vfd inverter for Myford

After reading the discussion here about vfd and filters, I wonder whether one from a scrap washing machine might fit the bill there are plenty around or are they just a luxury we don't actually need or require.. John

Re EMC filters, There is a legal requirement for them - the EMC Directive.

Steviegtr:

We are talking DOMESTIC installations not industrial the EMC requirements are very different. See link posted by Old Mart https://inverterdrive.com/group/AC-Inverter-Drives-230V/Schneider-Altivar-12-ATV12H037M2/
The fouth paragraph states (for the 1C1 VFD)

EMC Filters to EN61800-3 to the 1st Environment C1 (Domestic) for cable lengths up to 5m.
EMC Filters to EN61800-3 to the 2nd Environment C2 (Industrial) for cable lengths up to 10m.

The higher emissions for industrtral applications mean that longer cables (which act as antennas) can be used with the same filter. From your post and others you have made I believe you were mostly involved in fixed plant sytems that have even less requirements.
Apt from that, if someone else designed the panels you were buliding how do you know there were no filters? The designer may have chosen VFDs with built in filters.

There is a requirement for putting the VFD in a suitable enclosure - The Low Voltage Directive.
Again refering to the earlier link, the line beloe forth paragraph says " Cubicle mount. " VFDs are components, not finished products. The guides and manual on the linked page say " Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. " Thes units do not have the level of protection required (touch proof terminals, robust terminal covers, cable strain relief etc) to be afe if not mounted in an enclosure. ltion for full EMC compliance is 1 to two days work in a specialist facility costing around £5000 per day. No I'm not suggesting a hobby installtion should do this, but at least do the basics and use a filter.
Not interfering with one DAB radio does not mean the installtion is not causing harmfull interference elsewere. Thesting a VFD instal
You can do whatever you like in your workshop, but plese do not encorage others not to follow good advice.

Clive Brown 1.

The fact that your drive tripped the MCB means it was not suitable for the domestic installation. Disconnectin the filters is not a cure. The correct solution to this would be to run the machines off a separate supply with a less sensitive RCD. Alternatively you could use a filter with less "Y" capacitiance but this will normally be more expensive as it typically needs more or larger inductors. You also have to make sure it is effective. Just because the drive manufacturer provides a means to bypass the filter, does not mean you don't need a filter. Typically the drives with filters have passed EMC testing (in a very controlled configuration) and if the installer wishes they can use this to assume compliance in their installation (they are still responsible if it does not comply). If you do not use the supplied filter you have to assume the unit is NOT compliant and take other measures such as your own filters.

I have done this and acheived full EMC and electrical safety compliance for small machines with multiple drives. It's not always easy. Our main drive suppler brought out a new family of drives (existing ones to become obsolete). We were the first users of the new drives. When we tested a machine with the new drives fitted it failled emissions totally. This was not even a power issue were the normal filters are but on control lines that we needed. Turns out they didn't connect all the control lines when they did their compliance testing. I designed a low level signal filter tht solved it on our inital production and helped the OEM re-design the drive circuit for a proper fix. As a result we got a lifetime special discount on those drives tha added up to a lot of money over the years.

Again, I don't suggest that hobby installations need to show full compliance (legally they do but enforcment is very very low) but we should follow good enginerring practice and use these things in a safe manner. While it is extremely unlikely to happen, if there is an accident (might not be to you if it's caused by EMC) or your house burns down because of a poor installation you could end up on the wrong end of a lawsuit or denied insurance claim. It's not happened yet, lets not be the first.

Robert G8RPI

Mains borne interference caused a £1,000,000 breakdown in our plant, my colleagues and I worked all night and finally concluded the supply was our problem, we resupplied the machine from a clean supply and it was smiles all round. In the post-mortem the finger was pointed at the large VFD units on the building roof for the space heating system. The investigation by a mains condition specialist did not find the smoking gun but the company threw some money at the job and the machines critical parts were supplied from some Emerson UPS mains conditioning units which solved all its troubles. The problem had shown itself a few times over the space of a couple of years but disappeared as quickly as it had occurred. The system finally became so unstable that production was abandoned and our brief was to work all night to try and find the cause. A car body in white shop is an electrical noise nightmare, hundreds of robots all with inverter drives and hundreds of inverter weld controllers are a recipe for mains borne trouble, a faulty filter is all it might take to cause mayhem on mains sensitive equipment.

