Member postings for Robert Atkinson 2

SOD,
Using a plug without insulating sleeves on the live and neutral pins?

While this old style plug is considered OK if already fitted. they should not be re-used on other equipment or if the power cord is replaced.

I strongly recommend that any of this type of plug used in an electronics or engineering workshops are replaced. There is a chance of a wire off-cut or bit of swarf getting trapped beteen plug and socket, touching the un-sleeved pin and becoming live. It can then be touched as you reach to remove the plug or operate the switch on a switched socket resulting in a shock, possible injury or even death, Old plugs should be destroyed to preveent re-use.

Robert G8RPI.

Hang on a minute guys,

Steve,

You may have made control panels, but that does not mean you are correct. Before posting I specfically checked the manual for the VFD you fitted and it states it needs to be protected in an enclosure and that EMI filters may be required. Strain relief? ANY flexible cable that is accessible and connected to a termnal block should have a strain relief. These drives are COMPONENTS not finished products. They need to be properly integrated with approprate fused, isolators filters etc. Unless it is part of a fixed installation it has to comply with the EMC and Low Voltage Directives (Yes even if it is not for sale). From the companies you say you did work for the machines may have been fixed installations which have different requirements particuarly for EMI/EMC. I cannot believe companies like those would allow this type of VFD to be installed unless it was inside an enclosure or at least in an inaccessibled area e.g. behnd interlocked guards.
You say you fitted EMI filters when PLCs were used. This proves that VFDs need them (some are internal) to meet the EMC emissions limits. Just bcaus it's not interfering with your kit does not mean it is not affecting someone else. It takes specialist equipment to check that equipment meets the requirements, but it is a legal requirement to do so. I have the equipment required (HP and R&S spectrum analysers and assocated equipment) and know how to use them. I do travel a lot. Last year I travelled frequently to North America and the Middle East to witness or carry out EMI/EMC tests. I have designed and built equipment that included VFDs and Servo drives and was responsible for ther compliance to UK, EU and North American electrical, safety and EMI standards. There is a big difference between designing something and constructing something following the typical diagrams in the manual. When Rockwell automation introduced their 2nd generation Ultra Draive we were the first company to use it in the UK. The machine would not pass EMC tesing due to the drive. This was despite all the required filtering. Rockwell were struggling and paid my employer for me to consult with them and identify the problem with the drive and design a solution.
Buying the travel adaptor from Boots does not make it OK. There has been a bit of a clap down since the BS for travel adaptors was published but certainly before then the majority of adaptors sold by Boots were unsafe.
I don't fly model planes. I have all the toys I want including a fullly equipped electronics workshop, I'm certaily not envious of you Super 7. If you were showing others how to do it properly you should have showed the splash guard in place. Having to reach over the lathe to operate the controls or emergency stop is very poor practice too.

I am a Chartered Engineer and the our professional standards oblige me to make the user aware of any safety issue I identify. I have many years experience designing and working on electronic equipment, industrial and laboratory equipment, aircraft, and aircraft equipment with the odd diversion building and running the worlds fastest car.

1/ Emgee hvave you visited Steve's workshop and examined the installation? If not how do you know what he has done? Note that I have restricted my comments to issues that are clearly visible in the photos.

Where do you get the information that the OMRON VS Mini VFD is in a IP20 rated enclosure? The manual clearly lists it as "open chassis".
As for opening the cabinet to use the controls on the front of the VFD, this shows your ignorance of how these devices are desined to be used. The front panel controls are designed for set up and troubleshooting, not the primary means of operating the drive. They are not robust nough for frequent use.

Robert G8RPI

Compliant to what? the regulation when the house was built? That is likey to be decades go. I assume by "catching" you mean it will trip an RCD. That is OK for shocks and shorts to ground IF an RCD is fitted to the circuit.. This is hghly recommended but no obligitory for the majority of domestic premises in the UK.
Shorts to ground and gross overlods are not the only risk. Now that MCBs and RCDs are catching "conventional" faults it now arcing faults that are causing a lot of fires. A conventional MCB can't tell the difference between a normal 1kW load and a 1kW arc. New devices that will trip on arcs are available but are not mandated (yet). In any case it is bad practice to rely on protective devices protecting against poor design or installation.

Robert G8RPI.

Hi Len,
I'm lucky that my employer pays for my membership (Fellow of Royal Aeronautical Society) and registration fees. Last year I even got them to pay my EASA licence renewal because someone was lazy and ticked "licenced engineer" on a customer document. Last time (5 year renewal) they said that they didn't use my licence so would not pay.
I've come across commercil electricians who didn't ven know basic stuff like a capacitor across the mains causes a current to flow but no power too be dissipated. This was in connection with a motor drive EMI filter tripping a RCD put passing a insulation test.
some time lateer I picked up an electricians course text book at a car boot and was shocked at how much the basics wer dumbed down or jut plain wrong.

Robert G8RPI.

