What's new
What's new

Single phase hobby shop advice for implementing 3 phase 220 vs 440

S_Minion

Plastic
Joined
Mar 29, 2018
Got some 3 phase equipment that followed me home, and needing to upgrade the electrical in my shop to run it.

The main concern is powering the lathe:

American 1610 Lathe 15HP wired for 440 currently

I would say over time I would plan to acquire additional machine tools, but likely just a Bridgeport, maybe a larger compressor. This would just be me building things for "fun" so not a production setting.


Other parts I have that are relevant

25KVA dry transformer 440->220 single phase (qty 3 available)
50HP 3ph motor
25HP 3ph motor
7.5HP *1200 rpm 3ph motor

My shop was built by me with 200 amp dedicated single phase service that is wired up to welder/compressor/plasma outlets in various locations. I am comfortable with doing any of the wiring, but the 440 has me a little apprehensive. All the 600 volt rated parts seem hugely expensive and less available outside of 9:5 commercial supply house, plus the perceived arc flash goblin.

The potential setup I am thinking of running based on the parts I have acquired:

100 amp circuit -> back feed transformer -> Fused disconnect -> DIY 440 volt rotary phase converter with 25 HP motor -> 440 volt power distribution as
needed.

Slightly worried that the 25HP might not be enough to start the lathe, but I think I would rig it up pony started to just to try with no caps etc first.



Am I better off to rewire/repower the lathe to 220V seeing as I do not need the HP? I would just switch it as is, but the internal wiring is only 10 awg so I feel like I would have to drop down to a 7.5 HP motor maximum to not have to completely redo it. The main contactor says 15HP @ 220V

Is there a perceived advantage to having 440 3 phase available vs 220V? Cheaper machines at auctions etc? I understand the smaller wire gauge for power distribution, but is that really it? I don't feel like I will "need" it for anything I can think of but I am just getting started on machine tools...


What would people that have likely changed setups several times start with? 440 single phase and VFD everything? 220V rotary converter? Full 440v panel setup with RPC? simple rpc pony started?


Thanks!
 

Dan from Oakland

Titanium
Joined
Sep 15, 2005
Location
Oakland, CA
My advice would be to keep things at 220V. The chances are you will never load a machine tool to full capacity, or if you do, it will be for very short periods. You may already be aware of this, but as an electrician friend told me long ago, 220V might kill you but 440V will kill you. Nuf said about that but why complicate things with 440 when most likely 220V will do everything you need?
 

DaveKamp

Titanium
Joined
Oct 3, 2004
Location
LeClaire, Ia
The advantage to going higher voltage, is lower power loss and ability to go smaller conductor cross-section, but the disadvantage becomes insulation resistance ratings and code compliance.


I would split the difference:

Remove the mag starter from the lathe, leave it wired for 440. Install a 440vfd on it, but go to a larger size if you can. Use an older type, one that isn't extremely 'smart', or one that's certain to have the ability to disable phase-loss-detection. Mount a 10kva 120/240:480 transformer in the belly, bring in the 220 through a fused disconnect switch and then a power contactor controlled by the start-stop buttons on the machine.

Set up the VFD to power the spindle motor, set the VFD with a gentle ramp-up, dynamic braking, etc., as best for the lathe.

By doing this, you take advantage of the existing power arrangement, have the ability to tap into a huge market of dirt-cheap, industrial-quality second-hand VFDs in that power range, you get soft-start, and many other operational features of VFD. It also means (since your transformer primary is 120/240, you can tap off the 120 winding for worklighting, additional controls, etc)

The downside, is that you need to find more dry transformers of 20kva and down. They're not hard to find, and not expensive, once you find how to search local businesses, scrapyards, and auction companies. It also means your machine is 'portable' within a common power system, and if an insurance inspector every wanders in, there won't be a 480v transformer buzzing away along the wall.
 

