VDF for a Bridgeport 2HP in residential setting

Hello I have brought home a Bridgeport 2HP milloing machine. I only have 240VAC single phase available.

It has a Varispeed head and it needs to be rebuilt as some of the components there are shot. Few hundreds of dollars for the parts, not a huge deal. However a VFD would allow me to change the speed of the motor too, even if it is considered detrimental to leave the Varispeed always in the same position as it would wear the assembly unevenly.

Any suggestions? I've read of people converting the Varispeed to a fixed pulley and use the VFD only. That would save a bit of money to pay for the VFD, but is it perhaps considered a hack job?

Any comment will be appreciated. I haven't used one of these machines in a good while, and most of my experience was on the lathe and the shaper anyway. Thank you

Depending on the work you perform this could be fine. However when you reduce speed with a VFD you lose HP.

Physical speed converters work a little like a transformer. A transformer (oversimplified) drops volts but increases amps so the KW is constant.

A variable speed drive (pulleys, gear boxes, etc) drops RPM but increases Torque so the HP is constant. HP is work performed over time. So if you slow down you have to do more work (torque) to make up for it.

A VFD (at best) is constant torque meaning you can perform less work at lower speeds.

All that said, like I said if you're not trying to max your spindle it may be fine, its how CNC mills operate for the most part.

A couple of alternatives to consider, a number of individuals use static converters, they seem to be OK in this application/mill, and they are inexpensive/simple to install. You loose about 1/3rd of the motor performance. An RPC might be an option if you have other 3 phase equipment, otherwise probably not cost effective.

You can use an inexpensive VF like the Teco L510, use it at a fixed 60Hz and continue to use the Vari-Speed head. The VFD would be directly connected to the motor and you switch the low voltage VFD inputs for the run commands. This way you will not get uneven wear on the mechanical speed system and keep it's performance advantage (preferred option vs. VFD speed control). If you had a larger motor on the head then a direct belt drive would be an option, as most digital (factory VFD/motor) mill heads these days operate this way. My mill is factory equipped as such and the frequency range is 20-200Hz using an inverter motor. High speed and back gear only.

yugami said:

Depending on the work you perform this could be fine. However when you reduce speed with a VFD you lose HP.

Physical speed converters work a little like a transformer. A transformer (oversimplified) drops volts but increases amps so the KW is constant.

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Yeah, that makes perfect sense. I knew the physics behind it (the comparison with a transformer is nice!). VFD's can keep (as you say, at best) a constant torque this means power will go down with RPM (by definition of power).

All that said, like I said if you're not trying to max your spindle it may be fine, its how CNC mills operate for the most part.

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Well, at this point - I have to find the right balance and the best compromise. It is true that I do not really plan to max out the specs of this machine. However:

- modification of the machine to be "single mechanical speed" and VFD-only might be more complex than a simple rebuild of the varidisc assembly.
- The modification might in principle be cheaper but will likely be detrimental to the "value" of the machine and impose limitations on the low-RPM power.

I believe I will just proceed and fix the varidisc and then get a VFD; I will make sure to change the mechanical settings to provide even wear on the machine.

mksj said:

A couple of alternatives to consider, a number of individuals use static converters, they seem to be OK in this application/mill, and they are inexpensive/simple to install. You loose about 1/3rd of the motor performance. An RPC might be an option if you have other 3 phase equipment, otherwise probably not cost effective.

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Not familiar with the advantages of RPC - right now I do not have any other three phase equipment. Maybe a lathe in the future but who knows.

However it is my understanding that VFD has some extra advantages like soft start over static converters, and no loss in power that is probably OK for my usage but... if I can avoid it...

You can use an inexpensive VF like the Teco L510, use it at a fixed 60Hz and continue to use the Vari-Speed head. The VFD would be directly connected to the motor and you switch the low voltage VFD inputs for the run commands.

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I followed until you said "you switch the low voltage VFD inputs for the run commands". Would you be so kind to explain a little better that part, as I am not 100% familiar with the terminology here.

If you had a larger motor on the head then a direct belt drive would be an option

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Out of curiosity, which motor would qualify there, how much power would it take for a direct drive to make sense?

