Inverter vfd's do's and dont's

Recent conversations around inverter installation on mills and lathes prompted me to add this link...

http://m.machinedesign.com/motorsdrives/feed-your-vfd-right-power

LINK

It is written by someone who works at Lenze, so is not hearsay, what my aunty told me as a school boy or any old fish wives tales.....

Have a read and make up your own mind.....Do heed it is written in American parlance too...

Edited By JasonB on 04/02/2017 16:06:48

Very interesting article, more to take in on the VFD learning curve.

A lot of info in there is covered in some of the manufacturers installation manuals, but there are quite a few manuals I have read that dont touch on a lot of its contents.

It would be interesting to see how many home installations have every power cable and every logic control cable running is steel tubing and how many are seperated by 12".

Thanks for the link John.

Thanks for the link John, very interesting reading.

Thor

Hi all,

I am guessing that this thread will have attracted the attention of all those who have VFDs. While you are are reading can I ask for help.

I have a "Eurotherm 601" VFD which works well and is connected up using the simple "Control Wiring" circuit on page 4-3 of the "Electrical Installation" section of the Product Manual. This circuit has a simple on/off switch connected across terminals 6 and 7 of the VFD to give stop and start control.

BUT I would like to be able to connect the thing up using a momentary "on" push button swich for Start and a momentary "break" switch for Stop, like the pendant controls available from some of our suppliers. Anyone got one of these VFDs and know how to connect for this?

Useful information in the link but I wonder if it was written mostly for large industrial installations, certainly I have no rigid steel conduit.

Thanks

Rod

Rod,

Without the manual, it sounds like your vfd requires a permanent input across 6&7 to run....That being the case a solution would be to use a relay...along with your momentary switches....but would need a supply to power the relay...

Some inverters have the capability to drive a small relay, for example the Teco E2 series, not sure if yours could do this...

I can sketch this up if it is what you need....?

Edited By John Rudd on 04/02/2017 17:39:24

Interesting read, the company I work for build industrial washing machines for Hospitals and Universities, our big machines, walk through's with enough space for a small car, use two VFD's, a small one to drive an extractor fan at various speeds and a larger unit to run a 3HP pump, with ramp up and down, slow running etc. They are housed in a control cabinet with a PLC and profibus cables etc and 24vdc. In the early days we had issues with the profibus being affected by the VFD so the cables were re routed, we use plastic cable trays for all and have had no further trouble.

All of the sites where our machines are installed, most of the universities in the uk and the world, have to have standby generators which are tested twice a year with all equipment running in the buildings, they give our machines no grief and as soon as the main supply drops off our machines shut down and as soon as power is detected again carry out an auto power up and restart without any problems from either power source.

The supply from the VFD to the motor is seperated by fuses and a contactor, when the pump is called to run the contactor closes then the VFD starts up, all controlled by the PLC.

Martin P

John

Thanks for your prompt and constructive reply. I had thought of using a latching relay circuit but was trying to avoid the extra complication of the necessary LV power supply.

The commercial pendant control units seem to avoid the need for relay or power supply and was hoping someone knew how it could be done for my VFD.

Once again, thanks

Rod

It should be noted that the Lenze guidelines apply to the lenze VFDs, not necessarily everyone else's products. My large Danfoss VFD specifically states that there is no restriction on switching between VFD and load. Which is good, since I use it to power three separate machines with six motors between them.

Hello Rod, I have had a look in the manual for your drive, the mode of operation cannot be changed. You could use a relay with a 240 vac coil or alternatively use the 24 vdc supply built into the drive. It is only good for 50 ma, there are small interface relays available with coils around 3 k ohms. Regards, Michael

I would not recommend using a relay with a 240 coil, this would mean the switch contacts have mains at them....not good...Even industrial control circuits dont run at this voltage level for good reason...

Even industrial control circuits dont run at this voltage level for good reason...

The good reason being that in industrial environments equipment gets abused and damaged. 24 vdc would be the better option, 240 vac properly installed and respected is not unsafe. Regards, Michael

Mark - which Danfoss VFD do you have? A VFD that allows direct online starting would be a very useful choice but mostly they say you need to disable the output before changing motors and fancy VFDs allow you to switch motor parameters at the same time. I haven't seen one like the one you mention.

Murray

It's possible to program most inverters to respond to momentary or latching switches and also NC or NO switches and whether they are switching to +V or GND. So that's six options per switch so you can imagine it gets complicated fast. My article here has some pointers for the IMO Jaguar Cub inverters.

Basically you need to read the manual carefully and identify exactly what function will do what you want (e.g the Jaguar Cub has both controlled stop and immediate disconnection stop functions - you can have both controlled by separate switches if you want). Once you have the function identified, decide which input you want to use and what switch, and how it is likely to be wired NC or NO and to which power line. You will probably need top refer to 3 or 4 different parts of the manual to track it all down.

It is possible, but patience and a systematic approach are needed, and be prepared for it to take a good while. And test it all works with the motor not connected to the machine!

Neil

Generally you can program drives to operate in what is commonly known as two or three wire operation. In this case only two wire is available according to the manual I had a look at. This is very unusual to me, I have configured many different makes and models of drives and this is the first time I have come across this. Looking again at the manual, it is probably due to the low count of control terminals available, ten, five of which are for analogue I/O. Regards, Michael.

The manual is HERE

I have a "Eurotherm 601" VFD which works well and is connected up using the simple "Control Wiring" circuit on page 4-3 of the "Electrical Installation" section of the Product Manual. This circuit has a simple on/off switch connected across terminals 6 and 7 of the VFD to give stop and start control.

BUT I would like to be able to connect the thing up using a momentary "on" push button switch for Start and a momentary "break" switch for Stop, like the pendant controls available from some of our suppliers. Anyone got one of these VFDs and know how to connect for this?

It seems to expect latching switches for RUN and DIRECTION on 7 and 8, but a momentary switch for JOG on 9.

You could wire a normally closed E-stop in series with the RUN switch on 7.

As Michael says it doesn't seem to have the flexibility of later VFDs.

You can only have one stopping mode active as well.

Neil

On a lighter and inconsequential note, about 25 years ago I commissioned a control system in Eire that had Hitachi or Toshiba drives, can't 100% remember which. They only had a four seven segment led display, the fault code for under voltage trip was F followed by OFF, made me laugh.

Can I thank everyone who has helped to answer my question about switching for my VFD. Now that several of you knowledgeable chaps have had sight of the Manual and have determined my VFD has no provision for using separate Stop and Start buttons I will use a relay as first suggested.

I will search among my (small) stock of odd relays for one which makes a good audible "clunk" when energised, Then it will seem as if I have a "proper" contactor of the type the lathe would have had when new!

I accept what Michael has said about 240v being safe if carefully handled but as I am more of an "Amateur Electrician" I will use a LV relay and fit an appropriate LV supply, I can always tap into the LV supply for additional lamps etc so it won't be wasted.

Thanks again. Rod

There's a 24V supply on the inverter which is good for 50mA, enough for a relay, although no one that will give you a massive thunk!

I have a 30 year old Hitachi VFD that doesn't even have a display. Apparently it was an optional extra. Presumably programming was by some form of external device. I guess if it tells me to f off it will do so in complete silence and I will get to replace it with something more modern.

Murray

If it can't be more polite I'd be inclined to get rid of it anyway.