Tablesaw On/Off Switch with VFD

[fRED mCnEILL]

For those of you who use a VFD on their tablesaw I would be interested in knowing how you turn you saw on/off.
I personally have a rotary phase converter and have a magnetic switch on the saw outfitted with a "paddle" that lets me shut the saw off with my knee or foot. However I understand you can't use a switch in between the VFD and the saw.

On tools like drill presses, lathes etc an emergency shutoff may not be as critical as a tablesaw so am wondering how others do it.

Thanks

Fred

[Van Huskey]

Most if not all VFDs will have low voltage muti-function pins that allow for you to use a standard on-off switch or a forward/off/reverse switch. They for example can also be wired through a microswitch for a foot brake on a bandsaw and I have my jointer wired through the brake as well so I push the brake for my jointer and it cuts power to the motor which it was also designed to do without a VFD. VFDs are extremely flexible.

[Rich Riddle]

I never place a switch between the vfd and the motor; however, you can wire the switch to the low voltage side of the vfd. You are then using the same switch on the machine but cutting power/initiating power at the vfd itself.

[fRED mCnEILL]

Anyone else?

[Van Huskey]

Anyone else?

Not sure you are going to get much else unless you are interested in specific setups or part numbers for specific switches.

There are basically three ways to turn a machine off using a VFD.

1. use a high voltage switch to cut power to the VFD which is not ideal and you lose any braking you have set up in the VFD

2. use the switch on the VFD itself fine for some machines but as you mention you do not have a "quick slap" switch

3. use the low voltage circuit on the VFD to add an auxiliary switch that suits you where you want it which is anticipated and provided for by the VFD's design. This also allows you to use the braking potential of the VFD to stop the machine faster than it would ordinarily. If you use braking you do have to be careful not to use too much braking on something like a table saw since it can loosen the arbor nut so it is not as much safety on a TS just more a couple of extra seconds you save before you can move the wood.

[Mike Hermann]

Your power cord supplying single phase power (often 230V) goes straight to the VFD, and the VFD is wired straight to the 3 phase motor (making sure your motor is also wired for 230V). The VFD will often have teeny little start/stop buttons on them that will operate whatever equipment you have wired in, but reaching and finding those buttons is tough especially if you're in a bind. There are a number of terminals on a VFD that allow you to wire in a number of external controls, commonly a start/stop switch and a potentiometer to control motor speed.

The start/stop has to be something like a paddle switch, toggle switch, heck even a light switch, anything that will make a circuit. It only needs to be something that can carry a low voltage signal. Magnetic switches/starters will not work here though. I just use a fairly standard red-and-yellow paddle switch because they are easy to operate, and on my table saws, I can just bump them with my thigh to turn them off. The wire to these switches can be light gauge (I use lamp cord from a spool I acquired), but can be whatever you have on hand as long as it fits in the VFD terminals. Remember though: nothing, and I mean nothing, goes between the VFD and the motor.

I'm not an expert, but I have three VFD's on different machines, and this is what I learned. Each one has been easy to set up, and I'm able to customize the settings on each machine based on my needs. I can program in a soft start, add a little bit of braking when I shut a machine off, and vary speed if needed. On my lathe, I added a potentiometer to control speed and a FWD/REV switch so that I can sand my turnings in both directions. As Mr. Husky says above, VFD's are flexible.

--Mike

[Matt Day]

Fred,
Try asking over at OWWM, there is a lot of VFD usage there since many old industrial machines are 3 phase.
I'd be interested too since I need to decide what I'll do with my Unisaw. On the PM65 I restored I put in a mushroom push button (see below) on it and it worked good. On this one I may try a bigger paddle style (likely Shop made) that I can use my knee on. We'll see.
https://www.amazon.com/gp/aw/d/B008L...w4L&ref=plSrch

[mreza Salav]

Van gave you the easy solution. Here is how I've setup my bandsaw:

http://www.sawmillcreek.org/showthre...VFD&highlight=

The switch is an off-the-shelf one and can be placed anywhere you like or you can install a bigger paddle switch if you like.
It is wired to the control lines of the VFD and it is wired such that in case of a power failure your saw won't run (if the switch is left in "On" position) until you turn it off and then on again.

