VFD estop wiring

[MrFluffy]

So I'm just commissioning the vfd on my lathe, and wading through the manual it has both a E-Stop and Fast Stop contactor input. They both need to be not activated to spin the motor.

Now from the detail fast stop appears to bring the spindle to halt even quicker by applying the external braking resistor to bring the speed down quicker whereas e-stop just cuts power to everything, I can see the fast stop being handy for reversing when threading and leaving the leadscrew engaged instead of the stock clutch/brake setup and relying on that brake to stop quick. I have always wired e-stop to my oh-poo big red switches as I was under the understanding that e-stop was the quickest method to dead stop the spindle when something went wrong, but then I've never had a vfd with a seperate fast stop to manually trigger either.

I suspect I'm going to end up wiring in a second switch, so I'll wire the original lathe stop button to the fast stop as I've dumped the original electrical gear as its been bodged by whomever did the single phase conversion on it, and add a big red button to control e-stop if its correct, but which would be the correct way to wire this?

 

[Seadog]

The stop function can be set to control the ramp down rate, i.e. deceleration, of the motor. This is controlled by injecting dc into the motor below a certain voltage. This induces a back emf which opposes the rotation, hence you can have fast stop under the control of the VFD. I haven't yet wired in a kick switch to my lathe, and probably won't get to do it either. The acceleration rate can also be set. I often just flick the motor into revrse when threading. You do need to keep your mind on the job in hand though.

 

[rikrobson]

I wired My oh-poo big red switch in the control path so it stops the motor. its pretty quick to doit. obviously there is going to be some rotational momentum in the chuck. All a resistor in the way is going to do in recuce that a bit. If you had alot of mass and there was a flywhell then there maybe a need for it. There should also be a setting for down ramp. which will force the motor to slow down quicker.

 

[rikrobson]

@Seadog beat me to it

 

[Agroshield]

...I'll wire the original lathe stop button to the fast stop... and add a big red button to control e-stop...

As the others have said, your plan is correct. Your big red button should be a latching one.

You also need to have a quick look in the instructions concerning how to restart once one or other of the two stop functions have been activated.

On the fast stop, I suspect you just hit the 'go' button and carry on. The fastness of the stop should be configurable. Setting it too fast or with too big a flywheel in the chuck will lead to the VFD faulting out and the braking effect being lost.

On the E-stop, you should have to reset/reboot/power cycle the VFD. In other words, to recover from an E-stop should require slightly more effort than a normal stop.

 

[MrFluffy]

Cool, thanks all. Wiring will proceed hereon as planned.
I did have a browse at the drive manual but its hundreds of pages thick and made my head spin in places, but most of it boils down to how to program the functions or write programs that will be executed and upload them via its serial interface and how to run it via autotune. Yes ramp and decelleration config is accessible via the front panel controls without hooking up to a serial connection. I don't think I'll be getting into hooking it up to a laptop for anything too fancy though. I've also found a big braking resistor encapsulated into a large heatsink designed for the job because I bought two for my cnc mill to brake its vfd spindle, but have to check its the right spec for this drive.
Yes my big red button is a latching in variant. Its the sort that pushes the nc microswitch inside and needs rotating to reset back to operational.

My current main problem it seems is the motor has to have a abc encoder hooked up also, and none of the 3ph motors I have have one, but so tonight fitted a 2.2kw one without for now and put 4 poles in the config as its not marked on the motor plate but p=r/f so p=(120*f)/plate rpm = (6000)/1350=4.
I ordered a encoder off the bay of fleas a couple of days back so cracking on with some other stuff while that meanders here but there's no way it seems to put the drive into feedback from the phase pulses like usual and the book does specify encoder mandatory, so for it runs at 10% speed which was enough to set up the drivetrain alignment then errors out with a speed feedback error before making a attempt to ramp up. Reverse and jog work though. Think it'll be worth the effort in the end.

 

[Agroshield]

My current main problem it seems is the motor has to have a abc encoder hooked up also...

For my education, what is an abc encoder?

