# More Bridgeport electrical advice required

• posted
Okay, rewinding what I have is NOT (\$\$\$) an option.
From my previous post:
There are 9 wires coming out of the motor, with metal number tags.
1,2 and 3 all separate, I assume went to the reverse switch, which is
not there.
4 and 7 tied together
5 and 8 tied together
6 and 9 tied together
This allowed it to run on our 460 3 phase at the shop.
Will this drop it to 230?
1 and 7 tied together, use as L1 input
2 and 8 tied together, use as L2 input
3 and 9 tied together, use as L3 input
Tie 4,5 and 6 together, insulate and tuck away.
If this will work, then I can get a 230 volt input VFD, waaay cheaper
than rewinding my motor.
Being as how I have no diagram for the motor, I looked at a LOT of
pictures & web pages, and it looks like my current wiring is pretty
standard for a 460v 3 phase motor, which matches the motor plates I
looked at, which had Hi and Low wiring diagrams, which is where I got
the above possible solution for my Low wiring.
• posted
It is 9 lead and was connected high voltage wye then...
Yes, and in doing so, you will be connecting the second set of wye windings into parallel operation with the first, whereas they previously had been connected in series with each other= low voltage wye.
If all 12 leads are brought out to the peckerhead then a person can connect either as delta or wye on a whim...and there also exist various "soft start" and "wye delta shift" scenarios that can be user-incorporated...
--but if there's only 9 leads then whether it is delta or wye depends upon internal connection.... and without knowing how it was previously connected, you would need to run continuity test in order to be sure--ans so here is a diagram one can use to do that with:
Note on the wye internal connection, the only place lead #1 only rings out to is at #4, whereas with the delta, #1 rings out to both 4 and 9
• posted
OOPs it could also be it was connected as high voltage delta as the connection is the same regardless...
Unless it was connected as high voltage delta, in which case, see the below as the only way to tell them apart is to test continuity as I had explained in my previous post
• posted
Thank you very much. I'll get the Fluke out tomorrow & check it out.
All the more so me, as up until now my only knowledge of three phase was, "don't F*** with it, get maintainence".
Wanna recommend a 2 HP VFD? I'm guessing that will be good enough for my needs. Also, will I be able to reverse while tapping with a VFD?
If a VFD will work, I'll probably just set it up to run the motor at it's rated speed, and use the step pulleys for what I need, as it's just a hobby mill for home.
• posted
Simple stuff really.
Look for a 1 HP VFD that is rated for single phase input. VFDs that are rated for single phase input do not need to be de-rated / oversized when running from single phase. VFDs that are not specifically rated for single phase input do have to be de-rated / oversized when running on single phase input. A few VFDs, typically fairly high HP ones will not run on single phase input at all. A few smaller VFDs are actually single phase input only. You don't need a fancy unit, just a basic model will be fine for a Bridgeport.
• posted
As to speed, motors can fly apart if run too fast basically meaning that anything above say 20% over rated and all bets are off.
On the other hand, slower speeds are okay BUT for short periods of time ONLY....
--reason being, lack of cooling air flow volume will cause the motor get hot unless you add an auxillary fan to it.

