Emergency stop button with a VFD ?

[m_c]

That VFD is quite a basic one, with a very basic manual, but it should be able to be programmed to do what you want.

First off, never cut power to a VFD to stop the motor. It results in the motor stopping in a random/uncontrolled manner.
If you did want to cut power, it would normally be done with a time delay safety relay, so the drive can stop the motor in a fully controlled manner, before being powered down.

As has been said, you need to wire the e-stop so it switches between the com terminal, and one of the X terminals.
You then need to set the parameter for the relevant X input (P50-55, which correspond to X1 to 6).
From the manual I've found, I think you want option 1 for an e-stop button, but possibly 2 or 4. You may need to experiment, and there is the possibility that it may only work with a NO switch, not an NC setup like you would normally implement with an e-stop.

The biggest issue with that VFD, is it doesn't allow for an external braking resistor to be fitted, so it's limited in how quickly it can stop the motor, without faulting out.

 

[Kram]

First off, never cut power to a VFD to stop the motor. It results in the motor stopping in a random/uncontrolled manner.

No, this is often the manufacturer recommended approach for a few reasons. Coasting to stop is not random. It is also reliable in the event of the drive being programmed incorrectly, a drive fault or electrical issue. Note that inductance from the motor cable can mess with the control inputs if they are too close and parallel without shielding, unlikely but it is one of the reasons InverterDrive told me.
The same coasting will happen if you use a drives E trip input as an electrically latching e stop.
I have not seen any vfd manuals with a mention of "emergency stop" in the context of human operator protection.

Simplest way to keep "fast stop" would be a mechanically latching N/C e stop button in series with the run switch.

My suggestion is, in adition to a big red e stop button on the incoming power or run switch, to also wire in a momentary N/O foot switch in series with the run switch, so that hands are not required to start and stop the machine. Its quicker to lift your foot than to reach for a big red button. Having the foot switch to run is useful for a lot of operations. The switch should be guarded to prevent items falling on it, and the main run switch should always be toggled off between operations.

 

[Turbo]

Can't you just wire the E stop switch into the power supply feed of your VFD ?

Or is that just a silly idea ?

It's a silly idea! VFD's do not like sudden power cuts to either the input or output side, after all you wouldn't switch off your pc by switching it off at the wall! Do it too often & you'll fry the electronics in the VFD!

You need to let the electronics in the VFD shut down properly before cutting any power. Use the emergency stop to tell the vfd to cut power to the output via the input terminals. Then once you hit the stop the electronics will do their thing & stop the motor. You can use electronic braking to slow the motor more quickly but don't go too extreme without fitting a braking resistor to soak up all the amps that is suddenly being dumped!

Normally you will need to push the start button to get the motor to go again after an emergency stop but not always! I replaced a vfd in a Hegner wood lathe & the way it was wired up originally meant that when you reset the emergency stop the lathe started running again! I rewired it so that didn't happen.

 

[Pete.]

I would not worry about braking the motor to a stop using the E-stop. Try to imagine a situation where you NEED to use the E-stop where the motor isn't already heavily loaded or stalled and will stop immediately. The only thing I can come up with off the top of my head is if you have long stock poking out the back of the spindle which had started to whip. Ususally you wouldn't be quick enough no matter what because by the time you've realised you're in trouble it's already bent.

Emergency braking can cause the chuck to un-screw anyway do you want the spindle stopped dead and 10kg of spinning chuck in your guts?

 

[mtt.tr]

Other issue with non coasting stops is the drives will run the machine down at a set rate if it sees a load it ups the speed to maintain the same rpm curve

So you are getting sucked it and you have a 10s slow down it will keep puling until the 10s are over.

But coasting the Motor assuming you can stop it will stop


But arguably it makes no difference if it's gone so wrong that you need the estop good chance its too late anyway.


It's not uncommon to have an estop killing the incoming power, it's and emergency your life is worth more than a vfd.

Though some are timed to allow ramp then the kill the main contactor

It's all about proper risk assessment then decided where it's best



This clears it up https://inverterdrive.com/howto/Variable-Frequency-Inverter-Drive-on-Lathe/

 

[hotponyshoes]

Could you not just get an estop button with more than one set of contacts (or the type with stackable contacts) and use an auxiliary set to add a brake resistor?

Like mr.tr just said, if you (or somebody else!) needs to hit the button you just want the machine to stop.
It will be a lot easier to repair/replace the vfd/motor/machine afterwards if you still have a full set of fingers...

 

[daleyd]

I don’t really understand the idea that an estop should never cut power, it’s quite a common thing. If you are doing it in industry it would need to be risk assessed and all the other stuff that goes with it but it’s done all the time - if it’s the best solution for the apication.

When I worked on large printing presses (newspaper/magazine printing) there were always 2 stop circuits - 1 a controlled “quick stop” which would stop in a few seconds, the other was a shrouded button (to prevent accidental actuation) that killed power to the drives. Took longer to stop but it was the last line of defence, so to speak. It’s become less common nowadays due to the fairly recent advent of drives with SIL rated inputs that can be used as a safety stop but before these were commonplace then the only way you could guarantee a stop would be to cut the power. Of course if whatever machine is going to take some minutes to stop then you probably need to build in a controlled stop - but on a home lathe I’d suggest cutting the energy source is probably your safest/easiest method - but as long as it stops reliably then it’s up to you, there’s no right/wrong way. I like the ability to cut the power as it’s independent of the drive, in the (admittedly highly unlikely) event that the drive is screwed then t don’t want to be relying on an input to stop it, I prefer an old fashioned contactor to kill it)

As well as the above cutting power on the input isn’t actually all that bad for the drive, disconnecting the load is worse. It’s not something you want to be doing as a matter of course but if you do need to do it then it shouldn’t automatically mean you’ve fried your vfd.