Ohio Mike

Titanium
Joined
Oct 30, 2008
Location
Central Ohio, USA
My advice is to try to stay with 240 3 phase. So far I've been able to stay that way. Fortunately the new shop has 240 volt delta 3 phase service from my utility but I lived with an American Rotary RPC for years. If and when I need to I will add a transformer and sub panel.
 

motion guru

Diamond
Joined
Dec 8, 2003
Location
Yacolt, WA
Run RPC at 240V. If you have a 3-Phase transformer that is 460:230 rated, connect it to the RPC with a contactor and then you have your choice of 230 or 460 three phase and typically you can balance voltages extremely well with a multi-tap transformer.

I ran this setup for 7 years and liked having the ability to power equipment up at whatever voltage it came setup for. This also allows for purchasing cheaper used 460V VFDs at the appropriate rating for the motor.
 

S_Minion

Plastic
Joined
Mar 29, 2018
I had been looking closer at it and its not going to be so bad to rewire, mainly just fuses and 30-40 ft of 6 awg, so I am headed that way. Should have enough parts to start work on it this weekend.

Thanks for the tip on the heaters, did not know those were a thing being a 3phase machine tool noob. One location is bypassed with a wire that looks original, or at least quite old. I bought a pack of heaters, enough to put all 3 in and still have a spare. Or would you just leave only 2 as it is still protected that way and 1st location would cover me if the rotary converter lost the 3rd leg.
 

Phil in Montana

Stainless
Joined
Jul 31, 2007
Location
Missoula Mt
Something that is always overlooked, leave your 15 hp wired for 480 but feed it 240, the motor will not be eff but it will act like a 5 hp and will be more than enough power for a hobby shop, without all the amp draw...Phil
 

BT Fabrication

Hot Rolled
Joined
Nov 3, 2019
25 hp is fine to run it.

I personally went RPC then step up to 600V. its much cheaper to run T90 wire at 12GA 100 ft then 6GA.
Just need a 3 phase distribution panel, which aren't cheap.
 

thermite

Diamond
Just need a 3 phase distribution panel, which aren't cheap.

I have three, bought brand-new, but with a bit of shopping around for "NOS". So they were near-as-dammit the same cost as 1-P load centers. About a hundred bucks for a 30+ position Square-D with one 100A breaker and the appropriate type of cover, IIRC?

What was NOT as "cheap" as 1-P one and 2-pole breakers was the 3-pole common-trip Square-D "QO" breakers to POPULATE the bugger!

OTOH, I only have to doo this ONCE, and only a few circuits, so it may as well be "right".

:)
 

drcoelho

Stainless
Joined
Feb 19, 2017
Location
Los Altos
Ditto for going 240V 3 phase. In my shop, most of the machines run off 240V 3 phase, but 3 of them from Europe run off 400V 3phase, so I just use a step-up transformer to handle those machines.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
American 1610 Lathe 15HP wired for 440 currentlyAmerican 1610 Lathe 15HP

25KVA dry transformer 440->220 single phase (qty 3 available)
50HP 3ph motor
25HP 3ph motor
7.5HP *1200 rpm 3ph motor

What do the lathe controls look like for going from 440 to 220? The 440 motor is the easiest thing to change for 220 if it is dual voltage 440/220.
Is there an internal transformer inside the lathe cabinet that down converts 440 to 220? Then it's 220 all the way.

Otherwise keep the 440 stuff inside the lathe, use the 25HP 220V RPC followed by your 220 to 440 transformer to power the lathe.

What you ask is something that comes through here many times.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I had been looking closer at it and its not going to be so bad to rewire, mainly just fuses and 30-40 ft of 6 awg, so I am headed that way. Should have enough parts to start work on it this weekend.

Thanks for the tip on the heaters, did not know those were a thing being a 3phase machine tool noob. One location is bypassed with a wire that looks original, or at least quite old. I bought a pack of heaters, enough to put all 3 in and still have a spare. Or would you just leave only 2 as it is still protected that way and 1st location would cover me if the rotary converter lost the 3rd leg.

