# 3 Phase Emergency Stop Switch



## Canus (Feb 10, 2021)

Is there such a thing as an Emergency Stop Switch for a 3 phase device?  I have a Southbend 16" lathe and would like to install an E stop switch on it.  I would assume it would be a NC switch that will open when pressed.


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## sdelivery (Feb 10, 2021)

It will have to run through the motor contactor coil circuit, simply place it in series with the coil circuit.


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## nnam (Feb 10, 2021)

Yes NC switch.



			https://www.diychatroom.com/attachments/wiringdiagram1c-jpg.27178/


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## nnam (Feb 10, 2021)

The general idea is to use a physical temporary button to get power to a NO switch.   Once it's closed by the temporary power, it powers itself,  and the 3 phase contactor.   Then a momentary switch to open a NC to cut power to the NO switch to shut everything down.


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## Bi11Hudson (Feb 10, 2021)

Such an animal as you are looking for does indeed exist. Actually several makes. You need to look into purely *industrial* devices. There are also single pole devices that will shut off the coil to the "M" contactor or the entire control system. They are much more reasonable in cost but not so absolute in power interruption. You just need to look outside the "hobby" circle, and *forget electronics*. You need an *electrical* control device.

.


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## Ulma Doctor (Feb 10, 2021)

to effectively cut off the power, you may need a 3 pole e-stop, unless you were to break the power with a control circuit


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## Canus (Feb 11, 2021)

There is no control circuit.  Lathe is wired directly into 3 phase power.  Looking for a switch like Bi11Hudson and Ulma Doctor refer to.  Google search has failed me so far.  Anyone have a link to such a switch?


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## sdelivery (Feb 11, 2021)

What does your electrics look like?
I couldn't get a good pic of my 16 x 72 s.b
Electrics.
I dont really understand why you want a e stop switch as it is not going to stop motion, this machine will coast to a stop and if the feed is engaged it won't stop the feed until the rotation comes to a complete stop and if you are going to use a VFD you sure dont want to open the output legs while it is running so that being said you could use a the drive to decrease stopping time of the drive motor.
With the correct drive and dynamic braking system you could make the spindle come to a stop quickly but the circuits need to be designed with the complete picture in mind not just a pretty red button that does nothing more than the existing on off circuit.

You SHOULD have a motor starter with thermal overload if you are NOT running a VFD.
We can make many recommendations but without completely understanding how you are going to power this (3 phase, vfd) and what your end goal is it will all just be confusing as each poster leads you down a different path.


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## Canus (Feb 11, 2021)

Current setup is as follows:  3 phase input power, from RPC, to rotary switch, from rotary switch to motor.  Not aware of a motor starter or thermal overload unless they are built into the motor.  Am aware that killing power will not immediately stop the motor.  Just want a way to kill power in the event of an emergency without having to activate the rotary switch.  Have located the following switch but not sure if it will do what I want. 
ES-P-230002​


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## nnam (Feb 11, 2021)

You can try:




			momentary start stop switch - Google Search
		


and a 3 phase relay contractor 



			240v 3phase relay contactor - Google Search
		


and check wiring :


Middle is the contactor 
Bottom is the overload relay


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## sdelivery (Feb 11, 2021)

Great drawing nnam.
I see you copied it but it is still a great drawing.


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## Canus (Feb 11, 2021)

I am aware of how a contactor works and, although an expensive and complex system, this would work however I would prefer a simple 3 pole e stop switch if one exists.  KISS


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## nnam (Feb 11, 2021)

Can you use the top item, circuit breaker only for your  need?  There are other variations without the fuse/breaker, which is basically 3 phase switch, you would pull down and up a handle to turn on or off.  Unless you want a touch to shutdown button style, which is like a toggle.  3 phase is a heavy duty and it's hard to have a light touch cut off.  High voltage is also a danger.  There may not be a simple solution and cheap for this.  Unless you can find a used set up somewhere people don't use anymore and throw away.  I keep a pile of them.