[Rich Riddle]

Matt,

You will get the same three answers on OWWM that Van outlined. I spent New Year's day at Bruce Norton's house in Tennessee discussing this. He's the guru (and an engineer) in OWWM for VFD applications. You can do it a few other ways that aren't recommended but you chance damaging equipment. The wiring of a VFD is fairly straight forward....the programming isn't as simple.

[fRED mCnEILL]

Thanks for the replies.

What is OWWM?

Regards

Fred

[Matt Mattingley]

Old Wood Working Machinery.com . But if you have any more concerns, I will try to answer as many as possible.

[fRED mCnEILL]

Thanks Matt.
I think I have enough info for now. What I thought might be a deal breaker for a VFD( i.e. on/off switch) turns out to be quite simple once you understand all the capabilities of a VFD.
I will keep you in mind if/when I have trouble with the install.

Regards

Fred.

[Terry Therneau]

There are two ways to wire start/stop on a VFD. The simple one is just like a light switch. For instance I have a VFD on my dust collector(a craigslist find with a 5HP 3phase motor), and I have multiple on/off switches in the shop that are wired exactly the same way you wire multiple switches for a light bulb. I can turn it on or off from anywhere. Except of course that the wire is a leftover spool of telephone wire that I happened to have. I have another on a table saw using a large mushroom switch such as Matt showed, in a spot that's easy to slap without looking.

The second way uses a pair of momentary push buttons, one normally closed and the other normally open: the usual "start/stop" pair you see on lots of machines. This setup is a bit safer in that if power were to go out (or a breaker trip), the saw won't start back on when the power is restored. Those switches are a bit more expensive since they usually come from the industrial side of the electric catalog rather than a big box store. I also have this style.

Every VFD I've seen allows either style, you just need to read the manual and set it up. For something like a saw or shaper my main criterion is a BIG stop button.

Terry T.

[Matt Mattingley]

Some better VFD's have eight inputs or more.
you can set:
input #1 to be the stop
input #2 to be forward running
input #3 to be reverse running
input #4-8... pick whatever you want that fills your needs.
And about 100 different commands including different speeds, breaking speed's, Potentiometers, command switch overs, counters, jog options, ... The list is pretty unlimited.

As Terry stated there is Basic two wire control, Basic three wire control (these are momentary pushbuttons) and then you can get into basic four wire control which has reverse. Some of the better VFD's are not just phase conversion. They are in miniaturized switching station/computer.

[Tom Trees]

Anyone else?

Hi Fred Delighted this threads up here as I'm looking for a similar solution http://www.sawmillcreek.org/images/smilies/smile.gif Here's what I've done for my bandsaw ... I sometimes get fatigued all of a sudden sometimes , so I wired up two stops (3 wire control ) using a N/O start switch and 2 N/C stop switches in series . These buttons need to be twisted to activate the saw once pressed . Although if i trip the saw out ....It happened once or twice using the pot, when I was fettling/testing my BS tires, I had to press the stop button on the VFD to get it going again (Huanyang drive) It did not start again on its own ... Now onto the tablesaw I don't think these stop switches are exactly what I'm looking for with this application as there not large enough for my liking ... I was considering making some kind of paddle type device that Kelly Mehler uses masteringyourtablesaw 1 but I think I like a horizontal type paddle better like Carl Holmgren's on youtube He uses a toggle type switch in which you have to lift the horizontal beam up to activate the saw and hit it down to stop it . I might use this in conjunction with an awkard twist isolator switch, for any eejits If I ever had a party of folks come over ... although I think I will just remove the fuses instead if that ever happens . I could just make some kind of a hidden hook for the paddle aswell ...this might prove to be a better solution Awaiting some piccys if anyone has a better solution . Thanks Tom