• posted
WRT speed, on my Bridgeports I never overspeed the motors. What I typically do is leave the belts set at or one down from top RPM and use the VFD to slow it down as needed for what I'm doing, typically 30 or 45 Hz. Since I'm not normally taking cuts heavy enough to need full HP, this works fine. For the odd time I really need the HP I'll run the motor at 60 Hz and adjust the belts and/or back gear. For manual hobby milling the duty cycle is low so heating isn't a problem.
• posted
I don't believe he has a 2 HP motor, if he has a step pulley head it's going to be a 1 HP motor.
Capacity, not efficiency, and that's only if the VFD is rated for 3 phase. Many smaller VFDs are rated for single phase input and require no upsizing. Some smaller VFDs are single phase input only.
• posted
[ ... ]
Yes! I posted similar advice earlier.
Yes. Just make sure that your VFD is one which can run from single phase input -- and rate it a bit higher than the motor to make up for the lack of the third input wire.
It is a very common way to set up dual voltage three phase motors in the USA. UK motors appear to have 6 wires, and you get one (higher) voltage by wiring it in Wye format, and the other (lower) voltage wiring it in Delta format. But these voltages do not go in a double/half relationship.
Enjoy, DoN.
• posted
[ ... ]
[ ... ]
This depends. Since the same rotor is used in 2-pole, 4-pole, 6-pole, and likely other motors -- if the rated speed at 60 Hz is 1800 RPM (actually slightly less) or lower, don't worry. Only worry if the rated motor speed is near 3600 RPM (3500 or 3550 likely) -- which means that it is a 2-pole motor, and a VFD set to above 60 Hz will be running it faster than the design speed of the rotor. I doubt that you will find a Bridgeport with a 2-pole motor.
Looks like your nameplate says 1740 RPM (a bit under 1800 RPM, so it is a four-pole motor, and should be safe at all VFD speeds -- though whether the drive belt will be happy is a different question. :-)
Enjoy, DoN.
• posted
You do not have to oversize a VFD that is *rated* for single phase input. Some smaller VFDs are single phase input only.
• posted
Got the Fluke out, & checked continuity on all wires, after unconnecting these 3 pairs that were connected: 4-7, 5-8, 6-9.
Got continuity on: 1-4, 2-5, 3-6, 7-8-9. This corresponds to high voltage "Y" winding on the picture.
New 230v wiring will connect:
1-7 to T1 2-8 to T2 3-9 to T3
4-5-6 tied together and tucked away.
Gonna order the VFD Friday. Hope the smoke stays in the motor.
Hitachi X200-007NFU1 from Drive Warehouse. \$159 plus shipping from Dallas, TX to Muskegon, MI.
Thank you very much, once again.
A friend of my brothers just bought a Bridgeport, he's gonna build a rotary convertor, I think he's gonna be a little envious.
• posted
>>
Small basic VFDs are at the point they are cheaper than building a rotary converter if you put any value on your time. They are also quieter than a rotary converter and of course give you variable speed, soft start and braking that you don't get with a rotary converter.
• posted
Yup you pretty much nailed it.
If there is contactors with heaters in them then the elements will need to be swapped out for low voltage operation--any fuses probably will need swapped too.
I would guess allen bradly or westinghouse contactors--if so, then charts showing the correct part number should be easy enough to find online.
• posted
Rotaries can generate quite a bit of unwanted heat in the summer time.
• posted
Thanks, I forgot about that. There is a contactor on the side of the mill, with a separate on/off switch.I'll have to get a 230v setup to replace it.
• posted
>>>
Perhaps an extra warning is appropriate: *** DO NOT SWITCH THE CONNECTIONS BETWEEN THE VFD AND THE MOTOR ***
If the motor leads should connect directly from the motor to the VFD, no switches, contactors or starters in that circuit. Switching the leads between a motor and VFD under power has a good probability of blowing up the VFD.
All start, stop, forward and reverse functions have to be controlled through the VFD. You can use the front panel controls on the VFD for this purpose, or you can wire the original FWD-OFF-REV switch on the machine to the VFD's control inputs to make it operate "transparently". I've done this on one of my Bridgeports and will do the same on the other soon.
• posted
Thanks. I have already gotten the manual, and read all the safety warnings. Lots of them.
• posted
A lot of this is urban myth. I have no problems at all with doing this. The three phase supply to my shop is provided by a 23kVA VFD...
Mark Rand RTFM
• posted
Mark Rand fired this volley in news: snipped-for-privacy@4ax.com:
Joke, right? A lot of this ISN'T urban myth, too. MOST small VFD's documentation warns against connecting and disconnecting the load while powered. It has to do with reverse EMF caused by any inductor's being switched rapidly.
Besides, the average machine might have a 3.5KVA-7KVA unit driving one motor. Yours is a monster by ordinary perspective, and it might even be designed for that specific duty.
LLoyd

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