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Member postings for Robert Atkinson 2

Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Lathe query.
22/10/2021 11:55:23

Before you jump into electrics, can you turn the lathe by hand?

Either at the chuck or belt /motor. It the spindle is locked you will get an electrical overload. Mis-cordinated controls could lock the spindle.

Robert G8RPI.

Thread: Load reactors for VFDs
17/10/2021 20:34:06

Hi Andrew,

you said " The cost of the inductances are well nigh zero. I have a large amount of various diameter copper wire and stacks of iron E and I section for the cores. The only expense would probably be for the capacitors and I may well have some that would do the job "

For your concerns I don't think you need a full sinewave filter. Just some series inductance. There are two many unknowns with th old motor to make an optomised solution. As you have some suitable parts I suggest you just make up 3 identical inductors with what you have. A core 3 or 4 inches square and around 3" stack thickness would be a good starting point. For 1/3 HP 1mm dia (18SWG, 0.8mmsq) would be conservative for current and limit th turns enough that it's unlikely to saturate. Just fill the first bobbin with neat winding. Keep count of the turns and don't over fill the bobbin. Put the same number of turns and laminations in the other two.

This will be better than nothing and ony cost your time and the wire.
For leakage currents you just need a small carbon brush on a spring pressing on the end of the shaft. Obviously this is connected to ground. A brush of a small DC or universal motor wuld be OK.

Robert G8RPI.

16/10/2021 21:09:57

I agree with what Mark Rand said. I'd add a couple of comments / questions.

Are you using the the VFD to increase the speed of the motor? If you are this is more likely to stress the insulation in the motor. A VFD typically increases the output voltge with spped to maintain the current. If you are jut doing single to 3 phase with the VFD it is not an issue.

What VFD are you using? what does the manual say about load reactors?

While specific motor drive reactors are expensive, they are nothing special. Just 3 inductors of suitable value and current / voltage ratings. The value depends on the VFD PWM frequency. For just transient suppresion a lower value may be adequate.

Robert G8RPI.

Thread: Power Feed failure
12/10/2021 21:08:17


I can't tell if the auxiliary contact is Normally Open (NO) or Normally Closed (NC). This is the green terminals at the end. Can you check with a meter?
If they are NO (same as main contacts) this one will do the job:

The coil failure may just be random or the VFD waveform may have been the last straw. Either way replace the contactor and either wait and see if it is OK. Cheking the voltage across the coil.would be a good precaution.
Personally I'd wire the 110V transformer directly to the mans bypasing the VFD. The transformer may have a suitable 240V winding.

Robert G8RPI.

Edited By Robert Atkinson 2 on 12/10/2021 21:08:48

11/10/2021 20:14:54

If you are using the VFD to change the motor speed, rather than just single to 3 phase at a fixed 50 or 60Hz you will have problems. The VFD output voltage varies with the frequency (speed). This is to maintain the correct current through the motor. The issu is transformer ratios are fixed regardless of frequency. This means that the contactor coils may be overloaded depending on the exact design and settings.
Many VFD designs also generate high voltage spikes during operation. These can cause insulation breakdown in the contactor coils. These spikes and the waveforms enerated by the VFD also mean you cannot use a common multimeter to measure voltages.
To get accuracy you need a "True RMS" meter accurate to several kilohertz. To safety and to prevent damage to the meter it should be PROPERLY rated as CATIII 100V minimum.

You should re-wire the machine so the control circuits and power traverse are powered from a supply derived from the fixed frequency mains. The VFD shoud power the motor only.

Robert G8RPI.

Thread: HELP needed
09/10/2021 15:22:29

Fumes from hydrocloric acid will rust everthing in sight.

HCl has no place in a machine shop.
Also note you now need a locence for any significant strength of Sulphuric acid including battery strength. Technically emptying the acid from a battery to use as a pickle is a crminal offence.

Thread: Voltage sensitive relay
07/10/2021 17:58:25

You can feed the new fusebox from the AUX battery terminal on the VSR. You should fit a fuse rated to protect whatever size of cable you are using to feed the fuse box at the VSR end. Otherwie if the cable chafes it will cause a fire.

Robert G8RPI.

Thread: Chain Protection Sleeve
05/10/2021 19:48:39

I'm not so sure about the braded coverings. They are good on hoses and cable bundles, but there is nothing to stop the filament moring apart. I'd be concerned thet the corners of the links could spread the filaments enough to be exposed.
Maybe a hybrid of thin wall silicone tube and rided nylon would work.
The siliconised woven glassfibre tube products are intended mainly for temperature protection. Most are not great for abrasion resistance or even repeated flexing.

Robert G8RPI.

05/10/2021 15:58:15

Silicone rubber tube? This is fairly thick wall but might not be tough enough. Use soapy water as lubricant while fitting.

