E-stop and Teco VFD's

[neksmerj]

For those new to the forum, I purchased a special Teco VFD from Drives Direct in the UK.

When I say special, the VFD is a standard unit modified to run from a 240V 1-phase input, and have a 415V 3-phase output.

The question of E-stops has come up from time to time, so I dropped Drives Direct an email, it reads as follows

Hi Dave,

Recently I purchased a 240V 1-phase to 415V 3-phase 1 HP VFD for my Arboga milling machine.

My question is where to install an E-switch?

I know that there can be no interruptions between the VFD and the motor, so that only leaves the 240V line in, or is there another way?

Kind regards,

Ken

And his reply

Hi Ken,

YES there is another way, if the ES switch had a normally open contact then just connect it between the 12V and SP1 terminals of the inverter and set up the function of SP to ES with the DSP FUN function,

If the ES is normally closed(the normal way) you can still do this with the addition of a 1K resistor, connect the resistor between the 12V terminal and SP1 and the ES switch should be connected between SP1 and 0V and that will then work fine,

The software setting parameter is F19 and that need to be set to a value of 3,

I hope this helps,

Many thanks

dave.

Stu, does the above make sense to you, I'm a bit confused.

Ken

[Anorak Bob]

KJ,

Why don't you hook up the VFD to the mill and at least see if everything works as it should before you start finessing with the controls? You'd be spritely enough to leap out of the way if things turn bad. Just remember to roll the sleeves of your cardigan up.:D

BT

[Cliff Rogers]

...


YES there is another way, if the ES switch had a normally open contact then just connect it between the 12V and SP1 terminals of the inverter and set up the function of SP to ES with the DSP FUN function,

If the ES is normally closed(the normal way) you can still do this with the addition of a 1K resistor, connect the resistor between the 12V terminal and SP1 and the ES switch should be connected between SP1 and 0V and that will then work fine,

The software setting parameter is F19 and that need to be set to a value of 3,

...

That is pretty much I said the first time.

[Cliff Rogers]

Here.
http://www.woodworkforums.com/f65/wiring-vfd-arboga-mill-132429/#post1287777

[neksmerj]

Thanks Cliff,

I was hoping Drives Direct would suggest putting an E-stop in the 240V line in, but they didn't.
To me, this would seem logical. An E-stop here would kill everything.

Ken

[Stustoys]

Ken,
That's a neat trick, both his answer and getting an answer from him ;)

Chris,
Your explanation is about how to us a NO E/stop circuit, adding the resistor lets you use the more normal NC E/stop circuit(of course if the 1kresistor fails you're stuffed).

Stuart

[neksmerj]

Stu,

I agree. In a preceeding email from Drives Direct, they say they have just moved into their new premises. How long's that been, 12 months?

Nice to see the service has improved dramatically.

Ken

[Greg Q]

Thanks Cliff,

I was hoping Drives Direct would suggest putting an E-stop in the 240V line in, but they didn't.
To me, this would seem logical. An E-stop here would kill everything.

Ken

Eventually yes, but the capacitors probably hold enough charge to keep the motor going for a few seconds even without mains power.

[neksmerj]

Thanks Greg,

I obviously don't know how VFD's work. I assumed that if you shut down the power, the motor would come to fairly hasty stop.

Maybe an even dumber question, is an E-stop or red schidt button, really necessary?

Ken

[ozengines]

Are you sure you have a 240v 1phase to 415V 3phase and not 220v 3phase?
You should have forward-stop-reverse buttons on your VFD, usually the forward and reverse is a closed contact and stop is open, it is on mine. You can use a SPDT center off switch.
You can setup the start for soft start and the stop with quick braking. I like a quick stop in case of emergencies. Although on my first setup for quick stop I did not realise my large 4 jaw chuck was not on tight and when to VFD pulled up quick the chuck nearly spung off. lol

[ozengines]

You can adjust the stopping speed by programming

[Greg Q]

I think that installing an e-stop is like a dog _______ his ____. He does it because he can.:wink:

I don't have an answer for you on that. Current standards would require one if you were going to install a machine commercially I think. How much of that is relevant is up to you. Myself...I jabbed myself in the eye once with a cotton ball. Do the maths...:-

[neksmerj]

Greg,

Good point. I sometimes wish my tongue was that long, if only to lick my eyebrows.