With VFDs, the run controls are done by low voltage inputs and you program the VFD as to the action of each input. The VFD has a built in power supply, typically 12 or 24VDC that is specific for this purpose. You do not switch the motor output for stop/start or direction, the motor is directly wired to the VFD terminals. So to control the VFD you need to switch low voltage low current inputs, and you should not use the existing drum or rotary switch as these are designed for higher currents. They also develop contact resistance from arcing when they were used for motor switching. You can purchase inexpensive switch gear to do this. Also the controls can operate as 2 wire control which requires a sustained on command to run forward/reverse, or 3 wire control which uses momentary stop and separate momentary run switch and a sustained direction switch. If using 2 wire control, the mill will run when power up and the switch is in the F/R position, most VFDs have you can program to prevent this from occurring, i.e. the VFD motion will not execute with a run command on power up.

I like to put the run controls on the knee or a separate stalk closer to the user, the motor direction rotation and E-Stop was left on the head on some installs, others I also put it in the pod. In some installs I add other mill functions (see panel below), also sensors for back gear which keep the rotation of the spindle always the same (i.e. rotation is not reversed in back gear). This is easily done with VFDs.

On a manual mill of this size the typical minimum motor size would be in the 3-5 Hp range to run direct drive via a VFD, Ideally with 3 phase you would want what is known as an inverter/vector rated motor 4 pole which can spin up to 5000-6000 RPM. These motors typically maintain full torque down to ~0 RPM and full Hp above their base speed up to rated top speed (typically 3X the base speed). By operating the motor in the 60-180Hz range you are running at full Hp, torques does fall off, but you have a mechanical advantage (relative to the same speed with a 60Hz motor) which somewhat compensates for the torques decrease. Most high speed work is with small bits so loss of torque is less of an issue. My mill came with a factory 3 Hp inverter motor, I have never been able to see change RPM under load.

Also note that single phase inputs VFDs are relatively inexpensive and common up to 3 Hp, above this point the price goes up quickly because you typically need to purchase a 3 Phase input VFD and derate for use with single phase input. A general guidance is to double the size of the VFD for single phase input, so 10 Hp 3 phase input VFD run on single phase would be used for a 5 Hp motor. You might also get by with a 7.5 Hp VFD and use a DC choke to decrease the ripple. See link below which gives some details on derating for single phase input.
https://www.yaskawa.com/delegate/ge...D.15&cmd=documents&documentName=AN.AFD.15.pdf

manoweb said:

Hello I have brought home a Bridgeport 2HP milloing machine. I only have 240VAC single phase available.

It has a Varispeed head and it needs to be rebuilt as some of the components there are shot. Few hundreds of dollars for the parts, not a huge deal. However a VFD would allow me to change the speed of the motor too, even if it is considered detrimental to leave the Varispeed always in the same position as it would wear the assembly unevenly.

Any suggestions? I've read of people converting the Varispeed to a fixed pulley and use the VFD only. That would save a bit of money to pay for the VFD, but is it perhaps considered a hack job?

Any comment will be appreciated. I haven't used one of these machines in a good while, and most of my experience was on the lathe and the shaper anyway. Thank you

Click to expand...

I have a step pulley Bridgeport and use a 1 hp VFD that has a frequency adjust knob
Teco-Westinghouse, N3-201-CS-U, 1 HP, Variable Frequency Drive 230 Volt, 1 Phase Input, NEMA 1, at Dealers Industrial
I set the high end frequency to 65Hz and generally don't go lower than 45Hz although I could go the zero. I use the backgear if I want a slower speed.
VFD has a 8 second soft start
I had another Bridgeport that had the single pulley mod with VFD and worked fine
All stop/starts are done at the VFD using the soft keys. I didn't do any low voltage wiring.

OK thanks everybody for the advice. Now, I have decided to rebuild the Vari-Speed and to buy a VFD unit to deliver the 3phase. This way I have all the options open, both mechanical and electric.

Being a 80's 2HP motor, and of course I need a 230V, 1 phase input, what are some VFD models I should consider?

