[Techbuilder]

Hi everybody I need a little help
so basically I bought a used Bridgeport mill 1968 1hp
and my outlets at my shop are only 110v 20 amp
now I know it sounds like I should have 220 but I don't you see
my shop is like a mini where house kind of thing 110v 20amps is the most you can get in you mini warehouse. I talked to the electrician and he said the breaker is full so again 220 is not an option he said it him self.

So my question for you is how do I power a 220v 3 phase Bridgeport with 110v 20 amps?
Would one of these work?

Adjustable Frequency Drive, Teco VFD, Phase Converter, Variable Phase Output

[vger]

You could change the motor possibly....

[3944r]

Hello,

Yes you can. The TB Woods VFD's on the dealers electric site recommend a
20 amp fuse for circuit protection. I have the manual and I just looked up the specs. Im sure the Teco units are similar, but I don't have the manuals for those so I can't be 100% positive.

I would recommend the unit with the built in braking resistor, SW1C1S010H02 its the same price as the 2 without.
Its a bit bigger in size (due to the resistor) and you could argue the merits of having a braking resistor on a mill, but it will stop the motor super fast, and you may want to use the VFD on something else in the future (lathe, disk sander, etc) that would be something that could use an external braking resistor.

At 20amps, this may mean that using other electrical devices while you are using the mill may not be possible without tripping the circuit.

You could spend a little extra and get the Teco with the speed potentiometer, I bought one but in the end I set up a remote panel to control speed and direction anyway, it seemed much neater.

here's a thread to show you what I mean

Show us your VFD remote controls ! - The Home Shop Machinist & Machinist's Workshop BBS


regards


carl

[sch]

The 115V input VFD appear to be the basic VFD, not the newer sensorless
VFD which punch up the output at lower frequencies so as to maintain
the motor torque. The addition of the braking resistor basically allows
a faster transition from forward to stop or reverse, eg for power tapping
with out a tapping head. The basic vfd can't do this in less than 1-2sec.
I have used the FM50, it is 'old tech' but quite satisfactory. The other
VFD with the resistor is cheaper, but also 'old tech'. No big deal as
sensorless doesn't seem available in 110vac input devices on cursory
search and adds 30-50% to the price. $106 is a steal. The pictured
control setups in 3944 referenced threads are a good idea, about the
way mine is setup. Plan on a freq range from 30 to ~75 herz from the
VFD. My FM50 will go upto 120Hz or so but the motor doesn't like it and
the VFD trips out at about 80Hz. Below 15 Hz you can grab the spindle
and brake it down by hand. Motor cooling can be problematic below
30hz if run for a long time.

[3944r]

Hello CNCmakers,

Respectfully, I think you need to explain why you think an isolation transformer is necessary in this application, Where it goes in the application (input side or output side) and how much benefit this will give on a 115v/60hz $106USD drive........

sch, couldn't agree more, yes, it is somewhat 'old school' technology, but then there are real old school VFD's that have no motor overload protection and also use gate turn off thyristors that really need isolation transformers.

Sensorless vector would be great on any application like this, better yet closed loop, but given the cost of the drive, I don't think the OP can do much better.

There is a voltage boost parameter on the tb_woods drive that will go to 25% of rated motor voltage, this will help with low speed torque, but as sch said motor cooling can become an issue if used for long periods at slow speed

I have included a hookup schematic from the manual, substitute the three phase input with single phase.



regards


carl