METAL DUST & VFDs

[noel shelleyParticipant @noelshelley55608]

Gentlemen, I have a 150mm wide linisher used for brass, which when in use leaves a fine coating of brass dust on things around the workshop. Would those with experience or knowledge of the potential risk that this dust would eventually short out a VFD care to comment on how to maintain cooling to the VFD yet stop metal particles entering and causing smoke to escape ? The motor will be a TEFC type. Noel.

[noel shelleyParticipant @noelshelley55608]

[Dave SParticipant @daves59043]

I would put it in a box with filtered forced air cooling.

doesn’t need to be fancy filters, just something to stop the brass – a panel filter for a car engine might be what I’d use as I have them available. Even a pair of tights from swmbo over a tube would work.

Dave

[AJWParticipant @ajw]

I know your problem! I have setup my VFD's fans to only operate when needed with temperature rise I also have a simple elasticated filter fitted around the body casing.

Alan

[Robert Atkinson 2Participant @robertatkinson2]

Any VFD should be in an enclosure.
Metalllic or carbon dust will cause failures if it gets into a VFD and could even cause a fire.
Check the requirements for your VFD the smaller ones taht we tend to use may not need forced air cooling of the enclosure if the enclosure is big enough.
If you do decide on forced ventillation of the enclosure , go for low velocity as this is less likely to pick up dust, A larger low volume fan is better than a small screamer. Have the fan blowing out of the case and have a filtered inlet area greater than the fan area. They sell filters to go on fans like this
https://uk.rs-online.com/web/p/fan-filters/7374099
These can be on the case away from the fan.

Would need data on VFD to be specific on size.

Robert G8RPI.

[Mark RandParticipant @markrand96270]

Just a shield will probably do the job.

Ideal solution is a bloody great dust extractor on the linisher.

[martin haysomParticipant @martinhaysom48469]

Posted by Mark Rand on 02/05/2022 12:28:18:

Ideal solution is a bloody great dust extractor on the linisher.

would keep it out of your lungs too

[EmgeeParticipant @emgee]

Posted by martin haysom on 02/05/2022 13:54:34:

Posted by Mark Rand on 02/05/2022 12:28:18:

Ideal solution is a bloody great dust extractor on the linisher.

would keep it out of your lungs too

Dust extraction is definitely the best solution.

Emgee

[ChrisBParticipant @chrisb35596]

Depends on what type of VFD you have, there are VFD's which do not require any dust protection because they are already protected from the factory but they all come at a price premium. These are IP54 and over, the most common type of VFD is IP20 rated and this will have no protection against dust and anything coming out of your grinder.

I have 50x2000mm belt grinder powered by an IP20 Invertek Optidrive E2 VFD, it's fairly expensive so I made a totally sealed enclosure for it. The enclosure is a pelicase in which I fit the VFD and it's controls. I took off the original case of the VFD then ducted the heatsink and sealed it from the out side so that there is no exchange of air to the case. The cooling air just flows through the heatsink.

Some might think the enclosure is too small and it will over heat, but in reality the enclosure plays no part in the cooling capacity of the VFD, the heatsink does. I operate the grinder in +35degC ambient temperatures.

Some photos of the setup which could be adopted to other types of VFDs.

The Invertek Optidrive E2 VFD as originally purchased

Pelicase enclosure – I transferred the original display to the enclosure and installed the controls.

The heatsink is ducted and totally enclosed, so the air flowing through does not enter the case, it just cross flows through the heatsink from one end to the other.

The VFD minus it's original cover.

The plug connections power in for the VFD and power out to the motor.

[Martin KyteParticipant @martinkyte99762]

As has been said it all depends on the device. If it is a unit that has a heat sink on the back and you can bolt the heat sink to a metal plate then you have a way of getting the heat out of the enclosure without the need for air cooling. A metal box with fins or an extended plate with added heatsink should be sufficient to create a heat path.

regards Martin

[Speedy Builder5Participant @speedybuilder5]

Why do you want to protect your VFD – you won't live to see the VFD die if the dust is as you say. First job is to put an extractor on the linisher !