Mike

Edited By Mike Poole on 23/11/2020 14:07:56

More doom and gloom from Robert.

Firstly why do manufacturers produce VFD's with control switches on the front panel and provide an IP rating that conforms with use in a home workshop environment without further protection. ?
Clearly because it is a self contained motor starter with speed control.

Provided the VFD is CE marked it has already been certified by the manufacturer to comply with the Low Voltage Regulations.

If users wish for their own reasons to mount the VFD in an enclosure and add a remote control station that is their choice.

Emgee

With regards to EMC which some VFD's have and others don't, the Sneider Altivar which I bought has EMC which can be disabled if required. As the mill is in a museum, I chose to keep the EMC enabled, just in case there were any legal requirements. Having EMC enabled does result in a measurable earth leakage, but I was relieved to find that it was not enough to trip the RCD protected supply. As the EMC is intended to reduce RF interference, in association with proper shielded cabling, there is a small risk of causing local problems with Wifi, tv's, radio, phones, and maybe heart pacemakers, and doorbells.

The self contained programming makes sense when you understand that the vast majority of VFD's are set up for automatic machinery, and left untouched. Anyone thinking that they could stop a machine in an emergency using the tiny stop button on the VFD as easily as hitting a full sized and correctly positioned emergency stop button is sadly lacking in common sense.

Using the controls from a scrap washing machine has possibilities, but the system is designed to be used with the original motor, and might not be compatible with other motors.

Edited By old mart on 23/11/2020 15:15:56

Edited By old mart on 23/11/2020 15:21:11

Firstly why do manufacturers produce VFD's with control switches on the front panel

To aid comissioning.

and provide an IP rating that conforms with use in a home workshop environment without further protection. ?

Inverters are usually IP20 - effectively little more than finger insertion proof. They are designed to be installed in a suitably protective enclosure.

Clearly because it is a self contained motor starter with speed control.

Nope. They are a system component.

Provided the VFD is CE marked it has already been certified by the manufacturer to comply with the Low Voltage Regulations.

Inverters are not CE marked - they are components to be built into a system & then the whole system checked for conformity.

If users wish for their own reasons to mount the VFD in an enclosure and add a remote control station that is their choice.

If all else fails - read the manual that accompanied the device. I have not come across an inverter yet that doesn't require fitting in a suitable enclosure. If you choose to ignore the manufacturer installation requirements that is your choice - maybe best, though, not to push that as best practice.

Nigel B.

Start here to find out more about installation, nothing there about enclosures.

**LINK**

Check the rest of the manufacturers information if you have the time.

Emgee

Although the VFD inside my lathe is reasonably well protected, it's enclosure is insufficient in that the terminals can touched accidentality and swarf could get through the cooling vents. Although fitted with a front panel that does all an operator needs, the panel isn't intended for grubby fingers on a regular basis. It's purpose is configure and test the VFD during set-up and maintenance.

I can't speak for all VFDs but mine, like the similarly protected contactor, is clearly a component meant to be mounted inside a box and wired to switches and a pot safely separated from the user. All the cheaper and mid-range VFD's I've looked at were components too, not meant to be used in an open workshop.

As botched home electrics go, I wouldn't put a cheap VFD top of my list. Better safe than sorry in my view though especially if the workshop has visitors. How difficult would be for an inquisitive child to poke terminals with a little finger?

John asked about Washing Machine Filters. Unlikely to be all that effective but should help a bit and wouldn't do any harm provided the one used can take the amps. I've thought of trying it.

I can confirm comments about the inadequacy of domestic radios to detect RFI. DAB and FM both have strong signal characteristics - they're deaf to anything less powerful than the station they're tuned too, and also only listen in the VHF range. An old AM radio is  better, but testing EMC really demands the right equipment.

