Here is a list of all the postings Rockingdodge has made in our forums. Click on a thread name to jump to the thread.
Thread: Lathe/VFD/DRO issue |
19/07/2023 11:44:16 |
Well, hopefully, a final update. The vfd is now in a cabinet along with the filkter kindly donated by Robert also fitted the donut, the cable is grounded to the cabinet and the 3 earths taken to one of the fixing bolts on the mounting plate and the filter is grounded as well. I have grounded the cable screen to the motor as well as it is a pain to access for the wiring so decided to do it all once and once only. The good news is that the dro display is now rock steady with the lathe running so many thanks for all the advice and support I've received, especially from Robert who went above and beyond. Regards Roger |
16/07/2023 11:39:08 |
Posted by not done it yet on 16/07/2023 08:31:39:
Any resolution to this thread? Soon be a month since started and seemingly no working fix. Or is the warning of not buying cheap (possibly sub-standard) kit, from the likes of vevor, the best advice - for all those reading this thread and considering purchasing similar kit? SOD, well said, Dave, in answer to your query it is just 10 days since the last post and in regard to my purchases and 'timely fixes' I'll just say this - I have no problems or issues with the quality of my purchases and have no issue in recommending them, when I bought my vfd to run my 1937 Denham lathe it did so with no issues. When I bought my dros' for my Warco mill they worked as expected and with the accuracy I expected, the only issue arose when I fitted my lathe with the same brand of dros, it happens! Robert and others in his profession are well paid (I hope) to plan/fix/avoid this very issue with, I assume, much more expensive and complicated equipment than we are likely to use so why do you point the finger at my purchases rather than accept that this kind of issue can happen? It is quite definite that my installation left a lot to be desired hence my reaching out to this forum and the experts within to help me understand and fix the issue. As to the length of time this thread has been running I do sincerely apologise but beg forgiveness as in this time I have also built a tool store according to SWMBOs requirements, battled with my own health issues as well as my wifes and done a number of trips helping my son to move house stuff into storage prior to their impending house move, as they say life always gets in the way but I promise to try and do better! Roger Edited By Rockingdodge on 16/07/2023 11:40:03 |
04/07/2023 10:14:33 |
Should I / can I bring the dro panel earth into the enclosure and earth it there as well? |
03/07/2023 17:33:45 |
Which end to earth, or both is much debated. The only printed advice I've seen was for double shielded wire, which suggested the inner be earthed at the noisy end, and the outer at both ends. I'd start by earthing only at the VFD end, and if that didn't fix the problem, both ends. Note that an earthed shield shouldn't be used as a safety earth. The safety earth has it's own wire, preferably inside the shield. If Robert RPI reads this, would Ferrites help? My feeling is not. Dave The one thing that confuses me is the difference between the safety earth and shielding earth, unless I'm supposed to ground the shield earth/s (there are 3 more in the main cable) to some other 'earth' other than the mains earth then surely earth is earth and thus the mains cable carries the difinitive earth? I'm old and confused |
Thread: Forum Platform Changes - PLEASE READ |
03/07/2023 15:14:35 |
I can remember, when working for a company that produced personalised 'fincial cards for various institutions, the unique file incrementing clocked over to 9 digits and the director from the Netherlands who was temporarily in charge issued the instruction to change the system to the current windows flexibility until I suggested that we did an impact analysis first as we had a number of piggybacked systems that adhered to dos file numbering systems, that was nearly the day that almost half of our manufactering lines would have crashed, oh happy days and long long hours. Roger |
Thread: Lathe/VFD/DRO issue |
03/07/2023 13:32:24 |
Now that I will have the necessary bits to 'hopefully' remove the interference from my vfd/motor/mains in cabling I just have a couple of queries:- Is it bad practise for the mains in and the vfd to motor cable to cross over or should I route the cables away from each other? Can I tie all the earths onto the mounting plate of the enclosure and then take one into the vfd? So the final question is - do I earth the screen earth both ends or not? Regards Roger |
03/07/2023 13:20:34 |
Update on the cable :- Inverterdrive got back to me at 9:45 am and agreed it's the wrong cable, seems their supplier sent the wrong reel and my cut was the first off! They are sending a replacement overnight for me, first rate service in my eyes. The filter from Robert arrived this morning with an included 'donut' as well so I'm praying for a stormy wet day so that I can argue for having a day in the workshop. Regards Roger |
01/07/2023 13:28:45 |
Just sent an email with a photo of the cable, I wait with interest to see what their reply is and how fast they reply! |
01/07/2023 13:08:12 |
As per Robert's request via pm this is the cable sent by Inverter Drive which we think is the wrong cable. Regards Roger |
27/06/2023 16:49:01 |
Today's (Monday) update:- Fitted cable with shield grounded to motor, results were mixed, am radio was still swamped with noise, the DRO readout did show improved stability at times, seemed to depend on where the crosslide was. Next stage is to order a box and fit an input suppressor unit (might as well as I need to rewire anyway) and see where that takes me. Robert Good idea on using a compression fitting as a gland/shield earth, worked a treat but had to cut the locknut down due to the curvature of the motor casing. Time to ask for a pocket money raise from the missus( that'll cost me a clothes shopping trip Roger |
25/06/2023 14:26:38 |
Posted by noel shelley on 25/06/2023 13:24:44:
Robert, with the material the spiral is made of being a chromed brass strip and each turn interlocked with the next and provided the 2 ends have continuity with the fittings please explain how or why it will not provide screening. Each turn of the spiral is part of the strip and any gaps between turns are tiny and the interlocking is such that there is no line of sight to the conductors. Noel. Noel, Thanks for the idea but I have ordered and received the correct inverter cable which will be fitted as soon as there is a wet day to stop me working outside so this discussion re shower hose is kind or irrelevant. But thank you anyway. Roger |
24/06/2023 18:26:01 |
Posted by Macolm on 24/06/2023 17:30:25:
Screened cable can be useful in managing emissions, but be aware that high frequencies can propagate through it as a coaxial mode. Unlike ventilation holes which work as short sections of cut-off waveguide which have a lower frequency transmission limit, coax has no lower cut off frequency. Thus it should be used to provide distance between the interference and the susceptible circuit.
