VFD & Inverter questions

I was just wondering if the moderators of this site would consider an information channel of sorts. Please do not think I am trying to tell you how to run a brilliant forum, because this I am not.

It would seem a lot of forum members new & old, are fitting 3 phase inverters to there machinery. Most of the members are not electrically proficient & have difficulty when setting up this kind of equipment. Some do not even know if they have the correct type of motor fitted to do this. I have noticed when someone asks for advice that there are lots of answers given that totally confuse the question. Then some members clearly go onto google etc & copy & paste a lot of garbled nonsense that confuses matters more.

Things like oh you need a filter , but this will cost more than your inverter. Do not fit this as you will cause a nuclear explosion. (slightly exaggerated)

There are many inverters on the market. Some quality ones costing over £400 . Also lots of Chinese & other Asian imports that are in the ball park figure of the hobby enthusiast in the way of cost. Most hobby members will buy the cheap units as it is maybe in there budget. The expensive units have a lot of settings which are out of the reach of the average person trying to set one up. Some members of this forum are very good in that they know exactly what settings are what. But some just end up confusing the question to a point where the poor chap ends up having a breakdown.

I would not call it begginers question but maybe some thread they could look at instead of posting a question with a hundred incorrect answers.

Regards & stay safe everyone.

Steve.

The best information channel for inverters is the instruction manual for that particular inverter - they are not all the same.

Clearly some of them require extensive prior reading around the subject to make sense to the programmer (or sufficient knowledge of which parts of the programming is appropriate to their particular use of the product).

If the person who buys it is not competent to fit it the best advise is to get someone (who does) to install it and/or show them how to do it.

The usual is, however, to ask on a forum such as this where lots of people will try to help - often the blind leading the blind. It is then down to the OP to sort out the wheat from the chaff, the facts from the fallacies.

Of my four working inverters, none are identical. Even the two which look to be very similar are programmed subtlety differently. The other two I have used were different again.

So, in a nutshell, most of those that require help with an inverter installation would not be helped by a comprehensive document covering a multitude of models.

Picking up on NDIYs instruction manual and ease of installation points a simple report covering :-

1) what are you using it on

2) make, model and date of purchase

3) cost

4) how easy the instruction manual was to follow

5) how easy was it to connect and mount the device (some have very little room for the wires and tucked away fixing holes that is almost impossible to get a screwdriver straight onto the screw head)

6) did it work straight out of the box

7) if not, how easy was it to get the parameters right

8) optional advanced user comments on doing more than just basic run the machine set-up

9) if you had problems how helpful was the supplier

8) likes, dislikes and "the little issue that drove / drives you nuts"

9) bottom line are you happy wih how well it works and would you buy another

10) comments such as why you chose that one et al

would probably be helpful in making the appropriate choice.

Probably best organised as a topic folder with threads for each inverter model covered so folk could chime in with assistance on anything tricky. Needs to be strongly moderated of course.

Maybe supplier rating too.

The combination of technological advances and low cost of Far East imports means that most normal folk have no feel for the price / performance ratio of these boxes. As we generally need to make every £ do the work of 5 (or even 10) its awfully tempting to try and buy a little too far down market. When you do that all the trimmings that make life easy are the first to go.

For the size of device we are likely to use the price differential between inexpensive but not "too cheap to trust" import "no name" VFD boxes from "never heard of them" suppliers and a branded one from folk like Inverter Drive Supermarket is in the weekly shop or two territory. So it's getting hard to justify buying unbranded from a box shifter. Better to save up for a bit longer than risk being frustrated by making an inappropriate choice.

With a well chosen modern device installation isn't a problem.

The last two I installed were an Eaton DE1 and a Schneider-Altivar-ATV12.

The Eaton is designed to be a near direct replacement for a standard contactor and was pretty much as easy to install. Ideal for running my car lift. Just press the start button and it goes. Small enough to fit in the main box too. Just add switches (and a potentiometer if you want more than a fixed speed or two). But it doesn't have a display so you need a calibrated dial if using speed control.

The Schneider was effectively just as easy. No need for switches this time if you run it off the front panel but but it did need running down a simple set up choice menu including one to do its vector setting thing. The easy set-up manual on the Eaton was sufficient, the Schneider manual is good and easy to follow but Inverter Drive Supermarket have their own uber-easy "just follow the steps" version. Hafta say the IDS set-up manual was actually too easy for a guy like me with some experience. Started thinking about things instead of just doing it and had to start over!

