Bridgeport Motor Replacement or Fix

[bcfoster89]

Thanks for all the input, all very good points! So I checked the resistance between each phase (at the switch) and got 7ohms between them (not sure what it's suppose to be but they were all the same). I also checked the resistance between each phase and ground and all were open circuits, so I'm assuming I didn't damage the motor enough to short any windings.

Based on everyone's feedback, since I already have the VFD (currently running my old Hoefer drill press) I think I will hook it back up to the Bridgeport and see how the motor runs. I think this will prove if the motor is ok and if it's a motor or SPC issue. Attached is a drawing of the SPC wiring (including internals based on looking inside, I have since added another capacitor per the manufacturers suggestion) and pictures of the motor and switch box.

I'm out of town till Thursday but I'll try the VFD when I get back and give an update. I've read through many VFD posts but are there any extra safety precautions I need to take with wiring it? I have the basics like properly sized breaker and wiring, common ground point, VFD in an enclosure, and only using the VFD to control on/off.

 

[mksj]

You should be good to go if using the VFD with with you describe. The VFD motor output should be directly wired to the motor and not run through any switch gear. I would recommend adding a remote switch for the lathe direction, if two wire control then a 3 way switch where the center is stop, this will be connected to the low voltage VFD inputs. You can also use what is called 3 wire control (which I prefer for the mill) which is a a NC momentary button for stop, a a momentary NO switch for run and a sustained 2 way switch for forward and reverse. If the power drops out for any reason with 3 wire control will not restart. Some VFD's also have a program parameter to prevent the VFD going to a run command on power up, that can be used for 2 wire control.

Older motors can have issues with insulation breakdown when using a VFD, but usually this is more of a problem with longer cables and if you were using the motor on the higher voltage windings, which you are not. High VFD carrier frequencies can increase insulation breakdown so I would use 6kHz or below for the carrier frequency. Given the 1 Hp rating I would not run the motor below say 30 Hz nor above 75Hz, if you have a reeves drive then leave the motor at 60Hz and use the mechanical speed adjust. If there is something you do not follow in the VFD install or programming, we should be able to help you further.

 

[markba633csi]

Just to clarify: In your first post when you said "it began billowing white smoke" was that from the mill motor or the phase converter?
-M

 

[bcfoster89]

Just smoke from the motor, the phase converter seemed fine. I removed the motor and it still spins fine, so bearing seen ok. Also, no electrical shorts. I have the vfd set up for 3 wire control so I'll be testing it out soon and report back. Thanks for all the input!

 

[bcfoster89]

I was able to get the VFD hooked up and ran the motor on the bench. No smoke! It actually ran extremely quiet and smooth. There was a little burning smell but I'm hoping it was just residual. Next I'll pull the motor cover off and clean it the best I can then try to run it again on the bench for 20-30 min. If it seems good I'll reinstall and assume it was the SPC that was causing the problems and keep it running on the VFD.

 

[Eddyde]

Be careful of what you use to clean the motor, some sprays like brake or carb cleaners can melt the lacquer off the windings. CRC makes a product called "Lectra-Motive" Electric Parts Cleaner. I have used to clean old motors and it did no harm to the windings or any other parts, works great too.