Electrical question - Printable Version

Electrical question - Printable Version

+- MetalworkingFun Forum (http://www.metalworkingfun.com)
+-- Forum: Machinery (http://www.metalworkingfun.com/forum-10.html)
+--- Forum: Lathes (http://www.metalworkingfun.com/forum-11.html)
+--- Thread: Electrical question (/thread-2524.html)

Pages: 1 2 3 4

RE: Electrical question - Hopefuldave - 02-18-2015

Hang on a minute...

If one end of each U V and W are tied together, it IS star wound, which is for the higher voltage!

connect U2 to V1, V2 to W1 and W2 to U1, 240V 3-phase to each join, it should run on 220V in delta.

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CEwQFjAH&url=http%3A%2F%2Fwww.mandc.co.za%2Fpdfs%2FStar_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf&ei=Rd_kVLyhLJfhauP_gYAP&usg=AFQjCNEOHRbe7dfr8gLj31yPccLtYiWH5g&sig2=rIE1CEtwVLV07fpuUmL34w&bvm=bv.85970519,d.d2s

(sorry about the long link, I won't use shorteners as it's impossile to see where they're taking you, and to what) has a good explanation, inclusing what goes wrong if incorrectly connected - page 14 has a nice table showing a delta-connected motor's starting current on 380v (4440 Amps!) and a star-connected motor's full-load output on 240V (down from 185KW to 33KW) - these are in the context of star-delta starting, but apply just as well to dual-voltage motors like the Brook-Crompton, which is a British-made motor originally designed for duall voltage use.

British / European motors are NOT american motors, which all seem to be 9-wire for dual voltage, I've no idea why...

Except my lathe's motor, of course, which IS 9-wire, but for three different speeds 17428

Hope that helps.

RE: Electrical question - f350ca - 02-18-2015

If you have the setup transformer can you not feed the vfd into that.

RE: Electrical question - stevec - 02-18-2015

(02-18-2015, 08:44 PM)f350ca Wrote: If you have the setup transformer can you not feed the vfd into that.

Greg, do you mean STEP UP transformer? Tsk, tsk, watch the spelling lad. LOL

Steve

RE: Electrical question - Shawn - 02-18-2015

Being an electrical noob of the highest order I was hoping to simplify the setup as much as possible, hence the hope to bypass the need for a transformer. The transformer I got with the lathe looks like something you would see in an old Mad Max movie, I don't have a great deal of faith in it. That's based on nothing more than first impressions though. I have also heard that transformers and VFDs don't necessarily play well together.

I'm pleased to hear I can make a few simple wire reconnects and run the lathe on 240v, that will keep things simpler and cheaper as there seems to be a lot more VFDs available in the 240v range.

Here's another question that I probably should have asked or mentioned at the start. The lathe has an oil pump but that is run from a belt drive so no issues there. The work light and coolant pump are run the same electrical system as the lathe motor. Will these work with the motor running on 240v 3ph? If not I think it might be easier to rewire those with their own separate 110v systems?

@Dave, the link didn't work for me but I think I can find it via a Google search based on the name in the address.

I appreciate all the advice and suggestions.

Cheers
Shawn

Edit: is this the page you were talking about Dave?
http://www.mandc.co.za/pdfs/Star_Delta_Starting_and_Dual_Voltage_Motors_Explained.pdf

RE: Electrical question - Hawkeye - 02-19-2015

There are at least a couple of motor rewind businesses in the 'Loops. Google "Kamloops motor rewind" and ask them about rewinding to a specific voltage.

RE: Electrical question - Shawn - 02-19-2015

Thanks Mike, I was going to call a few places tomorrow and see what it will cost. I'm hoping that a simple reconfiguration of the wiring will allow the motor to run on 220v but I seem to get a lot of conflicting answers (no offence to anyone who has offered me advice) and I don't know enough to decifer it all. I am learning a great deal though digging into it and doing my research. My mom has been living with me for the past two years with the help of a care aide. She has advanced stage dementia and went into a care home last week. I now have the time and soon enough the money to get this lathe up and running and I want to do it right the first time to save any frustration in the future.

RE: Electrical question - Shawn - 02-19-2015

Here is a question I'm curious about. The work light on my lathe has its own transformer rated for 380/420v input and 50v output. If I ran 240v into the transformer would it still output 50v or would it be a fraction of the input?

RE: Electrical question - Hopefuldave - 02-19-2015

Hi Shawn,

I'll repeat myself! You CAN run it from 220-240V 3-phase from a VFD, just rewire to delta (U2 to V1, V2 to W1, W2 to U1, 220v 3-phase form the VFD to the three joins) connection - I've done this plenty of times!

Remember you can't have any switchery between VFD and motor and you'll need to wire the lathe's switchgear to the VFD's low-voltage control terminals - many VFDs will be configurable to either maintained contact or momentary contact switches for start/stop/reverse etc. - I've done too much of this, so if you need a bit of help PM me (I'll probably need a copy of the lathe's original wiring diagram and the type of VFD you're using, though) - it can't be as hard as my Holbrook! (pic of its original electrical panel attached...)

The 1024VSL has a mechanical variable-speed drive, so yo don't NEED the VFD's variable speed features, but they still have advantages, those nice gents in China sell high-power resistors (the ones in aluminium extrusions a foot long) quite cheaply, used for dynamic braking which is a very nice feature (assuming your VFD has "brake resistor" terminals, not "brake unit" - read expensive and specific to the VFD), the VFD can be set up to give a very low "jog" speed (mine gives 1/10th the set spindle speed, so as low as 2 RPM to a max of 150, depending what's set on the gearbox/speed levers) for setting up and weird operations - I could go on, being an electrical type I've even come up with a near-constant surface speed setup so spindle speed is controlled by tool position and speeds up as you approach the lathe axis to get more consistent finishes when facing and parting, it goes on and on...

The 380v lighting transformer will only give around 24 - 30v instead of 50, so on mine I fitted a 12V halogen lamp and holder, put in a cheap low-voltage lighting "electronic transformer" run from the 240v before it gets to the VFD (UK mains voltage is 240 everywhere on single phase, 415 3-phase) - I'm pretty sure you could get a 110v input version in Canada for a few dollars. I'd avoid compact fluorescent and LED lamps as they can "strobe" and visually freeze the spindle - until you stick your hand on it! Worse, the colour rendering's all wrong...

The coolant pump could be 3-phase like the spidle motor, if so it's worth checking how it's wired inside the connection box - mine was star-wired so I swapped it to delta and added a small, cheap VFD not much bigger than a cigarette packet (it only needs about 150 watts) to allow varying its speed for different coolants (soluble-oil suds, neat cutting oil, kerosene etc.) but you can cheat with a small motor-run capacitor from one phase to the "vacant" phase and it'll run adequately, a bit like a static convertor (search on here for those).

That Smart and Brown is a pretty good lathe, proper English Toolroom kit, if all you've been used to is far-eastern hobby machinery it should be a revelation :) Next step, a Holbrook ;)

RE: Electrical question - Hopefuldave - 02-19-2015

AArgh - didn't attach the pic!

The original electrical panel - yes, all that exposed metalwork's at 415v, luckily it hides behaind a boted-shut door in the end of the lathe base (the door weighs nearly as much as a Chinese minilathe...)

And the update, before installation:

The update is needlessley complicated, I'm like that...

RE: Electrical question - Shawn - 02-19-2015

Thanks Dave I really appreciate the help. It's funny that I was just talkin to a guy the other day about his Holbrook model C-16 that he has for sale. Maybe if I'm successful with the S&B I'll decide I need another English lathe?