Do you know if it was working OK before you aquired it ?
IT sounds a lot like a worn out thrust bearing causing the worm gear to jam. One bearing typically takes more load than the other, pushing th armature one way and pulling the other.
Ideally get the worm drive disengaged and see how the motor runs then. Also try and separate the motor connections form any other circuitry.

Robert G8RPI.

That particular adaptor is illegal. part from quality I can tell from the picture that it's not wide enough. This means you can pluld one pin in with the othar hnging over the side. If the pin is in the live side there is a circuit through the load to the pin on the side maiking it live. so the lod does not work so you reach to check the adaptor, touch the exposed pin and get a shock, possibly fatal.
It is lgal to sell items in the UK with a 2 pin euro plug as long as they are class II (double insulated) AND are upplied with an approved adaptor that has a fuse, locks th 2 pin plug in place and needs a tool to open. Lke this:
http://www.farnell.com/datasheets/12709.pdf

BS 5733 is not directly relevent, travel adaptors are covered by BS 8546.
How do you know the adaptor in the picture is marked BS 5733?

Just because you can buy something dosen't mean it's safe or legal for a particular application. For example non-uk mains leads are use by companies making equipmeent for export. One compny I worked for got a PAT operative in over the weekend and he cut the plugs off 10 machines waiting to go to the USA and fitted 13A ones. He did not get paid!

Robert G8RI.

Edited By Robert Atkinson 2 on 17/07/2020 18:39:44

Edited By Robert Atkinson 2 on 17/07/2020 18:40:13

That is not an example of correct installaton To comply with good practice, the installation manual and current regulations the inverter drive needs to be in an enclosure and cables should have proper strain reliefs as a minmum. It should probably have EMI filters too . I alse note the use of an unsafe and illegal adaptor with a 2 pin european style plug in it on he lower power strip. Cut the two pin plug off, smash it and the adaptor and put a proper 13A plug with a 3 A or 5 A in it on the lead.
Having sockets, adaptors and leads directly behind the working area of the lathe is poor pracitce too, They can be contaminated by colant, dust or swarf or hit if something gets flung out of the chuck.
I know this may seem picky but having seen it I have a professional obligation to make you, and anyone who might use it as an example, aware of the issues. If you wish to carry on like that it's up to you.

Robert G8RPI.

Is this a genuine Metcal tip?

Last time I took one apart it used Litz wire. That was several years ago though. Has th bit been used? migh seem obvious but if it's not been used much it won't have oxidised much.

Robert G8RPI.

Hmm,
You are correct in your understang of the building regulations but the person just has to be competent (This can be through education, training, experience or other means). This is different from a Competent Person which implies a formal set of requiremens. For Part P competence a business or company is not required and even for a business it's not the business that detemines competence, but the notifying organistion. The best known is NICEIC. Some seem to have lower reqirements than others. Individuals within the company are determined to be competent (by the notifying organisation) and they can move this to another employer or use it personally (subject to employment terms of course). Non desiginated persions (I hesitate to call them incompetent ) can do work under the supervision of the competent one but the final inspection and testin must be done by a competent person. I know of no legal requirement to have a certain levl of insurance, but it's a good idea. Using a notifying organisation is not the only rout to compliance with bulding regs, anyone can do the work as long as they can convince the local building control that they are competent and or any inspections required by building control assure ompliance. Note that the inspections required could (will?) make this approach more costly than using a approved electrician.
My own area of competency (aviation) requires me to be competent to determine that a design is safe and meets the regulations, but does not have a firm set of requirements defining either. Being a Chartered Engineer is common but not essential and not enough on its on. I'm a CEng now but wasn't whn I first held a CAA or EASA design signatory. Competence is determined by the CAA in this case.

Robert G8RPI.

Yes that ^

Robert G8RPI.

SOD,
Where do you get " a Competent Person is required to have 2 Million pounds worth of Public Liability Insurance! " from? For elecrical work , you just have to be competent, no defined formal qualifications or level of training etc specified by the law. The problem is that notification of notifiable works has to be done through an organisation like NICEIC so they may have requirements.

Note that this discussion has been about doing work on your own domestic property, not doing commercal work or work for others.

Robert G8RPI.

When I looked into it a few years ago the requirements were down to your chosen organisation. One I looked at just needed you to take their "approved" training companies part P course and pass the test. The coure was 3 days, no entry requirement but the suggested that if you had not done any installation work before you should consider their 5 day basic course. Eight days from zero to Part P. The Part P course seemd to mostly be how to read the tables in the regs and use a specific (not Fluke) multi-function tester. Oh they were agents for that tester but I'm sure there was no pressure to buy one....

I did the same with gas 12 years ago when we moved in to this house. Gas had been taken out so I put in all new pipes etc. British Gas put in a new meter and a good (ex BG) Gas Safe appproved fitter made the final connections, testing and signed it off. He wanted to know how I knew to sleeve the wall penetrations and seal them at one side only, I just read the regulations (it stopps the pipes chafing on the wall, leaking into the cavt and building up until it reaches a light switch - boom.