Picture below is a slice of medium wave with the VFD on, but the motor off. The centre spike with fluffy sidebands in the lower pane is a local AM radio station, happily straddled by two powerful VFD noise peaks (one inside the green box.) These can only be found by tuning the radio to them.

Driving the motor makes the interference much worse, effectively zapping the whole medium wave:

Due to equipment limitations the images only show interference over a tiny part of the radio spectrum. Checking further shows my VFD puts out serious noise spikes all the way from about 25Hz to 150MHz. Not asked my neighbours if they have internet problems when I'm in the workshop, but ...

Dave

PS. After capturing the images I reduced the problem somewhat by fitting a shielded cable between motor and VFD. It's far from fixed though. I'd sort it properly if I used my lathe more often, only used it for less than an hour in the last week, so its unlikely to be a major nuisance. I hope!

Edited By SillyOldDuffer on 23/11/2020 17:38:02

The Inverter Drive Supermarket quick start guides always stress the importance of shielding. I used shielded wiring for the VFD to motor, the potentiometer and the remote emergency stop switch, and the steel box containing the inverter is earthed, including its door.

seems clear that it should be in a enclosure or electrical area.

Mike

Check the rest of the manufacturers information if you have the time.

Siemens manual for Sinamics V20 inverter

Section 3 Mechanical installatiion, Sub section 3.1 Mounting Orientation & clearance :

"The inverter must be mounted in an enclosed electrical operating area or a control cabinet"

Seems quite clear to me ?

Section 5 Commissioning via the built in Basic Operator Panel seems to confirm that the BOP is primarily a commissioning tool.

Nigel B.

(sorry about the font change - cut & paste from the .pdf changed it and I can't see how to change it back).

Edited By mgnbuk on 23/11/2020 19:51:49

Emgee,

It's not "doom and gloom" it's sensible advice from a professional. I see others have responded to your comments so I won't say more about that.

As I've said before what you do in your workshop is your business, but when anyone suggests doing something dangerous and/or illegal to others or states that good guidance is wrong I have a moral (and professional) obligation to make comment.

One thing I will add is the the manuals for VFDs assume, and normally state, that the installation design and work is carried out by a suitably qualified and experienced person (SQEP). I happen to be a SQEP for both the design and installation of VFDs and similar, you do not appear to be.

Doing installations in work or public areas like "Mens Sheds" and museums is a bit different. These normally have public liability insurance and it is worth looking at the "small print" they may have conditions limiting who can do things like electrical work.

Robert G8RPI.

Robert

Unlike you I don't shout it from the rooftop but I am a SQEP to design and carry out electrical installation and maintenance but now happily retired after running my own electrical installation and maintenance business for 34 years.
I gather from your comments over time you are electronically orientated and have very limited knowledge of electrical installations.

Emgee

A query if I might.

In the discussion on VFDs the subject of EMC filters is regularly raised.

As one who prefers not to interfere with others I am quite happy to fit one BUT I have yet to see any comment on what type of filter is required ( there are EMC filters and there are EMC filters ). It needs to meet both legal requirements ( if any ) and to do the job it is there to do.

If it is the small metal encased type costing a few dollars ( or pounds ) I am quite happy to fit them whether needed or not. However if it is the massive type costing a great deal more than a high quality ( i.e. expensive ) VFD then I need to know that the expense can be justified ( i.e. is there really a problem that needs fixing ).

Any advice from the suitably qualified - by training or experience - would be welcomed.

On the subject of enclosures - a good idea even if the VFD is located some distance from the machine. It is amazing just how far swarf will travel, especially aluminium, and where it will end up. Quite a few CFDs have an inbuilt fan which will draw air ( and light swarf ) into the internals with possible sad results. An enclosure will also provide protection against the odd flying missile - broken tool, chuck key etc.

Pero

Omron Mini J7 Installation notes.

Installation Direction and Dimensions

Install the Inverter under the following conditions.