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## Canus (Feb 12, 2021)

I'm looking at a ES-P-230002 E stop switch.  Would appreciate it if someone with more electrical knowledge than me would review the attached file and let me know if this switch will work for my application,


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## ttabbal (Feb 12, 2021)

The part that would make me think perhaps that isn't a good choice is the "Operational Rating" of 3A. Most 3 phase machines would use more than that. You would need one that could handle the full current level the machine will draw if you are not using a contactor or similar. The smallest I would use is the amperage level on the motor nameplate. Anything less risks various failure modes that could well result in the e-stop failing to stop the motor. Which in my mind would be worse than not having one at all. If it were me, I would likely want a large safety margin as well, 2x or so. Sadly, that is not going to be cheap.


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## Canus (Feb 12, 2021)

Thanks ttabbal that is the information I needed.  Guess I'll have to go with a contactor after all.  Now to find a NC contactor.


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## Papa Charlie (Feb 12, 2021)

If you go with an industrial type of switch, you buy the actuator and then buy the contactor block that screws to the back of the actuator body. 

Here is one type you can buy through McMaster Carr. There are other designs that use the same principle. Just do a search in MC for 22 or 30 mm push button switches.









						McMaster-Carr
					

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




					www.mcmaster.com


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## mksj (Feb 12, 2021)

The issue with most E-Stop switches is that they cannot handle the current load of the motor which I assume is 2-3 Hp and you usually do not want 3 phase power/current switched at the front panel/machine. Typically, as others have noted, is to switch the contractor coil.  You can buy an integrated contactor/thermal overload with E-Stop in an enclosure that could be mounted on the side or somewhere near the front. Having a thermal overload for the motor is probably a good idea. You would need to specify the voltage and the amperage of your motor.









						Enclosed Start Stop, E Stop Motor Starter Compressor Saw Grinder 0.5Hp to 12HP  | eBay
					

12 HP.  3 Phase 575V. 12 HP.  3 Phase 440V. 10 HP.  3 Phase 380V. 5.5 HP.  3 Phase 220V. 3 HP.  1 Phase 220V. 1 HP.  1 Phase 120V. Select Cover :E Stop Button or Start Stop Pushbutton. The Starter is Suitable for Three Phase and Single Phase Motors.



					www.ebay.com


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## tq60 (Feb 13, 2021)

As others stated, you need a motor starter.

It s a REQUIEMENT !

your motor has zero protection so overload cantoast the motor.

The starter should allow "remote control" so simple off the shelf panel switches solve that.

Many already built surplus items on ebay.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## Bi11Hudson (Feb 13, 2021)

My understanding of VFDs is that there should be no switches between the VFD and the motor. Dual speed switch excepted. Reversing is done through the VFD. However, the VFD should have an "E-Stop" function available that can be remoted. Two wires and a NC latching pushbutton should do the job. Worst case is to interrupt line power to the VFD.

.


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## Canus (Feb 13, 2021)

I really appreciate all input received so far but it seems I need to clarify my situation.  I have a 1953 Southbend 16" lathe that I am powering with a home built RPC.  I have been using this lathe for over 5 years and it has functioned fine as is.  Since I usually work in my shop alone I simply want a way to be able to shut it down should I ever get tangled up in the chuck or a rotating workpiece.  I realize just killing the power to the motor won't stop the lathe instantly but at least with some sort of kill switch I would be able to kill the power and hopefully allow me to extricate myself.  Not being an electrician I don't understand why I would need a "motor starter" or even what a motor starter is or does.  If I have to install a contactor to be able to kill power to the lathe I will do so.  Again I really appreciate all input received but am looking for a simple solution to a simple situation.


