# Bridgeport 3 phase motor - wiring



## dansawyer (Feb 16, 2021)

I have a Bridgeport 3 phase motor from a BOSS 8 CNC Series 1 mill. Someone had disconnected the motor wiring from the junction box and I am left with 9 wires. My plan is to wire the motor for 3 phase 220V. I will be using a 3 phase VFD.
My questions are:
1. Are Bridgeports wired Delta or WYE?
2. How can I sort out the 9 wires to the correct configuration and connect the motor to the VFD.
Thanks, Dan


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## hwelecrepair (Feb 16, 2021)

Wire nut 4 5 and 6 together.  1 and 7 will go to a leg(lets say L1), 2 and 8 will go to a leg (lets say L2), and 3 and 9 will go to a leg (lets say leg 3).

Jon


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## dansawyer (Feb 16, 2021)

There are no numbers. Are they Delta or WHY?


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## hwelecrepair (Feb 16, 2021)

Damn, that sucks.  Most Bridgeport motors have the numbers printed on the wires.  

Id send it to a motor shop to have them figure it out.

Jon


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## markba633csi (Feb 16, 2021)

You need to "ring out" the individual windings with an ohmmeter, then phase them, using a small transformer and the voltmeter
Details provided if you want to give it a go
-Mark


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## Lo-Fi (Feb 16, 2021)

I think details of that process would be most welcome for future ref anyway, @markba633csi . Yes please!


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## markba633csi (Feb 16, 2021)

OK will do,  need to go pick up some cat meds first
If anyone else has done this also, feel free to jump in
-M


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## Lo-Fi (Feb 16, 2021)

Belling out the pairs with a meter I've done, but the phasing with a lightbulb trick I'm interested in!


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## ErichKeane (Feb 16, 2021)

I used this video once (they have the Y one as well) and found it very helpful:


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## dansawyer (Feb 16, 2021)

Thank you. Are Bridgeports typically configured as WYE or Delta? 
I will be running the motor via a VFD, does that matter? Are VFD dependent on WYE or Delta or are VFD agnostic to WYE or Delta?


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## markba633csi (Feb 16, 2021)

The method in the video would work also, but using lantern batteries is an expensive way to do it- unless you have them on hand
I'm not quite sure I follow how he determines the polarity of the winding ends- I'll have to watch it again
-M


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## ErichKeane (Feb 16, 2021)

dansawyer said:


> Thank you. Are Bridgeports typically configured as WYE or Delta?
> I will be running the motor via a VFD, does that matter? Are VFD dependent on WYE or Delta or are VFD agnostic to WYE or Delta?



The VFD doesn't care which it is I believe.  I also believe that motors can be BOTH WYE AND Delta, with one giving 220v and the other a 440v winding.

You're best off looking at the data plate to figure out which it is.


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## Lo-Fi (Feb 16, 2021)

Star is often the higher 400 something volt config, delta for low 220 or so volt. VFD is often 220 volt output, so you'd be wanting delta config on the motor. The actual configuration is irrelevant, providing it gives the correct drop over each winding. In delta, there's only 1 winding between each phase. In star, there are two in series.

That being said, machine tools - and Bridgeport's are no exception - are often Dahlander wired, which is high volt, two speed. If that's the case, you may or may not be able to configure it for a 220v VFD without some internal reworking. You've got a fighting chance with 9, rather than 6 wires presented, but be prepared for some serious noodling. Is there a data plate?


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## markba633csi (Feb 16, 2021)

I thought the low volt delta config puts two windings in parallel per phase- no?
-M


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## Lo-Fi (Feb 17, 2021)

Yeah, I'm kinda simplifying there!


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## Bi11Hudson (Feb 17, 2021)

Not being familiar with the Bridgeport machine in particular, my thoughts shoul be taken with a grain, nay a shaker, nay a box of salt. Basically a disclaimer for everything. For general motor wiring, a motor with 12 leads can be wired normally Delta, or Wye, or both in a start/run configuration. The OP specifies specifically 9 wires, which would be more* likely *a Wte configured dual voltage motor. 

With an ohm-meter or test light, determine if there is/are *one or three "star" points*. One "star" point indicates a "Wye" motor. Three "star" points indicates a "Delta" motor. A "star" point is defined as one wire having a connection to two coils. More specifically, three wires having continuity. Actual "ohms" measured come into play only to determine which wire of the three is common.

I am an "old school" electrician learned in phasing out a motor using a lantern battery and a compass. There are many videos of other methods for phasing a motor. I highly recommend watching several before actually trying it yourself. Just to get a "feel" for motor winding.

.


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## Dabbler (Feb 17, 2021)

@Lo-Fi my BP motor was a hi/lo 220V/440V motor and I had no trouble wiring it to my VFD.. I wired it as low speed 220V and have had zero problems.

@dansawyer You should call around and find an electrical shop that will 'configure' your motor for 220V (high or low speed).  They should do it for about 40 bucks and test it on their 3PH supply to ensure it is right.  After that wiring it to your VFD is a no-brainer.  There are a lot of guys here that have VFD'd their mills with no rpobs, and can help.

It is nice to do your own phasing and configuring, but why take a risk on messing it up for 40 or 50 bucks?


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