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+-- Forum: Machinery (http://www.metalworkingfun.com/forum-10.html)
+--- Forum: Lathes (http://www.metalworkingfun.com/forum-11.html)
+--- Thread: Electrical question (/thread-2524.html)
Electrical question - Shawn - 02-16-2015
I have been patiently waiting to buy a RPC to drive a 3 phase 440v lathe. It's a 1986 Smart & Brown 1024 VSL. There are a number of personal issues I have been dealing with for the past coupke of years that has kept me from getting serious about getting this lathe up and running. I won't bore you with all the details but suffice it to say those issues have resolved themselves. It occurred to me that I might be able to rewire the motor to run on 220v 3 phase and then use a VFD instead of the RPC and step up transformer I was planning on. So tonight I took the backplate of the lathe and got a couple photos. The motor was built by Brooks and Compton but of course I can't find any information on the Internet regarding this particular serial number. It's a 3hp motor and from what I can tell from the website Brooks & Compton the motor might be dual voltage rated? I am also of the understanding that I "should" be able to run a 50 hertz motor on 60 hertz with no real issues?
I'm going to contact the manufacturer and see what information I can get but was hoping some of you might give me your thoughts on my plan.
Here are a couple of photos.
![[Image: image.jpg]](http://s24.postimg.org/cpoyb0s79/image.jpg)
![[Image: image.jpg]](http://s24.postimg.org/pft6o405h/image.jpg)
RE: Electrical question - Shawn - 02-16-2015
And just because I like looking at what others have in their shop here's a photo of my lathe the day I picked her up last summer.
![[Image: image.jpg]](http://s3.postimg.org/xyhwvcuer/image.jpg)
RE: Electrical question - Micktoon - 02-17-2015
Hi Shawn, nice lathe you havee there, I know Brook Crompton are good quality motors so worth trying to get it working rather than swapping it. I am no expert but looking at the motor plate it does not look like dual voltage type motor so you might have to dig into the windings to get it to run from an inverter.
I am sure others with more knowledge will comment further, good luck getting it sorted out.
cheers Mick
RE: Electrical question - kingcreaky - 02-17-2015
Im pretty sure; it simply depends on how the motor is wired.... if its STAR it can be ran using an inverter, if its Delta, it cant
I cant see well enough from that photo, but in that junction box can you tell whether 3 of the terminals on one side are bridged?
![[Image: Electric-Motor-Star-and-Delta-wiring-and...06x300.jpg]](http://www.electriciansblog.co.uk/wp-content/uploads/2012/08/Electric-Motor-Star-and-Delta-wiring-and-link-Connections-206x300.jpg)
RE: Electrical question - mfletch - 02-17-2015
It doesn't say its a 220-240v on the plate so you may have to get a 220-240v inverter to 380v three phase
RE: Electrical question - Shawn - 02-17-2015
Thanks for the replies gentlemen. I have sent an email to Brooks & Crompton requesting some additional information. I will check tonight and see if it's bridged or not. I haven't been able to find any documentation that shows a Brooks and Crompton 3 phase motor that isn't dual voltage rated so I'm keeping my fingers crossed.
Shawn
RE: Electrical question - Shawn - 02-18-2015
Im not sure if these photos help but the three wires coming into the motor are each on the same poles as three of the wires coming out of the motor W1 U1 and V1. There are a total of six wires coming out of the motor, the other three are all on a single pole together, those are W2 U2 and V2
![[Image: image.jpg]](http://s9.postimg.org/y7b6xzbhb/image.jpg)
![[Image: image.jpg]](http://s9.postimg.org/sumcjunkv/image.jpg)
RE: Electrical question - Lordedmond - 02-18-2015
its wire as Star or Y in other places
so its connected for the higher voltage on the name plate
but someone has been messing with that block it not wired as it should be
W1 V2
U1 W2
V1 U2
for star you link vertical v2 w2 u2 with the mains on w1 u1 v1
for delta you remove the links and place the ink horizontaly w1 v2 u1 w2 v1 u2 with the main still on w1 u1 and v1
the offset on the numbers allow simple linking because each winding is w1 start and w2 end and so on
that motor will not be able to be wire for 220vac so a VFD is out without transformers
a phase converter with transformer would work
also the age of that motor make running on a VFD dodgy they were not designed for variable frequecy use its down to the insulation and iron to copper ratio
IMHO if you want to go VFD then get a package deal, motor and VFD from the same supplier ( often they will program the unit for you )
Stuart
RE: Electrical question - Shawn - 02-18-2015
Thanks Stuart not what I was hoping for but good to know all the same. I'm not sure I understand how the motor is supposed to be wired though? It was running when I picked it up and I do have a step up teansformer that was used on the lathe to go from 220v 3 phase to 400v 3 phase. Does the transformer care how many phases it's converting? Could I use the same teansformer to step up 220v single phase to 400v single phase and then run the motor with a Vfd set to 50 hertz? The lathe has a built in variable speed capability so I could leave the vfd set to one speed.
Thanks again guys for the help.
RE: Electrical question - Shawn - 02-18-2015
Would it be possible and reasonable to consider getting the motor rewound for 240v 3 ph? Then I could use a Vfd and keep things simple?