Lathe power disconnect options

[William C Rogers]

I have the Laguna 18-36 lathe and the emergency stop switch is fixed in the headstock. I unplug the lathe every night and was thinking about putting some type of disconnect at the tailstock end to serve both to disconnect the power and use as an emergency stop at that end. What opinions do you have or what option are viable? Right now I would have to walk 25' to the breaker box to avoid crossing the line of fire.

i was even thinking of getting a 120/240 relay and one of the outdoor remote systems to do this.

[Prashun Patel]

LMK when you do it. I will copy

[Roger Chandler]

I was told by a turner that VFD's do not like a power disruption using a switch to just shut the power down. An emergency situation, where a blank is coming lose or such is not a regular happening, but just to power down the lathe is perhaps too frequently. Here is his quote to me in an email...


You mentioned adding a shop-made pendant for remote on/off control. I'd be interested in knowing more about the design of the one your club members demonstrated at show and tell. I considered adding one to my G0766 a year or so ago, but decided it would take more effort than I wanted to put into it right now. It's my understanding that, with these sensitive VFDs, you have to add the switching circuit to the actual VFD circuitry at the headstock, not just put it between the 220v receptacle and the lathe's power cord. Switching the 220v power off and on to the inverter while the lathe is operating is supposedly not good for it.



Now for my part, I do not really know for sure, but I think this gentleman likely knows what he is talking about, so I am going to not put a power interruptor between the headstock and outlet because of this. Wired into the headstock circuitry might be the way to go, and not just a switch to kill the power for everyday use.

[George Troy Hurlburt]

To each his own, but I have 4 lathes on computers, I don't ever disconnect. I have seen sparks fly out of the plug-ins box. I have wood dust in the air and maybe even finish fumes. Having arthritis doesn't help any. It's been this way for almost twenty years. Once I plug a machine in that's it, unless I have to move it. Don't you think all the other plug-ins in your house is similar. Like computers, stove, washer, dryer, water heater, microwave, dishwasher, TV, stero,golf cart,etc.and electric furnace.

[David Delo]

LMK when you do it. I will copy

I did PM you back on that other matter, did you get it?

[William C Rogers]

Hmm! So far what I have been doing is pushing the emergency stop and then unplugging the machine. I am somewhat remote and we see power disruptions about 4 times a year, so don't want a surge to fry my VFD. So I would push the emergency switch and then kill the power to the lathe. Is it wrong to use the emergency stop this frequently?

[John Keeton]

To each his own, but I have 4 lathes on computers, I don't ever disconnect... Don't you think all the other plug-ins in your house is similar. Like computers, stove, washer, dryer, water heater, microwave, dishwasher, TV, stero,golf cart,etc.and electric furnace.

Aside from the electrical considerations, there is one other possible consideration. If you produce any revenue from your turnings, it is likely your lathe is not insured on your homeowners policy, whereas the household appliances are. My homeowners would not cover my shop building nor the contents without the commercial rider I have.

[Roger Chandler]

Hmm! So far what I have been doing is pushing the emergency stop and then unplugging the machine. I am somewhat remote and we see power disruptions about 4 times a year, so don't want a surge to fry my VFD. So I would push the emergency switch and then kill the power to the lathe. Is it wrong to use the emergency stop this frequently?

The emergency stop is wired into the lathe circuitry, so the vfd accounts for it. If I understand correctly, it is just abruptly cutting power by means of wiring not run through the circuitry which has the vfd in the sequence. I have not investigated this personally, but am not willing to chance creating vfd problems, until somone like an electrical engineer [Sparky or Bill perhaps] can speak definitively to this.

It does seem to me, that a switch added to the power cord would be in sequence since the lathe cord is in sequence with the vfd wiring, though.......hummmm? Perhaps, it could be that the extra switch bypasses the emergency stop button that is in sequence with the vfd?

[William C Rogers]

The emergency stop is wired into the lathe circuitry, so the vfd accounts for it. If I understand correctly, it is just abruptly cutting power by means of wiring not run through the circuitry which has the vfd in the sequence. I have not investigated this personally, but am not willing to chance creating vfd problems, until somone like an electrical engineer [Sparky or Bill perhaps] can speak definitively to this.

It does seem to me, that a switch added to the power cord would be in sequence since the lathe cord is in sequence with the vfd wiring, though.......hummmm? Perhaps, it could be that the extra switch bypasses the emergency stop button that is in sequence with the vfd?

So now I'm totally confused! How should one power down the lathe and VFD. The emergency stop kills the power to the motor and display, but the VFD is still powered. Forgetting about the emergency stop, are we saying unplugging and replugging the lathe is a problem? Isn't that the same as putting a disconnect in line with the power?

what is recommended?

[Roger Chandler]

So now I'm totally confused! How should one power down the lathe and VFD. The emergency stop kills the power to the motor and display, but the VFD is still powered. Forgetting about the emergency stop, are we saying unplugging and replugging the lathe is a problem? Isn't that the same as putting a disconnect in line with the power?

what is recommended?

