VFD tripping RCD

[Jan-DIY]

Just a note to type B RCB.
B is also sensitive on DC current which is often generated by SMPS.
If type A kicks out, type B will also do so.
Danfoss drives 28series got the filter as an option. Afaik it can be cut out by removing a screw.
Regulations says that unfiltered devices are only allowed in industrial environments. Forbidden in commercial because it maybe generated high EMI noise which can harm other devices.

 

[hermetic]

Thanks brightspark, just bought one! Although I am retired now it is nice to know yer gear is right!
Phil

 

[brightspark]

i have a seaward checkbox 16 it tests earh loop. rcd .continuity resistance. insulation resistance and voltage measurment .paid 80 quid second hand for it of ebay

 

[Beanwood]

Thanks all - there's a LOT to think about.

as above current imbalance. disconecting the earth will make the frame go live and dangerous if its sat on anything insulated it will run ok sit it on anything metalic thats earthed and it will trip and if your in circuit between earth and case and you will fry

I think I'm finally starting to understand RCD now - but if it works by calculating the difference between live and neutral, then won't it still work, even with no earth ? Good old wikiperdia seems to think it should work?

It will work but if there is no path to ground any conductive parts will sit at mains voltage, you will get a shock. The RCD will never trip and the only protection you have is the fuse and MCB, which will trip long after you are gone.

An isolation transformer before the VFD would also defeat the RCD and prevent tripping, but at the same time make it somewhat safer as the metal parts would still be safely earthed. Relatively large and expensive though.

So, if I ground the frame directly, just not through the RCD, presumably it would still trip out if there's an issue?
However I like the idea of an isolating transformer - I suppose I'd need to calculate what Kva I need, then see what's available

I used input suppression on my dual vfd setup at work. I found it tripped just turning them both on.

Schaffner 10A, 250 V ac Flange Mount IEC Inlet Filter FN9264-10-06, Faston | RS

uk.rs-online.com

View attachment 346525

I don't know if this was aimed at solving my problem, but for under £20 if it would work for me (By presumably stopping the DC current leak to earth) that looks good doesn't it?

Beanwood, it may be that there ia a leakage on the machine itself, has it been stored for a time before you got it? megger testing the machine with the VFD disconnected would find this out. You could have a particularly "dirty" supply which presents a lot of transients at you incomimng mains, in which case a surge protector fitted to your incoming supply immediately before the RCD may cure the problem, but not without cost, so I would get the machine tested for leakage first.
Phil

Exactly....get the motor checked out....everything else is work round and not ideal. Damp is often the cause. My Elliot shaper has an antique 240vac motor and that doesn't cause trip outs either. Neither does any of my other equipment. The shredder after it was left out in the rain did and ended up at the tip. The electric hotplate did in the caravan due to damp...dried out with blowlamp then ok.

It was still tripping out with the motor disconnected, so any problem will be with the VFD itself.

I don't think it's damp - but don't have a megger to test with.
All of my electronics knowledge is 40+years ago at college (Where embarassingly I did electrical engineering). Unfortunately it seems I've forgotten it all ecept V=IW ... oh and always keep your left hand in your trouser pocket when inspecting electrical installations.
If I end up testing for earth faults, I'll probably just get a sparky in for an hour or so.

Just a note to type B RCB.
B is also sensitive on DC current which is often generated by SMPS.
If type A kicks out, type B will also do so.
Danfoss drives 28series got the filter as an option. Afaik it can be cut out by removing a screw.
Regulations says that unfiltered devices are only allowed in industrial environments. Forbidden in commercial because it maybe generated high EMI noise which can harm other devices.

Thanks - the filter is only optional on the larger VLT 28xx series - so I'm stuck with it.

 

[Seadog]

Unfortunately it seems I've forgotten it all ecept V=IW

You're right, you have forgotten it, apart from your left hand, that is

 

[Beanwood]

You're right, you have forgotten it, apart from your left hand, that is

Lol - OK - fair cop - I won't correct the equation above even though it's WRONG. (W=VI for anyone who's wondering).
I only remember that one as I use it regularly for aadding spotlights to cars and bikes over the years....

 

[Seadog]

Ohm's Law is one of the few formulae that I've committed to memory, that I use regularly, and I knew that from around the age of 8, long before I studied electronics at college. Another is the colour code.

 

[Beanwood]

Ohm's Law is one of the few formulae that I've committed to memory, that I use regularly, and I knew that from around the age of 8, long before I studied electronics at college. Another is the colour code.

BBROYGBVGW ?

 

[My Old Landy]

I don't know if this was aimed at solving my problem, but for under £20 if it would work for me (By presumably stopping the DC current leak to earth) that looks good doesn't it?

Hi, sorry it was aimed at the chap who had tripping from multiple vfd's in simultaneous operation. The filter I linked is for EMI suppression. It will remove transient spikes but I feel your issue is more linked to an earth leakage problem. If I was closer I could test your lathe and vfd but I am in Lincs

 

[Kram]

Any pictures of your setup? Motor wiring too.

I think the motor can be ruled out, the vfd will not be sending any power until its told to spin.

Try it at a neighbours/mates house and see if it trips with their RCD.

Instant tripping is suspicious, Id open it up and check all internal connections. One could have came off in post. Leave it without power for an hour, so there is no charge in the capacitors before you open it.

