VFD for 10k - Pros and Cons of using the stock Forward/Reverse Switch

datmony · Apr 27, 2016

I just finished the rebuild of my 10k last weekend and my VFD just showed up yesterday, a Teco, N3-203-CS-U. For those of you who have set your lathes up with VFD, what are the pros and cons of wiring the stock switch into things?

It seems like it would be a simpler installation to simply just wire the motor to the VFD and wire the VFD to the single phase power and just skip the manual forward/reverse switch on the lathe and use the forward reverse functions off of the VFD instead. Am I missing something there?

For those of you that did wire in the switch.... what made you do that? Is there some benefit of having it run through the physical switch versus the VFD itself that I am missing?

Thanks in advance!!

Ziggy2 · Apr 27, 2016

The issue is that the VFD does not like to see the motor lines go open while in operation. This causes the creation of an over voltage condition at the IGBT that can be destructive. Using the drum switch for reversing makes the situation even worse.

What you can do is use the drum switch for your ON/OFF FWD/REV switch and just run the low voltage signals to the VFD terminal strip. This makes the VFD happy and everything will still function the way you want it.

iwananew10K · Apr 27, 2016

What motor are you using with it? That's a pretty substantial drive for a 10k.

jmm03 · Apr 27, 2016

Dat, there is no problem using the existing forward/reverse switch to control those functions of the VFD as long as you only switch the low voltage inputs. You will remove all wiring going to the line and load side of the existing motor and then you can run a shielded 3 wire cable, (or three separate wires) from the appropriate terminals on the VFD back to the switch. One wire will be the common "hot" and the other two will be the forward and reverse inputs. You may need to modify the contacts on the switch to isolate them in the switch, at least I had to when I wired up my buddies Clausing. You will also need to adjust your VFD parameters. (hope this isn't too redundant, I am a slow typist and Ziggy sortof already gave you the same info...) Jim

datmony · Apr 27, 2016

It is just the original 1/2 HP motor. I just bought a larger VFD because it might get used on one of my mills at a later point that could have a 2-3HP motor.

datmony · Apr 27, 2016

jmm03 said:
Dat, there is no problem using the existing forward/reverse switch to control those functions of the VFD as long as you only switch the low voltage inputs. You will remove all wiring going to the line and load side of the existing motor and then you can run a shielded 3 wire cable, (or three separate wires) from the appropriate terminals on the VFD back to the switch. One wire will be the common "hot" and the other two will be the forward and reverse inputs. You may need to modify the contacts on the switch to isolate them in the switch, at least I had to when I wired up my buddies Clausing. You will also need to adjust your VFD parameters. (hope this isn't too redundant, I am a slow typist and Ziggy sortof already gave you the same info...) Jim

I think perhaps the main focus of my question might have been missed based on the responses. My question is more.... can I just skip the stock switch altogether and ONLY use the VFD? I believe that is answer is yes and can't see why I wouldn't go tat route for simplicity but was trying to figure out why folks are adding the complexity of also using the stock switch and what benefits its benefits would be.

WJ Birmingham · Apr 27, 2016

datmony said:
I think perhaps the main focus of my question might have been missed based on the responses. My question is more.... can I just skip the stock switch altogether and ONLY use the VFD? I believe that is answer is yes and can't see why I wouldn't go tat route for simplicity but was trying to figure out why folks are adding the complexity of also using the stock switch and what benefits its benefits would be.

Yes! You can skip the switch altogether and use the VFD faceplate controls, or external controls wired through the VFD low voltage side.

Dobermann · Apr 27, 2016

Yes, you can use VFD functions to control fwd/rev of the drive motor. HOWEVER if you've become used to using the usual drum switch to control those functions and you're already used to where control is, it seems to me you'd be much better off to continue to use that switch to control the motor. Besides, given the low voltage and infinitesimal current you'll be switching, the "old" drum switch should well into the next century.

CarbideBob · Apr 27, 2016

datmony said:
.... and can't see why I wouldn't go tat route for simplicity but was trying to figure out why folks are adding the complexity of also using the stock switch and what benefits its benefits would be.

Maybe some do it for the same reason I put remote pushbuttons and speed adjust on any VFD.
Ease of use as the VFD is usually shielded from chips and gunk. Along with that those membrane keypads give up the ghost with often use.
For sure you can do it all on the keypad but it is not so handy.
What seems like no big deal at build sometimes becomes a pain in the butt down the road. You get tried of it eventually.
The real genius of the bridgeport mill is that you can do everything without moving one step and without thinking.
Sooo.... It's a user friendly thing.
Bob

datmony · Apr 27, 2016

Makes sense, so main reason to use the stock switch is to not have to change a behavior. For the short term, since this is the first lathe I have ever owned, I will likely just use the VFD for everything and then decide if I want to add the switch back in the mix. I don't have any behaviors I would have to break myself of since I don't have any "muscle memory" established.

datmony · Apr 27, 2016

CarbideBob said:
Maybe some do it for the same reason I put remote pushbuttons and speed adjust on any VFD.
Ease of use as the VFD is usually shielded from chips and gunk. Along with that those membrane keypads give up the ghost with often use.
For sure you can do it all on the keypad but it is not so handy.
What seems like no big deal at build sometimes becomes a pain in the butt down the road. You get tried of it eventually.
The real genius of the bridgeport mill is that you can do everything without moving one step and without thinking.
Sooo.... It's a user friendly thing.
Bob

That makes total sense. For me right now it is a get this thing up and running. After that is accomplished and I have been able to learn a bit, then I will look to optimize controls.

WJ Birmingham · Apr 27, 2016

For my auto-driven reloading presses, I use the AutomationDirect.com stuff. The switches are reasonably priced, along with the enclosures. They also have potentiometers available.

http://www.automationdirect.com/adc...tons_-z-_Switches_-z-_Indicators/22mm_Plastic

I will eventually get around to using one of their GS2 VFDs for my lathe.