While you are waiting, could you use a simple opto. switch looking at a blob of paint on the motor shaft (one pulse per rev.), or maybe onto the fan blades (more than one ppr)? Have a look at Tony Jeffree's Taig lathe pages (revmaster) for inspiration.

 

[daleyd]

What vfd is it - apart from servo drives its unusual for them to specify encoders as being essential, usually they are all set up to run open loop, though with most you can optionally connect an encoder or some sort of feedback device if wanted.

As above - quick stop for a vfd means a specified ramp down, for big stuff this is generally quicker than a coast stop. As an example I used to commission paper reel splicers for the newspaper/magazine printing business - if there was a power cut and a 3 tonne reel was spinning at full speed it would take more than 10 minutes to stop, spewing paper everywhere. Under controlled stop conditions the drive could stop the same reel from the same speed (while maintaining tension) in <10 seconds.

If you decide to go with an emergency stop that cuts power then try and put a shroud or something around it - drives don't generally like having power removed when they are operating. When I get round to doing my lathe that's probably the route I'll go down - start button, stop button (normal stop, probably configure it for a 10 second ramp down or adjust it with a bit of trial and error rather than just a coast stop) and maybe a shrouded emergency stop to take power off in case of an "ohmygodwhyisitdoingthat" moment.

 

[Agroshield]

If you decide to go with an emergency stop that cuts power then try and put a shroud or something around it - drives don't generally like having power removed when they are operating. When I get round to doing my lathe that's probably the route I'll go down - start button, stop button (normal stop, probably configure it for a 10 second ramp down or adjust it with a bit of trial and error rather than just a coast stop) and maybe a shrouded emergency stop to take power off in case of an "ohmygodwhyisitdoingthat" moment.

The E-stop should never be wired simply to cut the power. It should also not be shrouded.

If you have some reservations about 'accidental' triggering, why not put it in a safe, behind a locked door, in another room? Take a moment to think about the purpose of the control and reconsider...

It should always be wired to the dedicated E-stop input of the VFD. The danger with wiring it to cut the power is that when released, it restores the power. The VFD E-stop needs other action in addition to its release in order to get things moving again.

 

[MrFluffy]

Its a eurotherm vector 620, the drive comes in encoder and non encoder variants but it was a steal pricewise vs buying one that supported non encoder mode.
A ABC I think has 3 feedback wires and a high count per rev, I have built a revmaster and that's going on the spindle itself but a simple opto circuit won't cut it for the vfd
Agri, I'm wiring estop button unshrouded to the estop input, vfd don't act too happy about sudden load disconnects etc I know...

 

[WorkshopChris]

It should always be wired to the dedicated E-stop input of the VFD. The danger with wiring it to cut the power is that when released, it restores the power. The VFD E-stop needs other action in addition to its release in order to get things moving again.

A vfd unless built into a plc with with full safety functions should always configured not to start upon power up or repower.

 

[MrFluffy]

It doesnt, if it is power cycled or put into e-stop, it sits there with the startup banner on the display until you put it into local mode and press the go button. Equally if you hit fast stop, it wont restart the motor until you hit the start button function.
But I think this is what is said already, just stated a more obvious way.

 

[daleyd]

The E-stop should never be wired simply to cut the power. It should also not be shrouded.

If you have some reservations about 'accidental' triggering, why not put it in a safe, behind a locked door, in another room? Take a moment to think about the purpose of the control and reconsider...

It should always be wired to the dedicated E-stop input of the VFD. The danger with wiring it to cut the power is that when released, it restores the power. The VFD E-stop needs other action in addition to its release in order to get things moving again.

I think we have crossed lines about an estop and a quick stop, there's of course no problem with having a quick stop wired as you say as it's the quickest safest way to stop the machine - if you have a circuit which cuts power then you'd probably fit one of these over it...

Mr fluffy I work for eurotherm if your stuck for any info.

 

[MrFluffy]

Its this type and its going here and will just be wired into the logic for e-stop, its a place that will never get accidentally pressed in use. To disconnect the entire thing from the supply, the mem 3 phase flipswitch on the wall deals with that.

Thanks for the offer of assist daleyd, hopefully a few more days of keeping the massive manual that arrived with the drive in the toilet library for thinking sessions will be enough to sort out any lingering questions, but if not I'll be in touch.

