Electrical question

[Hopefuldave]

The C10-13-16 are very nice lathes, but if you have your druthers (and your shop floor can take it), go for a model H - you can see one one youtube (not in action, sadly) if you search "mighty Holbrook" - they DO need 415v x 50Hz/480v x 60Hz though, as they are quite demanding (10HP) on power... they have the threading trips/stops, leadscrew reverse "on-the-fly" etc, which the model C doesn't - although I'm working on that! A model H is probably the only lathe that could turn my head, the machine shop at work may have to get rid of one soon, too...

The 1024 is also a cut above the average, even for English toolroom lathes, I suspect you're going to love it!

For my C13 I had to hack a 415v-in VFD to fool it into thinking it had the right supply when it was really getting 240v single phase (actually pretty simple when you know how) as the 3-speed motor is 415v only - no way to rewire it for 240 for less than the price of the lathe(!) - and is part of the Holbrook experience :)

Once hacked and installed, I have 2RPM - 2500RPM available. a combination of the lathe's 12 speeds (3 speed motor x 2 speed clutch n' brake box x 8:1 backgear) and a 5-85Hz VFD, from the original 22 - 1500RPM - the ultralow speed is useful for things like milling with a toolpost-mounted spindle (although it can "cog" a bit), the highest speeds for small work in aluminium.

Should you be as daft as me and use the VFD at very low frequencies (30Hz and below particularly), it's worth fitting an external fan to the motor for cooling, espacially if you're loading it much - if I remember right, airflow through a fan is proportional to the square of the speed, so at half speed it's only getting a quarter the cooling air - in my case, at 5Hz it's getting a hundredth... recipe for an escape of Magic Smoke from the motor! I recently struck lucky in the skip at work, Papst 10-inch cooling fans replaced as preventative maintenance in standby equipment that's used twice a year for half an hour to make sure it still works... 2011 date codes on them, and about 3-4 hours runtime total! A bit of adaptation's required though because they're metric, the fixings are on a 254mm diameter circle, not 10" like the Holbrook's motor... ;)

ANyway, enough of me digressing (it's the medicinal alcohol, probably), best of luck with the S&B, senda PM if you want any hints and tips :)

[Mayhem]

It is when following posts like this that I forget that I take my three-phase supply for granted.

[Shawn]

I would love to have 3 phase into my shop, count yourself lucky. So when I wire the motor for Delta will I need a VFD that is rated for twice the HP of the motor? It's a 3hp motor but I'm having issues trying to find VFDs rated for 6-7hp. 3hp vfd seem quite plentiful and rather cheap.

Shawn

[Dr Stan]

I'm running my 5 hp 240V 3 phase Logan with a Phase Craft RPC I bought on Ebay and I'm using a 10hp Lincoln 3 phase motor as the generator. I'm not a bad 2 wire electrician, but not versed in 3 phase and the guy who makes & sells these units was very helpful. You may want to contact him for some advise.

You asked about the 50Hz V 60Hz issue. Running it on 60Hz will simply make it run a little faster. You can determine how much by using a simple ratio formula.

Before you get the motor rewound to run on 220 3 phase I'd check the Surplus Center for a replacement motor. Often times a new motor is less expensive than rewinding. The one issue I do not know about is how running the lathe on 220V instead of 440V will affect the performance of the other circuitry. The light would be fairly simple to replace with a 110V LED machine/task light.

BTW, that's a very very nice lathe.

[Shawn]

Thanks Stan, I was hoping to bypass the RPC and use a VFD as I don't see needing more three phase power in the future that wouldn't be better served with a VFD. I have a Clausing 8520 and a 3phase 2hp motor that will eventually get converted but thats better off running on a VFD so I get the variable speed control.

Shawn

[f350ca]

If the VFD is rated for single phase input you shouldn't need to oversize it. The manufacturer has already done that. Think the over sizing thing was where you are using a three phase input VFD on single phase, there you'd be overloading the input diodes that supply the DC bus current.
Someone speak up if Im wrong.

[EdK]

(03-03-2015, 01:39 PM)f350ca Wrote: .... Think the over sizing thing was where you are using a three phase input VFD on single phase,...

That's correct Greg.

Ed

[Shawn]

This all sounds simple enough, rewire the motor for Delta and buy a VFD. I'll be ordering the complete manual and wiring diagram from Tony at Lathes.com for this lathe. I'm hoping that I can simply disconnect the lamp and coolant pump from the main electrical system and deal with them both individually, most likely a conversion to 110VAC

Any thoughts on the different VFD's available on Ebay? There are generic units for less than $200 delivered or something like the Hitachi units that will be close to $500 delivered. I don't mind spending the money for a more expensive unit if I need it or it has certain features I might require but to be hones I have never seen a single post from anyone complaining about the cheaper VFD's that are available?

Generic VFD on Ebay

Hitachi

Any thoughts or suggestions regarding these units would be appreciated. 

Shawn

[EdK]

Shawn,

I'm a big fan of the Hitachi VFDs. They are the cream of the crop in my opinion. If you'd like to spend less then my recommendation would be one of the Teco VFDs. I've got a Hitachi on my mill and have had no problems at all with it. Hitachi's manuals seem to be better written then other brands. I bought a Teco for the lathe, which I haven't installed yet.

Talk to member SteveC about the cheap VFDs from ebay.

Ed

[f350ca]

I've only started trying to figure these out so I know enough to be dangerous. But i'd go for the one behind door two. It states it uses sensorless vector technology, I think you want that, from what i understand the processor measures the phase angle between the current and voltage on the load, essentially power factor, to determine if the motor is lugging down below its synchronous speed. It then boosts the voltage or current or frequency, not sure which to give the motor essentially constant torque below 60 hz. Better more expensive systems put an encoder on the motor and feed that back to the vfd to do the same thing.
The first one says it will work on single or three phase input, (no real specs) but Id expect that to be one you would need to under rate with single phase input and only run a 2 hp motor with it.
I want to use one on a bowl lathe so I've been trying to learn what I can. My buddy that owned an electrical company that specialized in factory automation was my go to guy for stuff like this. He left the country or something? One of his employees is running the show now. Have stopped by a couple of times but he hasn't been around. If I catch him in the office we should be able to get the real story, not opinions off the net, like mine of course. It was him that leaned me to the Phase Perfect solid state 3 phase converter I have now. He was right on that one.