If you did try with a non earthed cable, and with great care (one hand in pocket, glove on the other, insulated tools, insulated surface) measure the voltage of the ground cable to ground.

 

[Beanwood]

If you did try with a non earthed cable, and with great care (one hand in pocket, glove on the other, insulated tools, insulated surface) measure the voltage of the ground cable to ground.

Thanks chaps - you've saved me from a nasty shock at best.
82.1V AC from the earth point to ring min earth point.
Time for a new VFD?

 

[hermetic]

time to get your mains checked by the supplier for excess transients, or that faulty capacitor in the array that is dumping unbalanced chage to earth! Can you get another filter for the VFD or fit a non genuine replacement filter?, if it is not a faulty filter a new VFD will not cure the problem

 

[Beanwood]

time to get your mains checked by the supplier for excess transients, or that faulty capacitor in the array that is dumping unbalanced chage to earth! Can you get another filter for the VFD or fit a non genuine replacement filter?, if it is not a faulty filter a new VFD will not cure the problem

Thanks Phil, not for the first time on this thread, I'm confused. Isn't the filter/capacitor array within the VFD? (THis is a small self contained VFD, nothing external). I measured the 82V from the VFD earth point (i.e. on th VFD frame) with mains being connected to it, not set to start, and without the motor connected (So I'm fairly confident the motor would be OK.)

My thinking is keep it safe, and just replace with something such as @hotponyshoes posted earlier:

VEVOR VEVOR VFD 1.5KW Variable Frequency Drive 7A 220V Single Phase to 3 Phase Inverter Converter for Spindle Motor Speed Control | VEVOR UK

Discover VEVOR VFD 1.5KW Variable Frequency Drive 7A 220V Single Phase to 3 Phase Inverter Converter for Spindle Motor Speed Control, Premium Quality and Powerful Performance at lowest price, 2days delivery, 30days returns.

www.vevor.co.uk

 

[Kram]

That does indicate a fault in the vfd, but might be usable as is. First it needs to be opened up and checked as it may also be a fire risk or a very easy fix - 30ma is 7.2w, 300ma is 72w - a lot of extra heat, likely on a tiny component.

Ground the motor and machine, making that safe. Stick the vfd inside an earthed metal enclosure (good practise, protects from dust and moisture), but do not earth vfd, use an insulating spacer to mount the vfd. Wire controls on the front ensuring good insulation for all switches and wiring.
Use a screened motor cable, but screen only ground at one end, either to motor or enclosure, not to vfd.

I dont mind checking vfd over if you post it here and back.

 

[prepman]

Thanks Phil, not for the first time on this thread, I'm confused. Isn't the filter/capacitor array within the VFD? (THis is a small self contained VFD, nothing external). I measured the 82V from the VFD earth point (i.e. on th VFD frame) with mains being connected to it, not set to start, and without the motor connected (So I'm fairly confident the motor would be OK.)

My thinking is keep it safe, and just replace with something such as @hotponyshoes posted earlier:

VEVOR VEVOR VFD 1.5KW Variable Frequency Drive 7A 220V Single Phase to 3 Phase Inverter Converter for Spindle Motor Speed Control | VEVOR UK

Discover VEVOR VFD 1.5KW Variable Frequency Drive 7A 220V Single Phase to 3 Phase Inverter Converter for Spindle Motor Speed Control, Premium Quality and Powerful Performance at lowest price, 2days delivery, 30days returns.

www.vevor.co.uk

Your home and dry....plenty of cheap VFDs out there...all mine are AT1s generic Chinese. However I suspect they're programmed to stop working if we attack China...

 

[Anguz]

Back off and blow it out with an airline before you spend any money

 

[Beanwood]

Back off and blow it out with an airline before you spend any money

That's not a bad idea thanks @Anguz

I dont mind checking vfd over if you post it here and back.

@Kram that's very kind of you. Let me check on postage costs and take it from there. (No point in throwing good money after bad and all that).

 

[Beanwood]

That does indicate a fault in the vfd, but might be usable as is. First it needs to be opened up and checked as it may also be a fire risk or a very easy fix - 30ma is 7.2w, 300ma is 72w - a lot of extra heat, likely on a tiny component.


I dont mind checking vfd over if you post it here and back.

OK - so 7 months down the line, this finally made it's way to the top of my 'fun to do' list, and I bought a new VFD.
If you'd like the old one - it's yours for the cost of postage.

 

[prepman]

OK - so 7 months down the line, this finally made it's way to the top of my 'fun to do' list, and I bought a new VFD.
If you'd like the old one - it's yours for the cost of postage.

And.....it all works? Please tell.
Going back to the thread beginnings about RCDs. I was taught (60s) that live and return neutral were bifolar wound coils, that is to say 2 coils wound in opposite directions which negate their magnetic fields any leakage from either circuit (to earth) causes and imbalance. This pulls the trip mechanism.
Most sensitive I've used if I remember correctly is 10mA which is rated for personal protection.
So anything <35mA was deemed safe. Continentals were using these, while we were still on the old rusty nail.

 

[Kram]

OK - so 7 months down the line, this finally made it's way to the top of my 'fun to do' list, and I bought a new VFD.
If you'd like the old one - it's yours for the cost of postage.

Thanks, I dont have a use for, space or really, any time for another project. You said it does appear to be working apart from the leakage so should be a relatively easy fix for somone.