• Ambient temperature for operation (panel-mounting): -10°C to 50°C

• Humidity: 95% or less (no condensation)

Install the Inverter in a clean location free from oil mist and dust. Alternatively,

install it in a totally enclosed panel that is completely protected from floating

dust.

If the Inverter is installed in an enclosed environment such as a box, use a

cooling fan or air conditioner to maintain the internal air temperature below

50°C. The life of the built-in electrolytic capacitors of the Inverter is prolonged

by maintaining the internal air temperature as low as possible

The J7 Inverter meets the EC Directives and UL/cUL standard requirements

for worldwide use. Directives EMC Directive EN50081-2 and EN5008-2

Low-Voltage Directive, prEN50178 ,UL/cUL UL508C.

Installing a Noise Filter on the Power Supply Side.

The Inverter’s outputs uses high-speed switching, so noise may be

transmitted from the Inverter to the power line and adversely effect other

devices in the vicinity. If this causes interference then, it is recommended that a Noise Filter be

installed at the Power Supply to minimize noise transmission. Noise will also be reduced from

the power line to the Inverter.

I cut & pasted this from The Omron inverter manual. I never said you could not use a enclosure or a filter.

The point i was making is that there is no Law that requires it.

Also an EX now retired Electrical contractor of over 50 years in industry.

Steve.

Edited By Steviegtr on 24/11/2020 15:34:29

Anybody can use the VFD for home use without any extra switch gear,or covering, if they want to. I had to at least pay lip service to health and safety with the one I installed at the museum for obvious reasons.

Omron J7 manual

The manual above says this WRT mounting :

Be sure the Inverter is protected from the following conditions.

• Extreme cold and heat. Use only within the specified ambient tem-perature range:−10 to 50 °C (14 to 122 °F) for IP20 (open chassis type),−10 to 40 °C (14 to 105 °F) for NEMA 1 (TYPE 1)

• Rain and moisture

• Oil sprays and splashes

• Salt spray

• Direct sunlight (Avoid using outdoors.)

• Corrosive gases (e.g., sulfurized gas) or liquids

• Dust or metallic particles in the air

• Physical shock or vibration• Magnetic noise (Examples: Welding machines, power devices, etc.)

• High humidity

• Radioactive substances• Combustibles, such as thinner or solvents

In the specifications section of the manual the device is described as "open chassis" - which is described as IP20 above. I don't see how the environmental requirements described above can be met with an IP20 device without enclosing it ?

Nigel B.

There lies the rub, a VFD is not electrical installation, it is electronic equipment / system design.

To properly and legally install a VFD of the type we are discussing (other than in an industrial "fixed installation" (which has a specific meaning) the finished product MUST comply with the relevant direcives (CE or in UK from 1st Jan 2021 UKCA) This as a minimum includes the Low Voltage Directive and the EMC Directive and in many cases the Machinery Directive. The electrical installation and BS 7671 ends at the socket on the wall.
Yes I'm primarlly electronics (avionics to be precise) but I have done domestic and light industrial installation work and a lot of equipment design and manufacture.
Came across this at work recently. Had a mains motor in a box with a solid state relay. The non-aircraft electrical people said "we have done it to "edition 18" I questioned this, but becuase I'm avionics (person involved did not know my background) they asked an outside certification expert - who confirmed exactly what I said - LVD and EMC Directive. They even chose the same harmonised standards I had.
The very fact that you don't think this is required shows you are not a SQEP.

Just because lots of people don't comply and enforcement is virtually non-existent does not make it right.

Very good question.

Practically you use the filter included with the VFD or that recommended by the maker of the drive. Even this is not certain to comply, in theory you have measure the emissions (conducted and radiated) from the equipment over the applicable frequenct range (typically 200kHz to 1GHz). and ensure it is below the limit.
As you might expect very few people do this for a single installation.

If he VFD supplier does not provide a filter or suggest a suitable one you have to use professional judgement, the rating of the drive and other information to choose a likely filter and then you have to test it with your equipment.

Robrt G8RPI.

Edit

Steve.

Edited By Steviegtr on 24/11/2020 18:05:52