I would not think so, because that is the way it is designed.....the stop button works in sequence with the vfd and other circuitry. If one has an extra switch, and shut off occurs by bypassing the circuitry, could that not allow for power surge, or simply gets the sequence off cycle? Again William, I am NOT AN EXPERT in electronics, but know enough that VFD's are sensitive equipment. That quote in blue from another turner gave me pause, as I was planning to put an extra shut off switch on my power cord by using an extension cord wired into a switch [appropriately sized wire of course]

I am wondering out loud, and you should seek more qualified advice than I can provide..........this quote came to my mind when I saw your question. I just know that until I could find out definitively from experts, that I would not do it personally and risk vfd damage. It may be that it won't damage the vfd, and I hope one of our creekers who is an electrical engineer can speak to this. You would be safe I think just uplugging the lathe.

[John Keeton]

The attached files are excerpts from the manual for the Revo 2436, which does have the remote switch. They are Greek to me, but perhaps one of you electrically gifted folks can find the answer from these.

[William C Rogers]

I would not think so, because that is the way it is designed.....the stop button works in sequence with the vfd and other circuitry. If one has an extra switch, and shut off occurs by bypassing the circuitry, could that not allow for power surge, or simply gets the sequence off cycle? Again William, I am NOT AN EXPERT in electronics, but know enough that VFD's are sensitive equipment. That quote in blue from another turner gave me pause, as I was planning to put an extra shut off switch on my power cord by using an extension cord wired into a switch [appropriately sized wire of course]

I am wondering out loud, and you should seek more qualified advice than I can provide..........this quote came to my mind when I saw your question. I just know that until I could find out definitively from experts, that I would not do it personally and risk vfd damage. It may be that it won't damage the vfd, and I hope one of our creekers who is an electrical engineer can speak to this. You would be safe I think just uplugging the lathe.

I understand what you are saying Roger. I just don't know about these things and hope someone can comment. I thinking two things. One is removing power via of a switch when the lathe is running (emergency) be pulling the plug and two removing power when the lathe is not running (pulling the plug). So maybe the emergency stop has circuitry to prevent damage to the VFD when the lathe is running. Like John I don't understand. I will call Laguna tomorrow to see what they say. I do remember they told me to unplug the lathe when not in use to prevent damage from power surges.

[John K Jordan]

I have the Laguna 18-36 lathe and the emergency stop switch is fixed in the headstock. I unplug the lathe every night and was thinking about putting some type of disconnect at the tailstock end to serve both to disconnect the power and use as an emergency stop at that end. What opinions do you have or what option are viable? Right now I would have to walk 25' to the breaker box to avoid crossing the line of fire.
i was even thinking of getting a 120/240 relay and one of the outdoor remote systems to do this.

I have an emergency stop switch on my PM3520b which is tied into the low voltage control circuit for the VFD, just like the main stop switch on the front of the lathe. This stops the lathe but doesn't kill the AC power. Killing the AC power results in delay when powered up again while the VFD boots up or something.

I do disconnect my lathes from the power when I leave the shop to minimize possible damage from power surges. (I had a VFD fail on a lathe that I kept plugged in all the time but I don't know if it was due to a power surge.) For the PM I use a double-pole switch mounted in a metal box stuck to the end of the end of the lathe with magnets. For another lathe, a Jet1642, I disconnect with a 110v power strip which also controls the lights over the lathe.

BTW, I do not like to disconnect things by unplugging or by turning off a breaker because receptacles and breakers are not designed for that. A relay would work nicely but would be complicated compared to a switch. To be complete, I read that a surge from lightning could come in on the ground wire too. However lightening can jump across the room so I'm not sure how you could perfectly protect from lightning without working under ground.

JKJ

[Glenn C Roberts]

Just put the tail stock shut off in series with the headstock shut off. Easy.

[Brice Rogers]

On the G0766, if you are running the lathe and hit the emergency switch, it will somewhat slowly coast to a stop. If I pull the AC plug, exactly the same will happen. If I rotate the speed control to zero it will slow down faster. The "reverse EMF (electro-motive force) apparently is dissipated in the output semiconductors. If I had installed the braking resistor, this power would have been dissipated in them.

Interestingly, the main power on switch has a latching relay in it. So, when it is off, there is no electrical voltage to anything other than the switch. When I press the main power-on switch, then it "latches" and applies power to the VFD, etc. So, when the main power is off, the lathe is somewhat isolated from the mains. BUT, if, say a 10,000 volt surge comes into the lathe, it may (or may not) jump past the main power-on/off switch. What do I do if there is an electrical storm coming in or I'm going out of town? I unplug the lathe. If I get hit by lightening, it is unlikely that the "jolt" will jump several feet. A quarter inch? Yeah, maybe.