User mksj mentioned model L510 and I saw some online with 230V 1 phase input, 2HP or 3HP. The latter is about 30 bucks more than the 2HP, it sounds liek I should get that one:

L510-203-H1-U | Teco Westinghouse | AC Drives

Other units to consider?

mksj said:

You can purchase inexpensive switch gear to do this. Also the controls can operate as 2 wire control which requires a sustained on command to run forward/reverse, or 3 wire control which uses momentary stop and separate momentary run switch and a sustained direction switch. If using 2 wire control, the mill will run when power up and the switch is in the F/R position, most VFDs have you can program to prevent this from occurring, i.e. the VFD motion will not execute with a run command on power up. I like to put the run controls on the knee or a separate stalk closer to the user, the motor direction rotation and E-Stop was left on the head on some installs, others I also put it in the pod.

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But in a simpler situation - I can just use the buttons on the VFD unit itself right? I'd just like to start simple if possible and then adjust while I'm actually using the machine.

Also note that single phase inputs VFDs are relatively inexpensive and common up to 3 Hp, above this point the price goes up quickly because you typically need to purchase a 3 Phase input VFD and derate for use with single phase input.

https://www.yaskawa.com/delegate/ge...D.15&cmd=documents&documentName=AN.AFD.15.pdf

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Very nice document that one.

However, if I buy a VFD unit that is specifically 1 phase input, the nominal HP rating should be sufficient I believe, or maybe just a 50% more?

IWUP said:

I have a step pulley Bridgeport and use a 1 hp VFD that has a frequency adjust knob
All stop/starts are done at the VFD using the soft keys. I didn't do any low voltage wiring.

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I like that setup, I believe I want something very similar to that. However my motor is 2HP nominal so I need a bigger VFD unit...

manoweb said:

I like that setup, I believe I want something very similar to that. However my motor is 2HP nominal so I need a bigger VFD unit...

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Here's a 3hp version
Purchase 3 HP VFD, 230 Volts, NEMA 1/IP20, Teco, E510-203-H-U at Dealers Industrial
and a 2hp version
Purchase 2 HP VFD, 230 Volts, NEMA 1/IP20, Teco, E510-202-H-U at Dealers Industrial
Looks like the one I have was discontinued and replaced by these models

I would purchase a VFD from a US distributor, preferably a name brand type as opposed to the generic ones on eBay. Lots of reasons, but we do not need to go there.

You are not asking much of the VFD, basic single phase to 3 phase conversion and most of the speed adjustment will be mechanical. I would stick with something like 30-75 Hz as a reasonable speed range for this type of motor/age. Keep the carrier frequency at 8kHz or below in an older motor.

As far as size, if you only need 2 Hp, then just buy a 2 Hp VFD. The derating is only for 3 phase input VFDs not those that state single phase input. On the Teco L510, they are pretty bare bones, but they work OK in this setting. Reliability wise, I have not heard of any issues. Doesn't hurt to up size, might make a difference over many years of use. Typically the capacitors in the power supply have a finite lifetime (some VFDs have hour display for components), but there are many other contributing factors.

The Teco E510 is a better unit, but I haven't installed any of these, the E510 is more a replacement for the older Teco MA7200, N3. So more features, but maybe not needed. If you are not penny pinching then I would go with the E510-202-H-U, otherwise the L510-202-H3-U. I have had a few cases where the L510 didn't hookup well with the mill drive motor, also there was mention elsewhere that the drive is not a truly sensorless vector control which gives tighter motor control. Also the L510 (120/230V input models) do not accept an external braking resistor that is needed for quick deceleration times.

One thing I did notice with the E510 that may be attractive for your setup is the detachable keypad with speed pot that can be remotely mounted. You may just need to purchase a cable, that way you could mount that on the head of your mill with the VFD on the back of the mill away from swarf. Worth the price difference if you do not plan to run separate input controls.Comparative VFD models to the E510, but more expensive are Mitsubishi D700, , Danfoss VLT FC280, ABB ACS310, Yaskawa V1000, Hitachi WJ200 to name a few. I primarily use the WJ200 and V1000 VFDs, but much more complicates as to programming and features you do not need.

Thank you very much!

If you want to save some money and get running ASAP I have a static converter and also a larger 10hp? RPC that are surplus to my needs. Where in Ca are you?

The L510 has a sensorless vector setting. But not really?

I'm also new to VFDs. This is what little I've experienced and have learned mostly from this forum.

I bought an L510 because there's several youtube videos on setting them up, many more than any other model. I assumed this would make setup easier, and it did. It also implies they're popular with the home crowd, so I also assumed they're good units.