Clive

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Edited By Clive Foster on 25/03/2020 10:30:01

I'm 100% with steve above, why not just help some one in need. I have three different makes of inverters, all pre owned as the car salesman says, and have received some helpful setting up advice here, I'm pleased to say. John

A very useful internet resource I've found for VFD info. is the Inverter Drive Supermarket website. They sell a fairly wide range of VFD brands, and for some of these they publish a downloadable Quick Start Guide, as well as the manufacturer's manual. The QSGs are written, I think, by IDS themselves and give very clear details of how to wire and programme for various remote control configurations, eg 2-wire, 3-wire, speed pot.

I don't think they cover the low-cost ebay offering though.

The forum is good in that it allows questions to be asked and answers given.

But we live in a imperfect world. Questions often leave out important facts, muddle terminology, or make incorrect assumptions. I don't suppose anyone deliberately gives misleading answers, but it's easy to get the wrong end of the stick, miss clues, indulge a hobby horse, repeat hearsay, be out-of-date, misremember, or misunderstand.

As the questions are technical, it should be no surprise that answers might be difficult, likely calling on specialist knowledge few of us have. Quite a few questions are answered early on, but the answer goes right over the forum's collective head, leading to further discussion and blurring. Or the answer is rejected because it doesn't align with pre-conceptions!

Personally, I think it's a mistake to expect the forum to provide simple answers to often difficult questions that everyone can understand. Although experts often take the time and trouble to help beginners through problems with explanations, diagrams and photos, normally threads have to be read carefully to separate the wheat from the chaff. I find considerable value in doing this because mistakes are as illuminating as good answers.

Two ways of making Stevies suggestion work occur to me:

1. Someone qualified edits finished threads to remove noise, check facts and explain.
2. Someone qualified writes a piece on a well-defined subject and has it peer reviewed before publication on something very like Wikipedia. (i.e Model Engineers take on maintenance of Model Engineering know-how. )

The problem is one of organisation and doing lots of hard work. If Stevie researches and writes his first draft of 'VFD's Made Easy', I'd can correct grammar, spelling, and spot clunky bits, but someone smart would be needed to explain what all the parameters are for. Probably a small team if it addresses different types of motor, safety, and selection criteria. Could be No 48 in the Workshop Practice Series...

Any volunteers? (I'm too busy!)

Dave

SoD makes excellent points about the difficulty of providing good, simple, advice on technical issues through a forum.

Especially because of the "multiple guru" problem where several folk with decent expertise say pretty much the same thing in different ways.

Ideally its best to not only stick with one guru but also to choose one who explains things in a way that suits the way you think. I'm sure everyone has had the experience of having something clearly and correctly explained to you but for some reason not being able to properly follow it until another person uses just the right form of words to break the logjam. Whereup everything falls into place and you feel really stupid for not getting it first time round.

However with the current, and future, state of the art sorting tricky technical questions after a VFD has been bought is probably not a good way to help folk. Far better to ensure they choose an appropriate one in the first place.

For the non-demanding applications that we will generally be concerned with there is a goodly choice of VFD boxes that really are easy to set up with straight forward step by step instructions that any methodical person can follow. As easy set up pretty much boils down do how well and carefully the control software has been written there is, unsurprisingly, no significant price premium for being easy.

As I suggested previously some sort of guide, in standardised style, from practical experience should enable a prospective user to see where a particular VFD sits on the easy set-up / installation techie level spectrum. Hence the purchaser can choose a drive they can handle. Even if problems are encountered the forum will mostly be dealing with only a subset of the VFD market concentrated around ones that are intended to be easy.

Clive

Hooray! People are recommending the Inverter Drive Supermarket. Their Quick Start Guides for some of the huge number of products they sell make diy a doddle even for the average buyer. Their prices are not that more than the ebay prices, but you do get real brand names and backup if required. The Schneider Altivar I bought was easy to wire with remote controls and easy to program. The easy start guide only covers the most useful programming features and leaves out the huge number of obscure parameters which are only of interest to very advanced professional users.

Of course the large number of people who ignore this will always bring a regular whining number of threads on the difficulty of getting VFD's to work.

Newton Tesla sell a package of inverter and control panel pre wired and set up for a range of popular lathes. I've bought 3 inverters off him, always had good after sales.

The manuals tend to be very hard going, mine are better than the ones for Chinese DRO, but not by much!

I think too many people buy an inverter, attach a power cable and a motor and switch on, after a battle with the parameters the job is regarded as finished. Newton Tesla provide a ready to go package which is put together properly by the looks of things and is oven ready, just bolt the bits on your machine. The inverter is one component of a drive and the rest of the shopping list should have an enclosure, some control items and some properly specified cable, filters and a brake resistor may be required. An ideal installation will not be screwing the inverter to the wall.

