Two inverter drive questions

Tim,

The first instance I don't believe will cause a major issue.

1) When powering up, the motor won't start until the input caps have charged up and the logic is ready to go, so won't be significantly different. 2) When removing input power, the caps will disharge and the inverter will trip with an AC fail. It would be neater however to have a simple enable switch on the control logic. This would preserve the life of your input contactor as you won't be removing the power with current flowing.

As for the second question, the pot acts as a simple voltage divider to provide the control voltage. As long as dropping from 2.5K to 1K doesn't exceed the current capability of the control supply you should be OK You will be looking at 24mA through the pot instead of 9.6mA assuming 24V controls This would be over 0.5W so you may need to watch the rating of the pot as well

Stuart

The manual quotes control pot ranges of 1 to 10k and the voltage is 10 volts so only 100mW dissipation on the pot. I does help to RTFM as Mark would say! Bob

Thankyou.

The reason for trying to simplify the wiring is just that the conduit carrying signal and associated wiring from the front to the back of the lathe is already stuffed to the limit. Anything extra unfortunately won't be done to the same standard, I'm not planning to add more flex conduit! The wiring from the old speed pot is already there. Also from the viewpoint of 'driving' the lathe there is no need for another control.

As I said, the speed reference voltage is only 10V, though 24V is used for the logic inputs.

Tim

No problem with switching inputs, in fact this is the accepted way now in industry to control these things. Had an interesting conversation with Siemens a while ago whilst trying to wire a big 22Kw inverter up for 3 wire stop start operation. Couldn't find anything in the 23,876 page manual so rang Siemens technical to find out, UK didn't know and had to transfer me to Germany who took about 10 minutes to find out how to do it, it wasn't obvious. Program F87659835 to 87676 and set parameter 3826498 to the same.

When I questioned why you had to jump thru hoops to wire up 3 wire I was told "no one wires up 3 wire any more, you just switch it on with a contactor "

The conversation ended when I happened to remark that even a Lancaster only had one toggle switch for start...........................

John S.

You could put a switch in the top leg of the pot (at the control box end). Opening that will force the speed demand to zero without changing the setting.

-adrian

Tim wrote:

Tim,

You are correct, ref voltage is 10V. I rushed my answer on the way out to the pub.

S.

Hi, Drives do not like frequent power cycles. The inrush due to the DC link capacitors is always a source of problems for drive designers. Normally these take the form of NTC thermistors, which are switched out when the drive CPU has booted up.

To be safe I would use the pot suggested in the manual. There will be a reason for them specifiying 2.5k.

You can use contactors, but use the drive to switch the motor. I assume this is a safety interloc while your messing with the lathe? I would not like to have someone using a contactor switching under load. The IGBT's will not like that.

Finally the RCD question. The RCD is tripping because there is a simple EMC filter in the front end, usually from the -ve pole of the DC link to Earth. The current the RCD is seeing is the leakage current from this filter. A simple way of getting round this is to disconnect the capacitor from the -ve DC link to deck. There should be an obvious statement in the manual regarding this. RTFM. The filter is there to stop conducted EMC going backup the mains to more sensitive equipment in the MHz range.

Is this running off single phase?

Rob (ex Control Techniques R and D)

It won't be switched frequently, this is a clutched lathe, but I hear what you say. As I said, I don't have the manual for this drive, only the separate manual for the control panel which doesn't give a value for the pot. The little diagram on the drive itself states 2.5K, Bob Minchin has got a figure of 1 to 10K from somewhere. I could probably download the manual, my internet link is very slow at the moment & I haven't tried. It's a trivial matter to change the pot, I just don't have one of 2.5K in my back pocket

Re the RCD question, I do have the full manual for that drive and I've found nothing about disconnecting caps as you suggest, just basically 'if you must have an RCD, use a Type B with adjustable tripping...'. I'll have another look through over my morning coffee.. I did have an old ABB drive which had a screw you could remove to do just what you describe.

Supply is Single phase via a 3-phase rotary converter, the principal reason for adding the inverter is to make starting the motor easier from cold. It sometimes takes three or four attempts without the inverter, and winter isn't here yet. The variable speed facility will be a bonus. Also hopefully I'll be able to ise the higher speeds if I need them, by engaging the clutch with the motor slowed right down & then bringing the speed up. Without the inverter, letting the clutch in to anything over 1000 rpm makes the converter rather unhappy.

Many thanks Tim

Tim,

There is a quick guide here

a couple of PDF pages so file should not be too big. For a list of other Altivar 58 related docs try $file/ATV58NTechData.htm HTH

Bob

Bob Thanks for that, I've found the actual manual which is only 35 pages, not too bad.

The comment there about line contactors I find a bit confusing, it states:-

""In power control mode using a line contactor :

- Do not switch contactor KM1 frequently (otherwise premature aging of the filtering capacitors will occur) and use inputs LI1 to LI4 to control the speed controller.

- If the cycles are longer than 60 s these measures are absolutely necessary.""

KM1 is a line (supply input) contactor. I'm mystified as to why

*longer* cycles make switching with the logic inputs essential, I would have thought it would be *short* cycles which required it? Rob, any ideas?