Just as an example, my friend is a wood turner and has now a lung disease caused by dust from sanding an exotic wood piece on the lathe. Its so bad that he has had to give up wood work all together. Don't let the brass win.

Bob

[Mike PooleParticipant @mikepoole82104]

I would fit the VFD in an enclosure anyway, you may find that is does not run too hot and fans will be unnecessary. If it does get too warm then a fan extracting the air from the enclosure and a filter on the other end of the enclosure will keep the inside clean. Heat exchangers are available for control panels that keep the interior air separate from the outside air but they still need filter maintenance.

Mike

Edited By Mike Poole on 03/05/2022 10:41:49

[ChrisBParticipant @chrisb35596]

Posted by Speedy Builder5 on 02/05/2022 21:14:16:

Why do you want to protect your VFD – you won't live to see the VFD die if the dust is as you say. First job is to put an extractor on the linisher !

Bob

The OP's question regards the VFD, we can side track and discuss ohsa but it's not what he asked…maybe he does take care of all that. Personally on my machine I dont have dust extraction so I wear a full face mask. I don't want all the grinding dust all over my machines (which are vfd powered as well) so I grind in a small separate room.

Regarding cooling of the enclosure, if I had to put an cooling fan to it I think I'd rather make it to push filteted outside air in the enclosure rather than the other way round and extract air from the enclosure. If the fan is extracting air it's going to create a negative pressure inside the enclosure and out side unfiltered air will try to get inside from all crevices you might have even though there is a filtered inlet.

[John Doe 2Participant @johndoe2]

Can I just say, ChrisB, what a nice installation you have built there ! Good engineering to keep the heatsink cooling air completely separate from the electronics, and well done for lining up the front panel with the circuit board switches – that must have taken a couple of attempts.

And proof, if it were needed, that the front panel switches of a VFD are not designed for heavy use – you can see (the five yellow dots near the readout display); they are just tiny circuit board switches, not designed for heavy regular workshop use.

[jaCK HobsonParticipant @jackhobson50760]

I have had a vfd die and a couple stop working but come back to life after opening up and dusting with a brush.

I now have VFD in a large enclosure covered by a cloth.. .e,g, on a middle shelf with cloth pinned across the top and bottom shelf, or in a plastic box with cloth draped over it.. No problems since doing this. The forced air enclosure above is better and smaller and looks pro, but as a quick soln, simple works (I've been running like this for years).

[norm nortonParticipant @normnorton75434]

I have in the past left my VFDs out in the cool, and dirty, air and apparently this is wrong. I spoke to the chap at Transwave and for our small power requirements of one horsepower or so they can go into a sealed enclosure with no air cooling. The waste heat they produce is just a few watts; even tens of watts will dissipate from a metal enclosure.

Transwave said to me that a common cause of circuit board failure was from spiders who became 'fried' in their explorations.

Edited By norm norton on 03/05/2022 11:07:26

[norm nortonParticipant @normnorton75434]

Sorry, got my companies mixed up – last post should read Newton Tesla, not Transwave !

(edit facility vanished)

[Robert Atkinson 2Participant @robertatkinson2]

Just a note, IP54 only provides protection against limited amounts of dust. It is not generally adequate for electronics in a machine shop.
The fundamental issue is that almost all VFDs are components and need to be installed in accordance with the instructions. The instructions are intended for qualified competent persons. Virtually all VFDs need to be enclosed with proper protection, earthing cable strain relief etc etc.

Robert

G8RPI.

[RobCoxParticipant @robcox]

I have 2.2kW VFDs running both my M300 lathe and Omnimill. Both are in IP66 sealed metal boxes. The Teco unit for the lathe is mounted on the back of the lathe, the WEG unit is in a wall mounted box. Both VFDs have (approximately!) the specified clear air gap above and below to permit air circulation. All the on/off and fwd/rev controls are taken via the control interfaces to remote switches (the original lathe controls in that case).

These have been running for 5 years now and have never given any problems, even with fairly heavy use from time to time.

So to answer to OP's original request, stick the VFD in a large enough metal box with no vents and it'll be fine.