Robert G8RPI

Thread: Another what is it?
04/10/2021 12:20:51

A typical use is setting spring tension. You apply the force by hand to a position or stop dictated by the application. Another is to measure the tripping force of a sear or similar. There is a "tell-tale" pointer that stays at th maximum force reading.

Robert G8RPI.

Thread: What Material for this Application Please?
01/10/2021 08:53:32

Some of the imfamous plastic cored decorative building cladding comes to mind. Aluminium composite material (ACM) panels
Metal faced for durability but the platic core makes it stiff and "dead" so won't act like a wobble board and make a lot of noise in the wind.

If they are de-cladding a building near you it might even be free.

Robert G8RPI.

Thread: Scam? Definitely!
28/09/2021 17:34:31

same here in firefox or Edge

Thread: Multimeter recommendations
26/09/2021 20:13:22

SafeBloc was different brnd and design from Keynector.
Keynector looked, as the name implies, a bit like 3 piano keys, You flipped back an isolator at the rear, pressed the bak of the key and the frony opened.

The Safebloc had the isolator contacts in the flip-up lid. Under the lid were 3 more conventional metal clips, These are much further back from the edge of the cover than keynectors contacts. Thus safer with less chance of a stray live strand sticking out.
The Safebloc does not look as nice, but it is safer and you don't have to strip back as much of the outer sheath.

I have examples of both.

Robert G8RPI.

Edited By Robert Atkinson 2 on 26/09/2021 20:14:43

Thread: Heatshrink sleeving as a heat insulator for valve handles?
26/09/2021 15:56:34

ATUM of similar glue lined hestshrink is not a good idea as the glue will soften with heat.
Silicone rubber tube is a good option. The only issues are that it tends to be thick wall and most types have poor resistance to oil and grease.
If you want to try heatsink I'd suggest Raychem DR-25. This is a durable thick wall tube and will give reasonable insulation. As Calum points out it can loosen with time. The best solution for this is to use a thin layer of epoxy under the heatshrink. Try it without and if happy but it loosens replace it and use epoxy.

Robert G8RPI.

Thread: Multimeter recommendations
25/09/2021 17:27:51
Posted by Michael Gilligan on 23/09/2021 16:49:59:

Despite the ‘no longer available’ message … my local Aldi has these in stock at £9.99


Has any forum member tried one ?


Panel says "CAT III" and "300V max" which is impossible. Probably not safe for use on mains and counterfiet CE marking.

Robert G8RPI.

13/09/2021 08:15:14

Hi Nick,

That is fine. As long as it is just your personal use and you have assesd the risk and accepted it. This is like so many other things in ME which would never be allowed in a commercial or industrial setting.
I'm not trying to be the "safety police" . I just want people to have correct information so they can make that informed judgement. There ais a lot of poor information oout there. Regulations and guidance also evolve and what was "OK" last year may not be today.
For anyone using meters in any kind of commecial or public environment they really should be fully compliant. As Trevor says you might just hve to answer for your actions. Also if you have insurance they may quibble about it and not pay you or try to claim back off you for a 3rd party payment..

Thank you for your comments. On CE marks, the one on SOD's "830" meter is incorrect but it might be an old meter. Those shown by others appear to be the correct mark but unless the item is fully compliant they are not valid.
Interestingly. if you want to sell into China they do not accept CE UL etc. You have to submit samples and full technical details to a test house in China and pay for testing. Somone cynical might say that clones would be on the market before you approval was granted.....

Robert G8RPI.

12/09/2021 22:43:03

Well both CPC and Farnell list Tenma for that model number but that supplied to you and pictured on their websites is branded "STANDARD" The claim on the website is they meet IEC1010 (no dash number or date specified IEC1010-2 is for centrifuges) not EN61010. The IEC 1010 standard is obsolete and is replaced by EN 61010-1. (the latest version of 61010-1 also requires compliance with parts of EN61010-2-30, another document to buy).

You could ask CPC for evidence of the meters compliance, but they are just taking the suppliers word for it. Am almost tempted to buy one and challenge it. CPC sell "retail" so I could go to Trading Standards.

The slightly more expensive Duartool DO3144 loks better at lest it quotes 61010-1 band the manual specifies 600V 10kA breaking fuses, but the tepmerature / HFE input is not protected to 600V (manual page 4 f says 250V. ) So that is also a clear failure.

There is a reason why compliant meters cost more. Caveat Emptor and if it looks too good to be true it probably isn't.

B.T.W. checking compliance of aircraft parts is part of my day job. A few years ago I found that ta safety compliance test of a electrical component had not been done correctly in two respects. The test intention is actually similar to part of EN 61010-1. This was an exsiting part and thouands are fitted to airliners.The part maker agreed that the test had been done incorrectly and neither the approved independant test house, the part maker or the aircraft mnufacturer had noticed! They re-ran the test, but did it wrong again! The got it right on the second re-test. Fortunatly the part passed or there would have been a huge re-call required. The tests cost in the 5 digit range.