Ozengines. Oh yeah, my VFD is definitely 240V in to 415 out. As mentioned above, it's a special.

AB, you suggest just hooking it up, to be honest, I'm apprehensive. I'm afraid I'm going to fill my mate's shed with acrid white smoke. Who am I kidding, maybe this week I'll give the Arboga a whirl, and I will take my camera, if I ever get it back from Greg.

Ken

[Cliff Rogers]

Thanks Cliff,

I was hoping Drives Direct would suggest putting an E-stop in the 240V line in, but they didn't.
To me, this would seem logical. An E-stop here would kill everything.

Ken
But as I said... "If you put it in the 240V line, then when you hit it, the power to the controller would go off & the motor would free wheel to a halt."

If you wire up an emergency stop via the controller, then it will stop faster.

The 2 VFDs that I have both have a big red stopper that will stop the motor in 3 seconds.
Both also have an isolation switch in fairly easy reach that I can turn off if smoke starts coming out of the motor or the controller.

[Stustoys]

The 2 VFDs that I have both have a big red stopper that will stop the motor in 3 seconds.
Both also have an isolation switch in fairly easy reach that I can turn off if smoke starts coming out of the motor or the controller.
If you feel isolation is likely to be a problem, this is the way I would go about it. (although I'm still not convinced about braking on the VSD I have with machines the size of mine)

Its possible you could cut the 240V and activate the E/stop on the VSD at the same time. But that's not something I would like to do often.

Stuart

[Ropetangler]

Firstly I should preface my comments by saying that I am well outside my area of qualification and expertise, and the statements following are as I understand the situation to be, and if I am wrong, I hope that someone who is full bottle on this topic will put me straight.
The reason why the E Stop would not be in the power in side of things is as Greg has said, the input capacitors store significant energy which would allow a motor to run on a bit, But also the VFD is capable of dynamic braking the motor, and to do that it needs power. A bit like stopping a car travelling along a road, by just knocking it into neutral, sure it will eventually stop, but nowhere near as quickly as if you applied the brakes at full pressure, but with ABS active. If the VFD still has power at the input terminals, it can activate the program which it has been set up to do, in the event of certain defined circumstances. If there is no danger of say a chuck unscrewing as Ozengines experienced, you can program it to stop very quickly, perhaps well under 1 revolution from full speed. For an emergency stop, this could be a very useful feature, if say someone was being drawn into the machine by loose clothing say, but any chuck would want to be locked to the spindle by some means and not just screwed on without any locking system.
If you have a screwed on chuck, then braking force has to be more limited, and the risk of not being able to prevent injury because of a slower stop balanced against the chance of a chuck unscrewing at speed, and chasing people around the workshop.
Depending on your VFD, you may have more than one stop mode, and therefore still be able to program the normal stop function to be a much gentler stop, maybe stopping from 1450 RPM to Zero in around 20 revolutions say, still quite a quick stop, but much easier on the drive train. Naturally this is the stop button for normal stopping of the machine, and the Emergency stop should not be used except in emergency situations. If you only have one stop mode, you have to compromise one need against the other.
Regarding the way you can use a 1000Ω resistor and a normally closed E stop switch to function as Dave has described, it sounds to me that the control is a high input impedance device, probably using a Field Effect Transistor, or Fet. Fets are voltage controlled and draw (virtually) no current, whereas normal bipolar transistors are current controlled. The 12 volts applied via the 1K resistor, and a current of 12 mA flows to ground via the E stop switch, SP1 is held at zero volts and so the device runs as per normal, but when the E stop is activated, the link to ground is cut, and the input terminal, SP1, will float at 12 volts which switches the motor off and applies the pre-programmed amount of braking on. As this resistor will be dissipating only 144 milliwatts, a half watt resistor will have a low chance of failure I would think.
That's quite enough from me, if I'm off the mark in my understanding of VFDs, please someone put me straight. For now Cheers all, and Ken I will get that book in the mail tomorrow I would hope,
Rob.

[neksmerj]

RT.

That's a nice concise description, something I could understand.

Will do my banking tomorrow, and initiate an EFT for the book.

Many thanks,

Ken

[wbleeker]

Ken
When you got your VFD from Dave did he give you a price that didn't include VAT? I got a price from him for one to do a 2hp 3 phase motor but it was including VAT, I have emailed him for another price without VAT but not heard back yet.
Will