Robert G8RPI.

The "vibration" is definatly caused by low currents flowin through the skin under light contact. This can be proven by diverting the current i.e. get someone else to make good contac wih an other conductive part of the item. I only happensat very low currents.
You can also get the senstation by lightly touching something grounded but not connected ot the mains when also in firmer contact with an AC source. Again the source may nt be obvious.
The best check is still with an AC millameter to ground.

I have frequenly seen issues with visitors to the UK from north America using laptops (class 1 grounded ones) on travel adaptors that have no ground connection. The power supplies have two capacitors to ground, one from live and the other from neutral. These form a 50:50 votage divider to the ground connection so if you measure thee voltage on eposed metal like the USB port you see about 110V AC. The current is very low because the capacitors are the sme value. If one capacitor fails open circuit the item will still work but if you remove the earth there will be over 200V at much higher current available.

The sis similar issue with VFD EMI filters including those built in. These are large enough that significat current can flow if the earth is disconnected. You should never rely on the mouning screws for earthing, always connect an earth wire. Larger drives will trip a domestic 30mA RCD even when operating normally.

On qualifications, I'm not an electrican but am a professional eletronics engineer (Chartered Engineer)and apart form my current work on aircraft systems I have ben responsible for safety and EMI/EMC approval for equipment the used servo drives that are electrically the same as VFDs. I was lso taught and carried out elecriacl installation work many years ago.

Robert G8RPI.

You can change a plug or do minor electrical work in your home with no requirement for training etc. Notifiable work and work in special locations (e.g. bathroooms) generally requires you to be part P registered. There is still no requirement for formal qualifications, just that you are "competent" . Registration requirements vary with organisation. But you don't HAVE to be registered, you can do it yourself, IF you can convince your local building control that you are competent AND pay for any inspections they want carried out. I've not tried this, but rumour has it that you are unlikely to be sucessful or it would cost more than using a register electrician.

The other thing you can do is agree in advance with a registered electrician how much work you can do yourself. a They then do the final connection, test and notification. This I have done, running SWA cable fitting mounting boxes etc and it saved a fair bit.

Robert G8RPI.

This just goes to show how one bit of bad information on the internet net propagted until it's the truth!

These are for setting small inclines or falls for drainss, trenches etc. NOTHING to do with parachutes. This example https://www.worthpoint.com/worthopedia/ww2-period-parachute-tester-1946447318

is clearly marked in inches per yard - inclination. The strong spring keeps the string ( running to a point higher or lower than the meter) tight and (mostly) straight. The arm the string runs through detects the angle of the string relative to the body which is levelled by the bubble.

What the heck would you test on a parachute with this!

Robert G8RPI.

It's one of those things you have to have felt to understand. With very low currents at mains frequency light contact wit a live part e.g. with the bak of your hand, produces a feeling more lie a vibration thna a shock. Often firm contact produes no shock or other sensation. It seems to be dome kind of physiological effect with the skin and maybe short hairs. A bit weird but well established.

Robert G8RPI.

Correct, but I did require a KNOWN erthed object, the screw was just an example. I'm sure someone would have complaind if I'd said to stick it in the earth hole of he socket , and that is not rellable unless you have a correct sized pin in it.

Robert G8RPI.

The above is incorrect and misinformed to put it nicely. You cannot possibly know if there is a problem with the OP's laptop / powersupply or not. Just because you were not electrocuted does not meant that your old laptop was OK either.

Don't give safety advice when you are not competent in the area.

Robert G8RPI

This tingle is caused by leakage current from the power adaptor. The leakage current is often caused by interference suppession components, as has been mentioned by others, in particualy a "Y" capacitor across the isolation barrier. This current should be less than 210 microamps (0.2 mA 0.0002 A). and not normally detctable.

My concern is that this is a used device so you don't know it's history and the AC adaptor may have been replace at some time, possibly by a "clone" that might not meet current safety standards. From the photo it doesn't look the 4 years old that date on the unit implies and used latopts often come with "new" power supplies. Ideally you dhould have it checked.

If you have a meter that reads AC milliamps you can do a quick check yourself. Place the laptop on an insulating surface (plastic cutting board is good), switch it on with mains power and connect the meter (set to AC milliamps) between a known earthed object (e.g head of the screw holding down the mains socket) and an exposed metallic pat of the laptop. The OUTER metallic part of a USB socket is good, but don't put the probe into the socket itself. Use proper test leads and don't touch any metal parts when doing the test. If you get a reading of more than 0.2mA stop using the charger and get professional advice.

Robert G8RPI.

4mm wide, but how long snd how thick? What is the bond area? That said a metal filled epoxy like JB weld, Araldite Steel is likely to be the best choice if you want a hidden bond as the glue line or fillet will look like steel. but from your described requirements any epoxy or super glue would work. For structural meatal bond toughned acrylic like Loctte 330 or Permabond TA435 are a good option.

Robert G8RPI