Cheers Tim

here

> Only a couple of PDF pages so file should not be too big.

try

>

Tim

I fully agree with your assessment. However, I th USING A LINE CONTACTOR When controlling the power with an isolation line contactor, avoid frequently opening and closing the line contactor as this can cause premature failure of the filtering capacitors and precharge resistor. Use inputs LI1 to LI4 to start and stop the drive controller. Limit operations of the line contactor to less than once per minute.

Earlier you wrote that you were using a rotary converter upstream of the inverter and also that it was being powered from single phase? Does this mean you have two wire, 415v phase to phase going into the inverter and if so why not hook up the third phase into the inverter to share the current in the input rectifiers? Or is your converter a motor driven generator or indeed something else I have not thought of? Just curious as I try and keep abreast of all the different and perverse ways of running 3 phase kit from single phase sources.

Cheers

Bob

OK the first bit about frequency of cycles is probably a misunderstanding of what they mean, maybe their wording is a translation from the original French? More frequently that once per minute is almost certainly what they are trying to say is a no-no. That wouldn't be an issue in this particular case, but I'm in the middle of running an extra wire through for a logic on/off switch on the lathe panel to do it 'properly'.

My wording about my supply wasn't a translation from anything, but it's obviously also been misunderstood I'm using a 3-phase, 415V, rotary converter to give 3 phases into the inverter (from a single phase supply). The inverter gives the dual benefit of delivering properly matched phases to the motor from the 'improper' converter output, plus a ramped start for those cold winter mornings. Variable speed will be an useful bonus.

People do run 415V inverters from single phase stepup transformers but unless they're designed for single phase input they need to be substantially derated, I might need a 20hp drive to run my 10hp motor successfully that way.

Cheers Tim

here

>>> Only a couple of PDF pages so file should not be too big.

try

>>> HTH

Thanks Tim,

I understand now. I run a few small woodworking machines from single phase stepped up 230-415 but I'm rarely pushing them hard. Despite inverters seemingly monitoring so many parameters, I've yet to find one that checks for all input phases present - thankfully!

Cheers

Bob

There's something strange going on with this drive. First test on the lathe were done with keypad control, everything seemed fine. Then I found a grotty old 10K pot & wired it direct to the speed control terminals, it had no effect at all. I wasn't surprised because of the state of the pot, assumed it must be faulty. Now with it wired through to the original 1K pot on the lathe (yes, 1K is OK by the book), speed control still doesn't work. It was doing the right thing at the inverter control terminals (checked the voltages), but I could only control the speed by adjusting the 'min frequency' setting on the keypad. This drive is one I've had for 2 or 3 years, 'pre-owned', and doesn't owe me anything. I know I tested it when I got it, 99% sure I did that with a speed pot. Studied the book in case there might be something disabled, couldn't find anything, but found there's a way of adjusting the motor speed via the logic terminals, one for + speed & another for - speed. Lashed something together to give that a try, it only works (by the book) *up to the speed set on the pot*. Yes, that method works, but the odd thing is that having reached max speed by that method I can then reduce the speed using the pot, but not bring it back up again. BUT, if I leave 24V+ to the +speed logic input, I then get full control via the pot. To those who know a bit about these things:- (a) does this indicate there's a fault, or should I carry on looking for something wrong with the configuration? And (b) is it likely to harm anything if I leave the 'speed +' input permanently connected to 24V?

Tim

Tim, it sounds like the inputs are configured so that the analogue sets the maximum frequency instead of the running frequency; I would think an evening spent reading the manual may reveal the parameters needed to set it correctly! It never fails to amaze me how many parameters some inverters have to seemingly achieve the same result, in particular the Siemens units seem to have more than any other as John S alluded to. Martin

I am truthfully under the impression that inverter manufacturers are running a contest to see who can write the most obtuse handbook ever. I had words with IMO when they brought the current cub range out over a couple of matters. One was the book is printed on A 9 paper and even the guide dog can't read it and secondly again there is no simple setup for 3 wire operation.

They did agree on the second point and then brought a simple setup leaflet out that accompanies the new inverters but they still omitted the 3 wire operation.

Currently Siemens are leading, it's no wonder they bombed ower chippie in the last war if these inverters were fitted to the bomb bay doors...........

John S.

Yabbut who's going to buy an inverter that's got barely any features and will work without any more configuration than looking at the label inside the cover and setting a couple of DIP switches. It's obviously not what the market needs.

"How many times to we have to tell you people that there's no demand for those things? You're the fifth person who's asked this morning..."

Mark Rand RTFM

There were these

The instruction book is just 20 pages of A6, readable size print, but they've been replaced with the ACS55 which looks more 'conventional' though still described as 'simple to install', maybe the ACS50 really didn't sell?

I don't know how good the ACS50 would be in running machine tools, though.

Tim

Actually that's not quite true, when I was at Control Techniques, the drive I designed for them was a simple drive. It was open loop V/F or open loop vector control. The manual was dead simple, there were't many connections to it. Thet was Commander SE. The Commander SE replacement which has now been on the market for ages is a more complex beast, and in my view somewhat misses the point of a simple drive. You could say it was a posh motor starter.

To be fair, the build cost between a simple and more complex drive is bugger all, but the IP costs are greater. ie, you have to pay a software guy for longer to make the spec document a reality.

A lot of manufacturers miss out on the simple stuff, because they don't think the volumes are there. They probably are but you have to make it bloody cheap or you won't shift it.

Rob.