 

[daleyd]

Looks like your all sorted!

yeah for a "quick stop" there's no need to fit a shroud, on mine I'm going to use a contactor and reset button (with the shrouded estop) like an nvr for the whole machine, in the event of any power cut then you'll need to reset the contactor to put power on to the drive. Probably (certainly!) overkill for a lathe but who doesn't like a big red button and things that go clunk? (Plus I have loads of contactors and buttons lying around)

Then I will have the start/stop/reverse and probably the quick stop on either a pendant (magnetic) or small control station on the lathe. It's all pie in the sky at the moment until I get the next 2 weeks offshore out of the way but one day....

 

[MrFluffy]

Ok, finally after a agonizing frustrating wait the post arrived with a encoder. The "3 phase" encoder has arrived with the usual level of documentation (ie none) and less wires than in the shot of it online, which after studying symbols on wiring has lead to another problem.
The eurotherm minimum mandatory wiring to work diagram for the encoder input wiring shows the phase wires from the encoder as A, _A, B, _B, +15vdc and 0V.
The encoder that has arrived, hasn't got a _A or _B wire, just A,B,Z, +VCC & NC. I understand it as Z gives a pulse once per rev for rpm output, and A & B are the phase wires.
I found note that it is a "NPN" type encoder also, I think that means npn as in transistor npn type and its how its doing its switching inside to generate the signal. From what wiring diagrams I have found on the net, it looks like 0v is also the gnd for the signal output wires for this type, and therefore should I connect _A and _B to 0v to complete the circuits? Where does that leave NC in this case? is it just a extra shield ground or should that be the _A,_B return wire path?
I dont want to risk blowing up the vfd with a assumption right now, so is there someone who can confirm which way this should be hooked up that would be helpful. Anyone?

 

[MrFluffy]

More reading has shown up a subnote on of the other sections saying if its a single ended encoder, to bond its _A and _B to the 0v terminal. So I've done that, and its still not working or the drive seeing rpm.

By not working I mean it still only rotates about 120rpm despite the speed dialed in, even in autotune. Ive checked the vcc terminals have dc voltage on them, so I guess the next stage is to drag the scope out and see if I can see a output from the encoders.
Because this vfd is new to me but secondhand and it seems like a bit of a complex beast to set up correctly fully, I dont know if the issue is the vfd, the encoder or some setup parameter so may be barking up the wrong tree anyway :/

Edit, I just went back to the auction I bought it from, and the one they sent has a different amount of wires to the one I originally ordered and there's no Z output on the one that turned up. They sell the ones without Z also for a vastly cheaper price, so looks like they sent me the cheap one and charged me for the more expensive one. Z output is as I understand it, a pulse that happens once per rev so systems can see rpm of the motor its on, and that might matter lots because the diagnostics are showing the motor at 0rpm...
While I'm not sure if this is the issue yet, I am pretty annoyed at it, and am currently waiting to see their response before setting the dogs of very bad feedback on their account.

 

[MrFluffy]

Well, my trusty old oscilloscope confirms a quadrature pulse output of about 1.2v coming out the two phase wires that goes up and down in frequency when I spin up the encoder with a cordless although describing them as square shaped would be a bit of a liberty, so options are the vfd needs something doing to cope with a single ended encoder input, or the Z pulse is mandatory (although it only shows that wire connected in one of the three diagrams in the manual for a slightly different model) or the vfd itself is sick.
Brew, warm up and thinky time again...

 

[Luke]

Quadrature should be 5v or 24v, and nice and crisp.

NPN is unlikely to be suitable. You don't say what the inverter is ( or I have missed it) but most will expect 'sinking' inputs, not 'sourcing'.

A lot of inverters can be switched to V/f or sensorless vector, so they don't have to use an encoder.

Luke

Edit: just found eurotherm vector 620.

 

[Luke]

Have just read the manual and seen that the drive supplies 12v for the encoder, not 24v or 5v, which are the more modern standards. However, the drive accepts both 5v and 24v logic levels. Have a look at table 1.8 in the manual.