TheOldCar · Apr 27, 2016

I used my original switch on the SB 13 when I connected my VFD. Mainly because I liked the way the original switch looks!

steve-l · Apr 28, 2016

I'm confused. Are you installing a single phase VFD? If so, it sounds rather pointless. The 10k is a light lathe, so it moves around and flexes a bit. You may notice that when trying to generate a very fine finish with a single phase motor in high gear there will be a very fine herringbone pattern on the work surface. This is due to the torque impulses from the single phase motor (velocity modulation). This completely disappears when using a 3 phase motor, as its rotation is much smoother. Secondly, the lathe drive will slip when trying to use anything greater than 1 hp motors, don't install larger motors.

jim rozen · Apr 28, 2016

"main reason to use the stock switch is to not have to change a behavior..."

Well that's not going to work. You'll *have* to change behavior as there is an extra
control to work. The speed knob.

So if you want to retain the drum switch then figure out where the speed knob
is going to go and how it's going to integrate in terms of operation. One reason to
avoid keeping the drum switch is if you are used to plug reversing the motor, which is
to say going from fwd to reverse to stop the spindle - if you had factory three phase or
rotary converter three phase before installing the VFD.

The options are, integrate the drum switch into the control circuit for the VFD and mount
a small box near that for the speed pot. Or, figure a way to install the speed pot right
*in* the drum switch housing, possibly by gutting a portion of the switch out. Or, eliminate
the drum switch and simply replace it with a center off toggle and the speed pot in a tiny
enclosure, mounted in the same location.

I'll be going though this exercise soon myself as I'm going to bring up a new (well new to me)
heavy 9 lathe with a VFD as soon as I can dig up a one hp three phase motor.

gadget73 · Apr 28, 2016

Whatever you do with the controls, make sure you place them where they are accessible without having to lean over any spinning bits or move away from the lathe.

Personally I'm not real big on using small switches for equipment controls. In most good pro installs, the switch operators are substantial and spaced far enough apart that you won't hit multiple things at once. They also usually require enough effort to operate that you aren't liable to overshoot or accidentally turn something on. I tend to like the Allen-Bradley stuff, but that might just be because its what I deal with at work. We have some Telemechanique and Seimens stuff in places, and usually it seems that whenever we need a something for them, the series is discontinued and the whole works needs changing. The A-B stuff is pricey but our mid 1980s vintage controls are still supported without any problem.

Tony Quiring · Apr 28, 2016

BTDT!

okay splaining...

Open drum switch and remove all wires.

You should have 3 rows of switch parts that form a make break make arrangement.

You need 3 commands.

Run
Reverse
Stop

Simple.

For run you make top one close the run logic from VFD in either direction so connect outside terminals together and connect run pair to one and center so it connects on either direction.

For reverse connect reverse logic to next set to connect towards reverse

Now modify the contacts on the last row so they make before the others.

A little bending is all that is needed and not much either.

Connect same as run.

How it works.

After bending stop makes contact then run makes and it goes.

Same for reverse.

When you turn through center stop opens up to stop.

We posted same for our SB14.5 a couple years ago.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

datmony · Apr 28, 2016

steve-l said:
I'm confused. Are you installing a single phase VFD? If so, it sounds rather pointless. The 10k is a light lathe, so it moves around and flexes a bit. You may notice that when trying to generate a very fine finish with a single phase motor in high gear there will be a very fine herringbone pattern on the work surface. This is due to the torque impulses from the single phase motor (velocity modulation). This completely disappears when using a 3 phase motor, as its rotation is much smoother. Secondly, the lathe drive will slip when trying to use anything greater than 1 hp motors, don't install larger motors.

Motor is a 1/2hp 3 phase. VFD is a single phase 230 to 3 phase 230. Planning to use the existing motor. The only reason I bought the larger VFD was for future flexibility of using that VFD on one of the mills if I swap them over to 3 phase motors.

datmony · Apr 28, 2016

And thank you to everyone for all the thoughts. I actually have never ran this lathe. I got it from a demolition company that had removed it from a technical college. The main reason I was trying to go for simplicity in the initial install here was that I had actually never had a way to test the motor and for all I knew it was totally fried. Someone had crunched a LOT of gears on this thing and I replaced a boat load of them as I did the rebuild and I am betting this thing was sitting for many many years prior to the demo company getting to it and further damaging it.

Thankfully however, I hooked it up to the VFD last night and the motor still works. I will be setting up some sort of larger remote controls for it but frankly I don't know what I want yet so that will involve a lot more reading, you tube videos, and in general just getting accustomed to the machine first. That may involve the drum switch or may not.... frankly haven't decided yet. I am impressed by the flexibility of the VFDs though and that you can pipe in external controls to them.

Hopefully the new belt should be here tomorrow and I took the day off to do the last few things to get it all up and going. At some later point I will buy some stuff for the additional controls and figure out a good lay out for those but for now I am just anxious to see the chuck spin since I am betting it will be the first time in decades.......

ronlyke · Apr 28, 2016

I bypassed the switch when I installed a VFD on my 10L. I think I read somewhere (it may have been on the internet, so it must be true) that you should not have another switch. Don't know why.

VFD for 10k - Pros and Cons of using the stock Forward/Reverse Switch

Aluminum

Stainless

Diamond

Hot Rolled

Aluminum

Aluminum

Cast Iron

Hot Rolled

Diamond

Aluminum

Aluminum

Cast Iron

Attachments

Stainless

Titanium

Diamond

Hot Rolled

Titanium

Aluminum

Aluminum

Cast Iron

Similar threads