Robert G8RPI.

12/09/2021 19:49:42
Posted by SillyOldDuffer on 12/09/2021 16:55:36:

Posted by Robert Atkinson 2 on 11/09/2021 13:00:40:

From IEC 61010-1

"16.2 Multifunction meters and similar equipment
Multifunction meters and similar equipment shall not cause a HAZARD in any possible combination
of RATED input voltages, and settings of function and range controls. Possible HAZARDS include
electric shock, fire, arcing and explosion.
Conformity is checked by the following test.The maximum RATED voltage specified for any function is applied to each pair of TERMINALS in
turn, in every combination of function and range controls. The test source connected to the
equipment measuring TERMINALS during this test is limited to 3.6 kVA for measurement category I
or measurement category II. For measurement category III or measurement category IV, the test
circuit has to be capable of delivering 30 kVA.

During and after the tests, no HAZARD shall arise.
Multifunction meters and similar equipment are to be tested by changing the Functi
on/ /Range Selector to all
possible settings while connected to the maximum rated source.”

Robert G8RPI.

Excellent to see what IEC 61010-1 actually says! I think it can be read two ways, one of which is Robert's strict interpretation, the other much less onerous. As Devil's Advocate:

First, the successful test is one in which there is no HAZARD. I argue this means it doesn't matter what happens inside the case provided the explosion, fire and arc are contained and can't physically harm or shock the operator. A hand grenade could be safely exploded inside a sufficiently strong box. The contents would be completely wrecked, and the box bulged, but I claim it's a pass.

Secondly, what's meant by 'The maximum RATED voltage specified for any function is applied to each pair of TERMINALS in turn, in every combination of function and range controls.'? I could argue it doesn't mean 600VAC must be applied to all the terminals and switch settings. For example, my less rigorous interpretation is that the maximum RATED voltage on the 200mV DC range function is only 200mV, not 600VAC. Not difficult.

Thirdly, the input energy of a CAT I or CAT II test is limited to 3.5KVA, which is far less than a sand-filled mains fuse has to cope with. Even if the meter disintegrates inside the box, 3.5kVA isn't spectacular unless the current continues to flow. I argue there's no particular reason why it should, and in practice all those thin PCB tracks will break almost instantly. It's another pass.

Just a hypothesis. Though I suggest an overloaded M-830 would still fail safely, with minimum HAZARD, I don't know! However, if my sophistries are correct, it might explain why weedy multimeters are CE marked and equally acceptable for sale in the USA and all other administrations around the world. They can't all be fakes can they? Maybe IEC 61010-1 isn't that demanding, or perhaps all the testers have been bamboozled by smart lawyers!



PS. I actually sympathise with Robert's line on electrical safety: in practice I'm pretty careful with volts and amps.

Hi Dave I think it is clear that it is the maximum CAT rated voltage that has to be applied. Thus if a unit is CATII 600V even if the equipment specification says 500V max, the test applies 600V. Also the same voltage is applied to all termin combinations on all switch settings. This is common sense as there is nothing to stop the operator setting up for current measurement and then connecting between live and neutral instead of live and load. In safety terms this is a "slip" and has to be expected.
The hazard of arcing includes internal arcing. If this was not the case Fluke etc would not use expensive fuses designed to contain the intentional arc of them fusing. An uncontained arc can lead to other hazards.
No "830" meter is really safe for use on the mains.

Robert G8RPI.

12/09/2021 19:34:55
Posted by Nicholas Farr on 12/09/2021 13:35:37:

Hi Robert, for your information, this is the card that was in the packet that my new multimeter came in, which claims it's conformance of EN61010-1 CAT III. All I can do is accept what it says.


Regards Nick.

Edited By Nicholas Farr on 12/09/2021 13:44:31

Hi Nick, I assume that paperwork came with t "STANDARD" ST913 in your earlier picture. If that is the case I can say it is incorrect just from your picture. Theis is because there is no CAT rating next to the input terminals.

Additionally the paperwork does not reference a model number and the make of the meter in the picture does not ppear to be STANDARD. If you read the link I posted earlier there are ots of meters that dont meet the declared CAT standard. Did the suppliers catalog or web listing actually state it was CAT III 600V?

Likewise your UNI-T UT61 is non compliant because the rating has only been appled to the Volts/ Ohms terminals. A meter has to pass on ALL inputs and functions to be compliant. Current ranges are harder than voltage to make compliant.

Manufacturers and suppliers make all sorts of incorrect or plain fradulent claims.

Robert G8RPI

Thread: Help identifying some tools
11/09/2021 13:06:18

The Bundenburg dead weight tester should have a matching set of weights. normally thes are paired to the tester. Unfortunatly they often go missing...
With the weights it has some value.

Robert G8RPI.

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