shunt trip breakers

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Zorak

Zorak

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I was wondering if it is considered good practice to wire in series several shunt trip contacts? If you have several shunt trip breakers that are all going to be closed by the same signal, can that wire be run in series with all the contacts or is it better to run a single pair of wires from a contactor to each shunt trip breaker?

Thanks in advance.

Z
 
Z, welcome to the forum! :)

Let's start with the fact that shunt-trip breakers are opened, not closed, by a signal voltage. The tripping wiring should all be wired in parallel.

If you're talking about using auxiliary contacts for remote notification, then it can be done either way, depending on the signalling circuit used.
 
Larry, thanks for the reply and yes, I did use the wrong term. They are to open.

It is probably the second most writing error I do, mixing up terms, especially opposites. The first is similiar but happens more often. I'll be typing along, thinking exactly as I am wanting to say, such as, "the power is not to blah blah blah" but I about 50% of the time do not actually type "not" even though I was thinking it. And then the confusion begins. Let the good times roll.

For this particular application, we could have up to 10 VFDs and wanted to have a way to handle any emergency stop situations, even if the VFD is manually being run. The distance from the panel to VFD is not great, but was curious on putting the contacts in series. In parallel will not be an issue. I'll just have a source go through the safety relay to a set of terminal blocks then out to each individual shunt trip breaker.

Thanks again.

Z
 
Again, what contacts do you mean? Most shunt-trip breakers only have tripping coils, which should all be paralleled if simultaneous operation is desired.
 
Larry,

Again, I am sorry. There is a coil, but it has always been viewed in my mind as a contact. I know it is wrong and the terminology can confuse, for which I am sorry. I do not deal with them all that often (the last being over eight years ago), that I have trained myself to think otherwise.

Thanks again for the information.

As for using an input to the drive for an emergency stop, the drives we would be using are ACS550s. They allow this function (though I do not think it is safety rated), but the customer is a farmer coop which has members who, as some members have displayed (no offense to farmers), do not trust the electrical gadgets we are suggesting should be added to do what they want. Though more expensive, I think they would feel better with something that interrupts the input feed rather than trust a chip to do it.

Again, thanks for your time, your patience with my writing skills and terminalogy, and for being willing to help.

Z
 
As I often do when wiring commercial-kitchen fire-suppression systems, especially in existing installations where there are no shunt-trips, maybe you can use a contactor, which will drop out if the supply is broken.
 
All the VFDs will be 40 hp or greater with the largest looking to be 100 hp. And there could be up to 10 of them. Instead of trying to get these drives in a MCC section, they are most likely going to be wall mounted and feed from the distribution panel across the room. Since a new breaker would have to be bought anyways to accomodate this, I was thinking that the adder for 10 shunt trip accessories would be the cheaper way to go versus buying contactors, finding the room to place them, and then wiring them. (Though I have not done any actual pricing to prove this)

However, again, I appreciate the idea. The collective experience here is wonderful and I thank you all.

Z
 
If the drives sre supplied by a single panel, it might be cheaper/easier to use a single shunt-trip main breaker.
 
Zorak said:
I think they would feel better with something that interrupts the input feed rather than trust a chip to do it.
Click to expand...
But they will be OK knowing that if the control circuit is lost for ANY reason, the emergency stop system WILL NOT WORK!

Personally, I don't care for shunt-trip breakers in an emergency stop operation unless you have an alarm that goes off if the you lose the e-stop control circuit (I still prefer a NO contactor).

I would say a shunt-trip breaker "fails closed" and a contactor fails open.
 
Zorak,

One point of confusion is that the industry uses the term 'series' in ways that are electrically incorrect.

For example, if you feed 10 receptacles by going from the first to the second to the third, many would call that 'series' wiring, even though the fact is that each receptacle is being feed with the full circuit voltage, and thus the receptacles are electrically in parallel.

A shunt trip is a device powered by some control voltage. If you have 10 shunt trip devices, then they all need to see the proper control voltage. Thus the devices must be electrically wired in parallel. You can jump from one device to the next (like receptacles) but you must arrange your connections so that each device gets the full voltage. If you connect the devices in series, then they won't function or won't function properly. (The common example is someone wiring a set of lamps in series, where the voltage gets divided between the lamps and they end up very dim.)

Regarding the comment about using shunt trips for safety, and what happens if the e-stop circuit goes: this is a real problem; if you don't have power to operate your shunt trip, then your e-stops won't open the circuit. Another solution is to use an 'undervoltage trip', which is conceptually the opposite of a shunt trip: it trips the breaker if the control voltage is removed. But the best solution is to realize that you are now in the realm of engineering a safety system, and tread carefully.