 

[Hopefuldave]

Ok, the VFD on my lathe is a pukka industrial unit (ABB), but loss of power to it puts it into E-Stop, remaining voltage on the DC bus capacitors is held up by dynamic braking back-emf until motor rpm has dropped to near-nuffink. It's described in the manufacturer's manual...
There's a contactor feeding power, usual start/stop button NVR set-up, with the stop button in series with the lathe's E-Stops and a Big Red Panic Button by the door so my loved ones don't have to dodge flailing body parts to stop the wet whuppa-whuppa noise...

I also put a "neutral switch" feeding the NVR ON button on the forward-stop-reverse switch, so the whole machine can't be powered up straight into motion. The fwd-stop-rev lever operates (eventually) a cam and microswitches, easy enough to fit another in the box!

Dave H. (the other one)

 

[mike os]

Estop should bring any rotating parts to a stop as quickly as possible, so needs wiring as a control function with rapid braking... think about why you would estop a lathe, you want that spinning for another 15 seconds while your arm is wrapped around the chuck or that 2kg of steel is loose in the chuck?

All breaking the supply does is stop it being powered, not emergency stop it

 

[Hopefuldave]

Estop should bring any rotating parts to a stop as quickly as possible, so needs wiring as a control function with rapid braking... think about why you would estop a lathe, you want that spinning for another 15 seconds while your arm is wrapped around the chuck or that 2kg of steel is loose in the chuck?

All breaking the supply does is stop it being powered, not emergency stop it

See above, the ABB I use does an emergency rapid stop...

The Holbrook has a pretty efficient brake mid-position on the fast/slow lever well within arm's reach, too!

Dave H. (the other one)

 

[daleyd]

See above, the ABB I use does an emergency rapid stop...

The Holbrook has a pretty efficient brake mid-position on the fast/slow lever well within arm's reach, too!

Dave H. (the other one)

That’s the same as mine (ATV312) - on under voltage trip (ie if I hit the big red button) it will perform a fast stop. Don’t know if the Chinese vfd have the same option, but I like the fact that I have a completely independant way of stopping it if needed.

 

[not done it yet]

I’m quite confident that mains trips are not going to damage a VFD - but tripping between VFDand motor is taboo - unless the VFD is a fair way towards a magnitude larger than the motor power.

 

[W.olly]

Now then to make this easier.....lol, This has gone a bit to far again. All i need is a simple answer to

1 Is it worth fitting a Estop with the VFD (single phase to three phase motor) sod the down speed malarky.
2 If so then how to wire in a Estop with the VFD. so what wires go where please

near finished the cabinet so soon to be wiring it all up

 

[Stupoty]

Can't you just wire the E stop switch into the power supply feed of your VFD ?

Or is that just a silly idea ?

the vfd can(should) stop the motor quicker than having it coast to stop , even without a brake.

Stu

 

[Pete.]

1. Yes
2. As per Kim's instructions.

Think about all the other lathes, mills, drill presses and bandsaws wtc that have e-stops but no VFD. They don't brake the machine to a halt, they just cut the power to the motor. Do the same and you'll be fine.

 

[W.olly]

1. Yes
2. As per Kim's instructions.

Think about all the other lathes, mills, drill presses and bandsaws wtc that have e-stops but no VFD. They don't brake the machine to a halt, they just cut the power to the motor. Do the same and you'll be fine.

ok, i just need to understand the wiring for it. ill read up more.

 

[m_c]

No, this is often the manufacturer recommended approach for a few reasons. Coasting to stop is not random. It is also reliable in the event of the drive being programmed incorrectly, a drive fault or electrical issue. Note that inductance from the motor cable can mess with the control inputs if they are too close and parallel without shielding, unlikely but it is one of the reasons InverterDrive told me.
The same coasting will happen if you use a drives E trip input as an electrically latching e stop.
I have not seen any vfd manuals with a mention of "emergency stop" in the context of human operator protection.

Simplest way to keep "fast stop" would be a mechanically latching N/C e stop button in series with the run switch.

My suggestion is, in adition to a big red e stop button on the incoming power or run switch, to also wire in a momentary N/O foot switch in series with the run switch, so that hands are not required to start and stop the machine. Its quicker to lift your foot than to reach for a big red button. Having the foot switch to run is useful for a lot of operations. The switch should be guarded to prevent items falling on it, and the main run switch should always be toggled off between operations.

The issue with just cutting the power, is unless the drive has input voltage monitoring, you're then reliant on the DC bus voltage dropping to the point an undervoltage fault is triggered. How quickly that happens, depends on a few different factors, which is why I said it results in an random/uncontrolled stop.
Cutting power to the VFD should be a last line of defence.

How an e-stop is handled, as has already been discussed, depends on the circumstances.
Just cutting power and letting things coast to a halt may be the safest, but often it won't be.

 

[W.olly]

where will the Estop go and is this correct ?

 

[m_c]

where will the Estop go and is this correct ?

View attachment 317973

Between Comm, and any of the X terminals. You then need to set the relevant parameter for your chosen X terminal to do what you'd like it do.

 

[W.olly]

so like so,

Then choose one of the parameters on the VFD settings, as there are two in the instruction.