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## sdelivery (Feb 13, 2021)

You can pay a contactor big bucks to build what nnam posted earlier or you can build it yourself.
There is a reason for each of the components and not only is it industry standard for decades but what is required by code in many areas.
You can buy the components new or used....here is an example from HGR.
I dont believe it is correctly sized but is a good example of what is available used.


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## Todd727 (Feb 13, 2021)

Canus said:


> I really appreciate all input received so far but it seems I need to clarify my situation.  I have a 1953 Southbend 16" lathe that I am powering with a home built RPC.  I have been using this lathe for over 5 years and it has functioned fine as is.  Since I usually work in my shop alone I simply want a way to be able to shut it down should I ever get tangled up in the chuck or a rotating workpiece.  I realize just killing the power to the motor won't stop the lathe instantly but at least with some sort of kill switch I would be able to kill the power and hopefully allow me to extricate myself.  Not being an electrician I don't understand why I would need a "motor starter" or even what a motor starter is or does.  If I have to install a contactor to be able to kill power to the lathe I will do so.  Again I really appreciate all input received but am looking for a simple solution to a simple situation.


Knowing this, I’d suggest you replace the RPC with a VFD. It will be so much easier to do what you want plus add some more functionality. I use a VFD on my SB.  I’ll shoot you some pictures of the control box I have for it.


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## Papa Charlie (Feb 13, 2021)

What kind of protection do you have between the RPC and lathe?

Are you using a switch of any type between the two other than the rotary that you mentioned?


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## Bi11Hudson (Feb 13, 2021)

My apologies Sir, I thought I read that you were using a VFD. An RPC, while accomplishing the same end result, is a "whole different ball game" in how that end result is accomplished. For a "non-electrical" person, I offer:


			http://www.hudsontelcom.com/uploads/ShopElex.pdf
		

a treatise on the subject. Motors, specifically, are not covered far, it's just an introduction to the subject.

Let's start off on the basics, a *Motor Starter* and what it does. To do that, consider a relay, any relay, such as what switches your headlights on. Then consider that you have 3 separate contacts for your 3 phases. Now make the contacts very large, from the size of a dime to the size of a silver dollar. That relay just became a "*Contactor*". It's still a relay, just a very big one. 

Now, the motor. . . A separate subject in and of itself, the reason it comes into the conversation is because most motors draw enormous current when starting. Depending on the motor and the load it is driving, that current may be 500-600%. That's 5 or 6 times the run current. Enough to melt fuses and cause the wires to rattle in the conduit. That current only lasts a few seconds, being a long time in motor circuits, but only a blip in people time. Fuses and circuit breakers aren't set up to handle that sort of current. Enter the "*Overload Deck*". . . 

The overload deck, I don't know the proper name, that's what it's called in the field, is just a specialized circuit breaker designed to handle motors and their current demands. There are many different types but most use a "eutectic" metal, one that changes from solid to liquid at a very specific temperature. These are called "solder pots" in the business. When current passes through the solid solder, it generates heat. Low current, low heat; large current, large heat. The amount of heat, determined by the amount of current, applied over a specified time will cause the solder to go euctic. How fast is a function of how much current. When the metal melts, a latch is released which causes a contact to open.

Now combine the *Contactor *and an *Overload Deck* on the same pan and you have a *Starter*. The code calls for yada, yada, yada. . . The code is a required minimum for paid installers. The "code" is put out by the National Fire Protection Agency, and updated every three or four years. Why the code comes into play should be obvious by the issuing agancy. It keeps your shop from burning down, ruining the machines, and making the spouse angry. Should you inadvertantly violate the code and have a fire, your insurance can claim an "out" and you receive nothing but a heartache. So, follow the code where you can, it pays. .