You will need to change out any relay and contactor coils from 440 to 220 as well, unless the is a internal 440 to 220 transformer that can be bypassed.
 

S_Minion

Plastic
Joined
Mar 29, 2018
You will need to change out any relay and contactor coils from 440 to 220 as well, unless the is a internal 440 to 220 transformer that can be bypassed.

The lathe controls all run on 110V, and there is an internal transformer for that, and another for a 110 light circuit as well. They have configurations for both 440/220 volt input. All of the motors are dual voltage as well main/rapids/coolant so just need to change them to the low voltage configuration. So I believe I am pretty well set there.

Did make another rookie mistake the 50 amp FRS fuses are a larger physical size than 25 amp fuses so I had to get a 'new' fuse holder.
 

S_Minion

Plastic
Joined
Mar 29, 2018
So to update this thread I started working on setting up a pony motor to spin the 25HP motor up.

Got it going on the floor and flipped the breaker on. Lights dimming, loud hum, and molten copper sparks shooting out of the motor. Breaker pops as I am switching it back off, maybe 3 seconds in. Start ohming the motor leads out, and there is low resistance to the case on all the phases. Maybe should have checked that a long time ago. Open it up and the windings are REALY overheated/melted, so the motor was junk.

Fast forward a few weeks found the only inexpensive quasi local 25/30HP motor I could. Surplus brand new 25HP motor with a broken mounting foot. This motor is 3600 rpm and different shaft diameter so I source up a new pulley for it, the smallest I can find as my pony motor is 1750 rpm. Try it out with the pulley I had for the pony that ends up about 20% over drive. First time I pulled the pony motor before hitting the breaker, but the speed was not enough and the motor did not start. Second time left it running then hit the breaker and it spun up, minor light dimming.


Borrowed some measuring equipment so I could see what was really going on with it to verify it was ok.

3rd phase voltage is definitely a bit high ~200 volts/ground with nothing on there. Unloaded current draw is 20 amps. All of the individual motor leads match up within .1-.2 amps. Not sure if the unloaded amps seem a bit high, maybe because nothing is balanced yet?

Got a pulley to get the speed up on startup but my single phase pony motor (1/3HP) can't pull it once the start cap disengages and the rpm starts dropping. looked at it and it is just a rpm switch that disconnects the cap no different windings. If I use the other pulley I have it runs the motor to 2100 RPM. It seems to start fine from there every time I have done it, but the inrush was dimming the lights slightly. I did check the current and its in the 350 amps range for 0.6-0.7 seconds as it spins up.

The current waveform is a little interesting at startup.


20201224_224735.jpg20201224_222209.jpg
 

SomeoneSomewhere

Hot Rolled
Joined
Dec 24, 2019
I believe roughly 208V to ground is what you expect with these on the high leg. You want 240V line-to-line, and your ground is in the middle of two of the phases so the third one sits higher.

It generates the same setup as a high-leg delta supply.
 

jim rozen

Diamond
Joined
Feb 26, 2004
Location
peekskill, NY
To put it another way, don't bother measuring volltages to neutral or ground, only check line-to-line and optimize that for balance. You may want to upsize the pony motor a bit. Also be sure to put an amp-clamp on every wire in there and put the results here for discussion...
 

S_Minion

Plastic
Joined
Mar 29, 2018
Made some measurements the other day. It is a 12 lead motor so each current shown is per connection.

Going to see if it starts the lathe motor tonight.

3phase.jpg
 

thermite

Diamond
Made some measurements the other day. It is a 12 lead motor so each current shown is per connection.

Going to see if it starts the lathe motor tonight.

View attachment 308969

Up the 1-P 1/3 HP pony to 3/4 HP - I'd skip right past 1/2 HP - and yer probably good to go.

If I NEEDED a pony, I'd use a 12 or 24 Volt DC IC engine starter.

But that's only because I already have the dual-12V batteries kept always on float for the Diesel gen set and emergency LED's (no windows in my shop).
 








 
Top