other bagpipes
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I took the easy option and just swapped the motor from the surplus lathe to the one I want to use- didn't fancy messing about looking for wires inside. The swapping reminded me of working on my old Land Rover- difficult to access nuts and bolts, obscure bolt head sizes, nuts hard up against casting webs, etc.. An interesting design feature, also reminiscent of Landrover, was the discovery that the motor had tiny oil cups on the bearings, totally invisible without removing the motor and unused ( I think) since the thing was assembled in 1965. Cheers Richard
--
Richard Evans

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hi Richard.
Two of my colleague do woodturning and fitted some sort of convertor to their motors to wourk on single phase. It apparently allows them to regulate the speed by turning a dial that increases/decreases the frequency. Apparently it works great.
I'll find out more tomorrow for you if that helps.
Declan
wrote:

Regards
Declan Barry
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi, Thanks for the offer, I already have a gadget that does exactly that. It was the wiring of this particular motor the was the issue.
My wife and I managed to get the old Viceroy lathe out of the workshop without damaging ourselves (or the lathe). It's amazing what you can do with a few offcuts of steel tube for rollers- even got it over the doorstep without fatalities.
There's now a gap waiting for the Boxford replacement, which I hope will arrive before the snow! Cheers Richard
--
Richard Evans

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.