Looking at your circuit overall, you will have a 240 volt, single phase circuit feeding your shop. It will have fuses(2) or a circuit breaker (CB) in the panel protecting the wires. Not the load, just the wires. . . In your shop, there may be a subpanel to isolate the different circuits. Including a "Rotary Phase Converter". The RPC should have a starter, after all it's just a motor and a few capacitors. (and maybe a kicker motor, depenting on who built it) The output of the RPC then feeds another, 3 phase, panel if you have more than one 3 phase load. From there, you feed the lathe, which may well be a system in and of itself. For a large, as in a repurposed industrial machine, there will be the main disconnect. That may or may not consist of a contactor and control circuits. It may well be just a (very large) switch. From there, you will have the *motor circuit*, including a *starter* and various controls.

What you are asking after is implemented with a latching, normally closed control switch, fairly light, interupting either the incoming line (a contactor) or better still interrupting the *starter*. This is easily accomplished by wiring the switch in series with the coil of the starter. And you're done.

This entry is approaching the length of a small book. For this, I also apologize. Electricity is a deep subject, where you can study a lifetime and not learn it all. I'm living proof of that. . . Finding an electrician today is a challenge, many of the "electricians" licensed by the state are nothing more than "wire men". Do it right up front and it probably will pass inspection. The "code" will tell you what is right, you just need to understand the language. Hence my introduction above.

Bill Hudson​
.


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## nnam (Feb 14, 2021)

There is a 5hp starter for $58



			https://www.amazon.com/dp/B002LVUWIG/ref=cm_sw_r_cp_apa_fabc_E4TT4PXFVR12Y4HP8W9Z?_encoding=UTF8&psc=1
		


and 10hp for $75



			https://www.amazon.com/dp/B002LVUWJ0/ref=cm_sw_r_cp_apa_fabc_2WSEDERMQHPYS2D1GWPA?_encoding=UTF8&psc=1
		



They both have an adjustable overload circuit dial.  It appears to be a straightforward inline set up.


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## Canus (Feb 14, 2021)

Bi11Hudson,
Thanks for your detailed reply.  I really appreciate it.  In the attached drawing of a motor starter circuit, which would be the correct location for the E Stop switch?  I am thinking "A".  Also, should I have either fuses or circuit breakers between the RPC and the motor starter?  If so, what amp size?  This lathe has a 2 HP motor.  Thinking 20 amp.
One more question please.  If I install a motor starter do I connect it between the RPC and the rotary switch (don't think so) or between the rotary switch and the motor?  If the later, do I use the rotary switch to control forward/reverse operation by swaping two leads on the input to the contactor?


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## Bi11Hudson (Feb 14, 2021)

Sir; I cannot find any attached drawing. We will have to walk through this with text. First question, am I to understand the motor is a two speed machine? In answer to your question,* yes*, there needs to be a starter between the motor and the RPC. To clarify, assuming a two speed motor, the way the motor is wound will determine how much current is involved. This then involves a separate overload deck for each possible configuration. Which then involves a separate contactor for each overload device.

But, for a small motor you describe as a two(2) HP, we don't need to get overly complex. A single *contactor *will suffice for the E-Stop function. A *single* overload deck will be useless,  we will depend on the existing fusing there. Having the contactor close to the machine will be preferable. It even would be possible to have it between the motor and the reversing switch. But, the wiring for a two speed machine is somewhat complex, so it's best to leave that alone and install the contactor between the RPC and the machine. I'm getting wound up again, need to slow down to the non-electrical level again. Sorry. . .

The reason for locating the contactor close to the machine is to allow a future install of "dynamic braking", should you ever opt for that. Or any other control functions you may desire. The basic wiring for the contactor will revolve around a "three wire control" circuit. A *START* and a *STOP* push button. These are low current devices, connecting to the coil of the contactor. The *START* button will be a common push button, often green in modern usage. The *STOP* button will be the latching, "mushroom" head, normally closed device. Such are available from any electrical supplier. I offer a link through Allied simply because I am familiar with them. I point to 22mm panel mount devices. There are many sources, and many configurations for E-stop controls.


			https://www.alliedelec.com/product/eaton-cutler-hammer/m22-pv-k01/70059351/?referrer=search
		

In any case, do not use "dime store" switches for serious machines. Be sure to use industrial grade devices.

