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3 phase Bridgeport wiring
- Thread starter ngng
- Start date
- Replies 16
- Views 387
JohnEvans
Titanium
- Joined
- Sep 23, 2009
- Location
- Phoenix,AZ
Yep !
Thanks for the sanity check. Glad I double checked this guy's work. He showed me a single phase 220 outlet...and I said...hey, I don't think that's right. But, what do I know
Bill D
Diamond
- Joined
- Apr 1, 2004
- Location
- Modesto, CA USA
Correct and to reverse you just interchange any of two hot leads leaving one alone. In my very limited experience all three hot leads are the exact same black color insulation. Green or bare wire for ground. Overseas can use brown or yellow for ground, sometimes.
Bill D
Bill D
William Payne
Aluminum
- Joined
- May 29, 2016
In my part of the world which may be different the only time neutral is involved for 3 phase is when there are single phase components on a 3 phase machine. Your guys way of doing things may vary.
Cole2534
Diamond
- Joined
- Sep 10, 2010
- Location
- Oklahoma City, OK
Be careful, sometimes one leg has a higher voltage than the other 2. Best to put a meter on your incoming wiring to see what you have phase to ground on all 3.The Bridgeport manual wasn't super handy. It basically told me to be a qualified electrician
Joe Gwinn
Stainless
- Joined
- Nov 22, 2009
- Location
- Boston, MA area
Four wires: Three hot wires (black in the US) and a safety ground (green) is a Delta configuration.The Bridgeport manual wasn't super handy. It basically told me to be a qualified electrician
Five wires: Three hot wires (black) and a neutral (white) and a safety ground (green) is a Wye configuration.
Both configurations are found in the wild.
Doozer
Titanium
- Joined
- Jul 23, 2001
- Location
- Buffalo NY
A 3 phase motor needs 3 phases.
Grounding the motor case is a really good idea.
Not sure why people are so concerned
with a neutral. And why people are concerned
about a wild leg. Not sure why the concern over
delta feed or Y feed. The motor does not know.
-Doozer
Grounding the motor case is a really good idea.
Not sure why people are so concerned
with a neutral. And why people are concerned
about a wild leg. Not sure why the concern over
delta feed or Y feed. The motor does not know.
-Doozer
nt1953
Hot Rolled
- Joined
- Sep 4, 2004
- Location
- Huntsville, Alabama
If there is any possibility that the motor is rewound, then I would take it to a motor shop to verify the wiring. I let all the magic smoke out of my Bridgeport clone's motor when I wired it according to the wiring diagram (shown in two places on the motor). When I had it rewound, I did not leave the shop until they told me how it was wired. It turned out that they did not wire it according to the wiring diagram either. If I had just wired it up again and turned it on, I would have let the magic smoke out of it again.
Not related to my machine, but what's the neutral for with three phase? I thought those motors don't need it because of the three hots alternating?
Why would somebody "rewind" a motor? I know the original owner, so I can ask.
My understanding is the machine does not need a ground. The ground is so humans don't die. There is a ground on the motor case and it looks like it's wire to the ground on the plug so we should be good there.
jim rozen
Diamond
- Joined
- Feb 26, 2004
- Location
- peekskill, NY
" but what's the neutral for with three phase?"
The original question involved a "CNC" machine. Those might have small 120 volt loads involved. They may or may not run those via a small transformer in the machine.
The original question involved a "CNC" machine. Those might have small 120 volt loads involved. They may or may not run those via a small transformer in the machine.
Jim Kennedy
Aluminum
- Joined
- Mar 16, 2008
- Location
- Marulan N.S.W. Australia
If in Australia and the machine is 415v and the contactor coils are 240v a neutral would be needed.
Jim
Jim
Last edited:
Joe Gwinn
Stainless
- Joined
- Nov 22, 2009
- Location
- Boston, MA area
It's to handle unbalanced phase loads, which some motors have. The neutral carries the unbalance current. Otherwise, balance will be forced by conservation laws.
It's also true that a Wye connected motor will continue to spin even if a phase connection is broken, because the motor still has a rotating magnetic field. (This may or may not be a good thing.) With a Delta connection, if any phase connection is broken, the motor won't start, seeing only a single-phase drive.
As others have noted, you always want the safety (green) ground firmly connected to the motor frame, so if a motor winding shorts to the frame, it will pop a breaker, versus popping an operator. As I've said many times, the electrical codes are written in blood.
Joe Gwinn
Stainless
- Joined
- Nov 22, 2009
- Location
- Boston, MA area
I couldn't recall the name, but delta and wye motor connections were common, in particular for two-speed motors found on many machines of the 1970s to 1990s. This PM thread has the details:
https://www.practicalmachinist.com/forum/threads/12-wire-motor-delta-connection.407926/
https://www.practicalmachinist.com/forum/threads/12-wire-motor-delta-connection.407926/