Mike

Another vote for Inverter Drive Supermarket. When I was converting my Chipmaster a few years back. Colin Gibson was very patient in answering my very basic questions and ensuring that I got the right spec product and associated components. This I was very grateful for and somewhat surprising for a commercial organisation who were only going to get a single order from me. On the back of this, the VFD (Emerson Commander) was installed, configured and worked first time. I will say that I did read the manual end to end before starting the install.

Their Quick Start Guides for some of the huge number of products they sell make diy a doddle even for the average buyer.

Unfortunately, one has to remember, by definition half the buyers are less than the average in the category. They may be wiz at machining to 1/2 a micron or some other attribute.

There will still be a large segment who simply buy the cheapest they feel will do the job. A proportion of those will be in the below average section of ability (in the programming category) - to read instructions and follow guides successfully.

There will be exceptions where the instruction guides are sub-standard, too - and many (otherwise competent) persons are likely to find programming challenging.

If instructions included a “quick guide to getting started”, it may help. One of my inverters had instructions for not only usual + or - 50 Hz operation, but also for high frequency drives. Until separated, the programming parameters listed could easily override the required outcome. Mine was basically configured for the high frequency uses.🙂.

Just looked on Inverter Drive Supermarket and Schneider 0.75kw is under £100 that's a lot cheaper than I was expecting, must have a look at Newton Teslar as well.

The only thing I found odd about the Schneider Altivar 0.75Kw (1 hp motor) was in the full manual, it called for wire sizes which would not have fitted the terminals. All of the cabling I used for power was 1.5mm and I crimped sleeves on them. The signal cables were much thinner, but all of the cables I used were shielded.

I have a large Boxford CNC lathe. The spindle is driven by a massive DC motor.

The motor is showing its age, and I am looking at upgrade options.

One option is to replace it with an AC motor and VFD - but I have no experience with VFDs.

I have 3 phase power available, so would only need the drive for speed control.

My question please - what range of viable motor speeds can I expect through a VFD please? What are your experiences?

For the technical I would probably use a 4 pole 2hp motor.

Many thanks

John

Manofkent, go on the "inverter drive supermarket" and look at the three phase motors, they usually have the speed and power output at various frequencies. I found that the 1hp six pole motor I chose worked well from 25 to 75 Hz. The power output drops off quickly with lower frequencies. I also bought a 0.75 Kw Scneider Altivar from them which was so easy to set up using their quick start guide. The whole setup cost me about £350, for 1hp.

Thanks Old Mart.

So I looked at some suitable drives on the inverter drive supermarket (that's a great resource by the way - thanks).

A suitable Parker drive says it varies down to 0.5hz which would in theory be about 70 rpm. Is it right to assume the motor power would be pretty well degraded at that level?. I guess there would be other issues such as heat.

Has anyone run a motor at 200 rpm ish from a VFD? , and if so how was it.

Thanks

John

I just lookedat a 1.5hp two pole motor and for the TEC brand, the rpm/frequency/power figures are listed.**LINK**

Tricky to give a simple answer, because much depends on the motor, the VFD and what it's used for.

Motor torque is degraded at low frequencies (and high ones), but the effect may not matter much. Modern VFD's apply techniques to increase torque at low frequencies, for example by altering the waveform to pass more amps - they aren't limited to sine-waves like the mains. However, the motor is likely to get hot, worse when it's only cooled by an impeller, and run very slow for a long time.

My Chinese lathe addresses the problem with a moderately clever VFD and a two-speed belt drive. It covers 30 rpm to 2500rpm in two ranges, which allows the motor to spin at a reasonable lick even at 30rpm. From memeory the belts are 12:1, so 30rpm at the spindle has the motor doing 360rpm. The motor is fitted with a separate fan that runs continually at high-speed and I've never managed to get the motor warm! I'm genteel hobby lathe work, with plenty of gaps between cuts, not a busy professional workshop working at top speed. Which describes you best?

Depends on the motor too. Provided the insulation can take it, the heat cause by slow speeds may not matter. Pre-war electric insulation may produce dreaded magic smoke at 80°C, later motors are good for 130°c or more, maybe as high as 220°C in this century. Heavily built motors dispose of heat faster than flimsy ones, taking longer to overheat. Fitting a giant motor to over-drive a machine tool is daft in my opinion, but could be sensible if the purpose is controlling heat at low tick over. Far better to fit a belt or gears to a suitably powerful motor though.

Dave

If you watch one of my video's i show various frequencies & the effects. Skip to 7.00 minutes for that part.

Myford lathe mods

Steve.