Given time, I can develop a "ladder" diagram suitable to your situation. If you desire, please feel free to contact me through Email if you need that level of assistance.

.


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## Canus (Feb 14, 2021)

Sorry Bill  Forgot to attach.  Here it is.  Motor is single speed.


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## Bi11Hudson (Feb 14, 2021)

Your diagram looks like a redrawn manufacturers diagram. Using such a diagram requires some familiarity with the specific equipment, which I don't have. Even different models from the same manufacturer have different configurations. A ladder diagram is much easier to read. I will draw up a "generic" diagram and forward to you in a couple of days.

Somewhere is a "3 wire" control station, the *Start* and *Stop* buttons. Where that station connects to the coil is where you want the *EStop* button. In its' simplest form, replacing the Stop button with a latching button will provide for basic interruption. There are several places where controls can be located, especially if there are several EStops. Wiring is simple for multiples, they are simply "daisy chained", all in series. At the root though, trouble shooting can be difficult or worse. Planning would pay dividends in that.

It does help that the motor is single speed. I don't know how I got it set in my mind that you had a two speed motor. I am getting old(70) and more easily confused, I guess, That sounds good, anyway, even if it isn't right. Because the machine and the RPC are cord connected with plugs, they both are exempt from many aspects of the "code". Not all, and good workmanship does still matter. But many parts of the code do not apply to portable equipment. 

I will forward a diagram of what I *think* will apply in your situation in a couple of days. Then we would have a "common ground" from which to talk.

.


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## Papa Charlie (Feb 14, 2021)

If that is the switch you have or plan to buy, then A is correct.

But you could use B too. They both accomplish the same end result, but I would feel better seeing that mfg description of the two options.


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## Canus (Feb 14, 2021)

Thanks Bi11 I really appreciate the time and effort you are devoting to assisting me.  The drawing is indeed a redrawn manufacturers diagram.  I was assuming the connection shown as "A" would be the connection that activates the contactor.


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## Larry$ (Feb 14, 2021)

I haven't seen mentioned but a big safety advantage of using a motor controller is: should you loose power the motor will not automatically restart when power returns. You will need to push the on button again. If your power went off for a while and then returned while you were changing chucks or something it could be really nasty. Motor controllers will prevent that. Over the years I've bought quite a bit from Automation Direct. Good stuff, reasonable pricing and good help if you need it. As for electricians, most don't have a clue when it comes to controls.


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## Bi11Hudson (Feb 15, 2021)

I apologize for the delay, I have several reasons for it, none of which would mean anything to you. I include an elementary diagram of what I perceive your system to be. The overview drawing is essentially 11 by 8-1/2 inches. When viewed with a PDF reader, it can be expanded and scrolled as needed.

The largest is my perception of your RPC. I show several motors connected, disregarding any control functions. Your's may be different, it is primarily an overview. The rotating element is shown as a "delta" wound motor. While it gives a more balanced output, a "wye" motor will otherwise work just as well.

The center diagram depicts what I recommend for the power circuits. There are multiple locations that would be suitable for location of the reversing switch. I would recommend the rightmost location as it is most suitable for further modifications.

The smallest drawing depicts the recommended control system. It may be powered from the line side of the starter with 240 volts on the buttons. Or, it can be powered with low voltage, 24 volts being quite common for industrial installations. If low voltage is used, "L1" and "L2" on the control diagram would be changed tp "X1" and "X2".

Further, the "ESTOP" buttons have "mushroom head" operators and latching mechanisms. I picture them mounted on either side of the machine so one is accessable whichever way you run from a crash. There are "rope" operated switches designed for use along conveyors that could just as easily be used, albeit a little more costly. The type resembles a limit switch, but with a latching mechanism.

Also, there are references along the edge so that a question can be pinpointed. Let me know what you think. . .


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