If things need to be in close proximity, consider feed through capacitors, failing which any filter needs to be connected with as short wires as possible. This should be as near the interference source as possible. Sorry Malcom, That kinda went way over my head, I'm aware of capacitors in electronic circuits and motor start and run ones but saying I should consider feed through caps. means nothing to me without an explanation of how they're connected and what values would be needed, I'm assuming the filter you mentioned is one on the mains input side which we will look at if required. Is your paragraph about screened cable referring to my current cable, which seems to be the initial source of my interference or the cable which I will replace it with? Thanks for your input but please expand on it for a non-expert in this field. Roger |
24/06/2023 13:52:45 |
Posted by SillyOldDuffer on 22/06/2023 20:01:25:
Might help to listen to the VFD with a battery powered portable medium wave radio. Close to, VFDs emit a harsh roar covering most of the band in a series of broad peaks and troughs. The radio can reveal if interference is on the mains cabling, or on the motor cable, or the VFD, which helps target the problem. Sorry to be a Jeremiah, but it will probably be all of them.
Good luck, Dave Just checked with an am radio and the source does seem to be the output cable from the vfd so we'll see if it makes a difference when I change the cable. Roger |
24/06/2023 12:25:49 |
Just got the cable delivered from Inverter Drive, downside was the postage cost about the same as the cable If I were to go down the metal wall box route how do I go about cooling the vfd without comprising the shielding? Roger |
23/06/2023 12:52:33 |
Posted by John Haine on 23/06/2023 10:50:31:
Posted by SillyOldDuffer on 22/06/2023 20:01:25:
Posted by Rockingdodge on 22/06/2023 18:31:50:
Thanks Robert, Nick,
Good luck, Dave I love it! I'm lucky in that the pendant is removable so if I have to buy/build a box I an get a longer cable and mount it outside. Roger |
22/06/2023 19:44:23 |
Thanks Robert, And an input filter? Type, size, supplier? |
22/06/2023 18:31:50 |
Thanks Robert, Nick, But surely if I tie the 3 earths and the shield together isn't that a case of 3 potentially current carrying earths in with the shield? I'm sure I've read that somewhere but am probably wrong as usual. Will the 1.5mm2 be ok for a vfd of 2.2kw ? Roger |
22/06/2023 17:33:04 |
Posted by Robert Atkinson 2 on 22/06/2023 17:22:31:
I've been working all day so am just catching up. Mike and Nick have covered just about everything I would have suggested. Thos those saying gland plates will make no difference. This is plain wrong. 360 screening is well proven. Even with the same connector changing from a pigtail screen connection to flaring it out evenly over a ferrule and clamping under the cover make a huge difference, typcally at least 30dB (1000 times). This is part my professional field of expertise. EMI/EMC is part of my day job. I am currently involved in producing the next revision of the EMI/EMC standard for civil aircraft. I have significant practical experience, including on industrial type equipment. This includes design and testing. Robert. I am interested in what you say even though it's like skylab passing over my head and apologise if any of my previous posts upset you, that wasn't intended but some of us have to run our hobby on state pension and these days it doesn't go far at all, especially when the missus goes clothes shopping. I just need little cost effective steps to get to the point of having a workable solution please. Where would the 3 earths connect to in the motor? Roger |
22/06/2023 16:45:18 |
Posted by Nick Hughes on 22/06/2023 16:41:39:
For the VFD to Motor wiring, this is the type of cable that you need and the correct gland:- Also ask them to recommend which of there mains filters would be suitable for your VFD Thanks Nick but why do I need 3 earths? |
22/06/2023 15:47:14 |
Posted by Mike Poole on 22/06/2023 15:39:21:
Roger, the situation you have found yourself in is a perfect example of what can go wrong when an installation does not properly address the control of electrical emissions. Very often a noisy VFD will not be a problem until a piece of equipment that is sensitive to noise is operated in range of the noise source. You may have unwittingly brought a noisy VFD, a sensitive DRO and a wiring installation that does not meet the requirements to control emissions. Input and output filters are often omitted from drives to keep cost down but the filters are usually available as separate components. The incoming mains filter can help to reduce the noise fed back into the wiring system but emissions radiated from the drive can be usefully screened with a metal enclosure. The braid of an SY type cable is primarily a mechanical protection and other types of cable will have copper braid screen and maybe a copper foil layer in addition, CY is a cable with better electrical screening. The reason they make all this stuff and have recommended earthing strategies is because you are not the first to run in to trouble and I doubt the last. Much research has gone into the practical methods of emission control and it is worth following the recommendations. An industrial Ethernet installation in a car body welding shop has extensive earthing requirements and checking compliance was a part of the buy off process. Mains noise brought our factory to a halt for 15 hours and cost a lot of money, although we did not prove it conclusively we strongly suspected that a large VFD was the source of our problem. Mike Thanks for the explanation Mike I appreciate and understand what you are saying and also what others have said but that is not getting me any further forward, when I bought the cable from Inverter Drive it was for the vfd to motor connection, at that time I didn't know or planned to add DROs to the lathe. What I am trying very hard to get is advice on what size cable (only need 2 mtrs, and possibly from where) plus what size filter to get and from where? Roger |
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