-Jon
 
winnie said:
Regarding the comment about using shunt trips for safety, and what happens if the e-stop circuit goes: this is a real problem; if you don't have power to operate your shunt trip, then your e-stops won't open the circuit.
Click to expand...

A great point, I do not believe it is an acceptable practice to wire motor emergency stop circuits using a shunt trip breaker.

I think it would be in NFPA 79.
 
The drives would be supplied from a panel section attached to a 4000A service. And with close to 400 hp of motors, the cost of a distribution panel would be high.

As for the other comments, they are exactly the same things I have thought of. I want this to work all the time. This is a safety circuit afterall. It does no good if it does not work. When I first posted my question, my idea was to have a hot control circuit run to each breaker and trip when the control circuit opened up. I still considered it a shunt trip for lack of a better term at the time because I did not yet know of the undervoltage trip, which I found out a day or so later and am currently having a Square D rep find out whether it will do what I want it to do.

Thus, from my standpoint, then, regardless of whether there is an actual Estop or a power failure in the control circuit, the drives shut down. Incorporated in this is a series of dual channel Estop buttons and currently five AB 700S-P contactors. Two of the contactors are used at the ends of each channel of the Estops, along with hold and reset contacts. One is used for a reset. And the remaining would used to open up starter (the VFDs are not the only motors) and shunt (undervoltage) circuits with each circuit going through a NO of each contactor. Plus some other contacts here and there.

This then allows the drives to be shut down regardless of whether they are in auto running or manual running. Likewise, the other motors, controlled by starters would also be shut down, regardless of whether in hand or auto control.

I can provide the control circuit, as I see it now with the use of shunt (undervoltage) trip if you would like to see it.

I am not afraid of spending money and when it comes to safety, you cannot base anything on money, however, if you have to buy the breakers to feed the drives anyways, and the use of a shunt (undervoltage) trip meets the safety required, then it is a cheaper way to go as the adder is far far less than the labor and material for ten 30 hp to 100 hp contactors.

Please also do not see anything I have said as being defensive. I welcome your comments. I am merely trying to explain what I am trying to do and the reasoning behind it.

I again thank you all for your time and thoughts.

Z
 
Any scheme using either the integrated options of a VFD or using a shunt trip system are inherently unsuitable as a safty based EPO system, because they are not fail-safe.

A contactor with push to break EPO buttons is the only simple and safe EPO system.

You can build more complex EPO systems, but you need to do it using safety critical rated components, see Pilz.
 
dbuckley said:
Any scheme using either the integrated options of a VFD or using a shunt trip system are inherently unsuitable as a safty based EPO system, because they are not fail-safe.
Click to expand...

The E-Stop function of the drive is failsafe, the manufacture would be in big trouble like Toyota:roll: If it wasn't.:D
 
hillbilly1 said:
The E-Stop function of the drive is failsafe, the manufacture would be in big trouble like Toyota:roll: If it wasn't.:D
Click to expand...
Far from convinced.

Where I grew up, an emergency stop is required to positively interrupt to supply, and asking a VFD to stop through a control input doesn't reach that standard.

Add to that, on those VFDs I've seen which have an emergency stop input, they are active high inputs, so if you wire a bunch of paralled normally open pushbuttons to that inoput, and failure in that entire mechanism will cause the estop signal not to arrive at the VFD.

So whereas this sort of estop can (and probably will) work, it can also fail, and when an estop that stops motors that are a danger to life fail, litigious things happen, and, in my opinion, quite rightly too.
 
dbuckley said:
Far from convinced.

Where I grew up, an emergency stop is required to positively interrupt to supply, and asking a VFD to stop through a control input doesn't reach that standard.

Add to that, on those VFDs I've seen which have an emergency stop input, they are active high inputs, so if you wire a bunch of paralled normally open pushbuttons to that inoput, and failure in that entire mechanism will cause the estop signal not to arrive at the VFD.

So whereas this sort of estop can (and probably will) work, it can also fail, and when an estop that stops motors that are a danger to life fail, litigious things happen, and, in my opinion, quite rightly too.
Click to expand...


True E-Stops are always series wired, removal or failure of any part of the circuit will shut down the control circuit. The E-Stop function of the drive works just like the E-Stop of a standard magnetic starter, removes the control voltage, it fails off. Since each drive has its own control voltage, a dry contact from a electrically held relay would be used, with all of the relays wired to fail "open" The E-Stops would control the relays. It is exactly the same way magnetic starters are controlled if they are on different control power.
 
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