Rob

[ChrisBParticipant @chrisb35596]

Posted by Robert Atkinson 2 on 03/05/2022 12:45:16:

Just a note, IP54 only provides protection against limited amounts of dust. It is not generally adequate for electronics in a machine shop.
The fundamental issue is that almost all VFDs are components and need to be installed in accordance with the instructions. The instructions are intended for qualified competent persons. Virtually all VFDs need to be enclosed with proper protection, earthing cable strain relief etc etc.

Robert

G8RPI.

True IP54 is not totally dust proof, but it is more than adequate for a workshop setting. Limited protection against dust means that the amount of dust which can enter will not interfere with the correct operation of the device. If we take the Invertec VFD for example, the commissioning instructions recommend that an IP20 VFD is installed in a pollution degree 1 environment (ie a clean room/lab environment). If it is to be installed in a pollution degree 2 or higher a minimum IP54 enclosure is required – that is quoting the manual. So it all depends on your VFD and what it's rated for. There are even IP66 rated VFD's for outside use.

[Robert Atkinson 2Participant @robertatkinson2]

The IP 5x test uses nonconductive dust (talcum powder) so is not adequte to protect electrical equipmnt against conductive dust.

Yes you can get fully protected VFDs, at a cost. Most model engineers on here seem to use the cheap far eastern VFDs. On many of those wven the basic IP20 is dubious

Robert G8RPI.

[EmgeeParticipant @emgee]

Posted by Robert Atkinson 2 on 03/05/2022 16:25:46:

The IP 5x test uses nonconductive dust (talcum powder) so is not adequte to protect electrical equipmnt against conductive dust.

Yes you can get fully protected VFDs, at a cost. Most model engineers on here seem to use the cheap far eastern VFDs. On many of those wven the basic IP20 is dubious

Robert G8RPI.

Hobert

I believe the size of the particle is the deciding factor when conducting a test for ingress of dust, it matters not whether the particle is conductive or not.

How many of the cheap far eastern VFD's have you examined and tested to arrive at your conclusion of dubious ?

Emgee

[mgnbukParticipant @mgnbuk]

I believe the size of the particle is the deciding factor when conducting a test for ingress of dust, it matters not whether the particle is conductive or not.

From an "expensive bang" POV it matters quite a lot !

I work for a graphite machining company & the talcum powder fine stuff defies all attempts to totally keep it out of enclosures despite my best efforts – and that is IP66 industrial enclosures.

Nigel B.

[EmgeeParticipant @emgee]

Posted by mgnbuk on 03/05/2022 20:40:48:

I believe the size of the particle is the deciding factor when conducting a test for ingress of dust, it matters not whether the particle is conductive or not.

From an "expensive bang" POV it matters quite a lot !

I work for a graphite machining company & the talcum powder fine stuff defies all attempts to totally keep it out of enclosures despite my best efforts – and that is IP66 industrial enclosures.

Nigel B.

Sounds like the enclosure is not up to the specification, or the cable terminations don't have the same spec.
Perhaps in place of talcum powder the test house should be using graphite dust.
Your experience shows it is the particle size that's used in the test that matters, not whether it is conductive or not.

Emgee

[SillyOldDufferModerator @sillyoldduffer]

Posted by Emgee on 03/05/2022 22:38:04:

Posted by mgnbuk on 03/05/2022 20:40:48:

…

I work for a graphite machining company & the talcum powder fine stuff defies all attempts to totally keep it out of enclosures despite my best efforts – and that is IP66 industrial enclosures.

Nigel B.

Sounds like the enclosure is not up to the specification, …

Emgee

I suspect they might be – in the test, IP66 is only dust proof for 2 to 8 hours and not waterproof. Next level up (IP67) is only rated water immersion proof for 15 minutes.

IP66 should be good enough for most dusty environments, but resisting long-term heavy exposure to graphite fines is a tough requirement. The particles are both tiny and slippery.

I was surprised to find that many ordinary seals are actually rather leaky. For example, a cap-seal good enough to contain liquid paraffin slowly leaks vapour, and is nowhere near good enough to contain Hydrogen.

Dave

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