VFDs have an adjustable "carrier frequency" that is quite loud at lower settings. Lower settings are easier on the VFD, but harder on your ears and on the motor, especially older motors. I have mine on the highest setting because of this. Higher settings also de-rate the VFD. How much I'm not sure.

The L510 does not have an external brake resistor option. An external brake resistor stops the motor much faster than normal. I just checked and the E510 does have this option.

I sold my L510 and bought a Fuji Mini Frenic ($10-20 more expensive than the L510) and brake resistor, at the suggestion of Wolf Automation. It works well, but at least for me, it's much harder to setup, and there's little help to be had for it. Only the basics are covered on youtube and no one on this forum or any other seems to be familiar with them.

There's not much on youtube about the E510 either, but I imagine it's not all that different to program than the L510, so if had it all to do over again I think I'd opt for one.

ptsmith said:

The L510 has a sensorless vector setting. But not really?

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Sensorless vector implementation varies and how effectively it works. Not my background, but I have seen it mentioned several times, and at least twice specific to the L510.
https://www.practicalmachinist.com/...ions-312317/?highlight=L510+sensorless+vector

See the above thread, post #14. I also read something similar in another discussion by a experienced VFD engineer. I assume it all comes down to the hardware, computing power and programming; in this application probably a non-issue. As mentioned, I have had a few episodes where the L510 did not work well with a mill motor, and I tend not to recommend it for other applications which needs more functionality. It is a poor choice for a lathe, but acceptable for say a small grinder or bandsaw.

Derating for carrier frequency varies by VFD model/output rating, in this size VFD typically 8kHz and below there is no derating.

The E510 programming is similar to the L510, but a lot more programming options. One needs to spend some time reading the manual, and asking questions or have someone look over your parameter changes. Once you get into the programming, it becomes a bit more straight forward. You can always reset the VFD back to the default settings if you get into a bind. Using the keyad is pretty easy, although I typically use a laptop on the WJ200 and V1000 so I can track and tweak parameters during setup.

Just a FYI, the Teco's as well as a few other VFD manufactures can be confusing as to the input wiring for single phase input, input terminals are labeled as L1(L), L2 and L3(N). You do NOT connect the neutral wire to the VFD inputs, for single phase you connect 240VAC to terminals L1(L) and L3(N), ground to the ground terminal.

One last comment in favor of the E510 is that the VFD is a NEMA 4X rated, so much less susceptible to swarf and metallic particles getting into it, so it would be fine to use on a mill w/o a separate enclosure.

Rob F. said:

If you want to save some money and get running ASAP I have a static converter and also a larger 10hp? RPC that are surplus to my needs. Where in Ca are you?

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Thank you very much for the offer but I decided to go with a VFD. I need to rebuild my head anyway and it's going to take some time so I'm not in a rush. If I hear of anybody that needs something like this either among my neighbours or at work I'll make sure to direct them to this forum.

mksj said:

One last comment in favor of the E510 is that the VFD is a NEMA 4X rated, so much less susceptible to swarf and metallic particles getting into it, so it would be fine to use on a mill w/o a separate enclosure.

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Thank you very much, I am heading towards the E510 (probably in the 2HP size, as that is the motor I have); however I've found this article that specifically advices AC Tech Lenze for Bridgeport's:

Most recommended VFD for Bridgeport Mills | Wolf Automation

Any opinion on these before I place an order for the E510? Thank you!

The posting is from 2017, the L510 and E510 are more recent models. I looked into the Lenze years ago and went with other VFD's that were far more functional, OK but very dated VFD. They are more expensive, in particular the NEMA 4X versions. I think they were recommended because at the time is was sensorless vector and easy to setup, the programming on other VFDs was maybe more intimidating and the manuals were often marginal. The Teco's at the time was the FM50 which is a minimalist VFD,it is long gone, a step up was the 7200 and N3 series which did have sensorless vector. I recommend the E510 over the Lenze SMV, but I would speak with the people at Wolf Automation as to the Lenze SMV vs. the E510. At the end of the day it may not make any difference because you are basically using it for simple phase conversion. The E510 Nema 4X rating and remote keypad are no brainers for me in this application.

Again, thank you very much, I am very grateful for the advice.