PAT testing Three Phase

[v2cola]

How do you PAT test a Three Phase applience?

 

e.g. CM LoadStar, motor controller

 

my IEE standards book tells me that..... "In some cases an adapter can be made by wiring all three pahses and the neutral (where applicable) together" ....... but this sounds wrong to me?

 

Does anyone know if you can even test three phase? let alone make an adapter from 32amp to 13amp to do the test?

 

I'm still learning so tell me if I'm being thick! :(

 

V2cola

 

[Colin]

When I test such things I use a 32A 1ph -> 32A 3ph jumper, in the 3ph end all phases are connected. This is not overly dangerous (if you ignore potential loading issues etc). I would then have a 13A -> 32A jumper and plug it into the tester.

 

A more scary concept is when testing things like 125A 3ph cable and you make the jumper 125A-> IEC.

 

DONT make a 3ph -> 1ph adapter by connecting all the phases for hopefully obvious reasons!

[Dmills]

When I test such things I use a 32A 1ph -> 32A 3ph jumper, in the 3ph end all phases are connected.

 

Works in the general case where the three phase feed is getting broken down, but is a pretty nasty thing to do to a three phase motor, especially if the star point is connected to neutral....

I would not go here for testing something like a three phase chain motor.

 

Personally I tend to test this stuff with an installation tester and a set of probes rather then trying to use a PAT rig which is clearly the wrong tool for the job.

 

Regards, Dan.

[v2cola]

Thanks Colin that makes sense, from my experience (seeing splitters and multicore black & melted) I get the fact you should never put 3ph into 1ph ..... unless making the other end of a cable tester to go in the IEC of a 1ph PAT tester. (only sending 1ph through the cable)

 

on the loadstars they have 4 pin 16amp 3ph (havent got one to check at home but sure there is no neutral) to make an adampter 13A 1ph -> 16A 3ph do you just leave the netural empty, wire the pahses together and earth to earth?

 

Thanks

V2cola

 

A concurrent post has been automatically merged from this point on.

 

Ok Dan, I don't know much about Star and Delta wiring but get what you mean as I've heard a verlide when it dropes a phase and it just went eeeeerrrrrrrrnnnnnrrrrrrreeeerrrrr and didn't work. sort of holding the armature in one place. could I test one phase at a time with three different plugs or a three way switch? :(

 

Thanks

V2cola

[c33kay]

How do you PAT test a Three Phase applience?

I was asked this question recently.. and didn't know either!

 

Personally I tend to test this stuff with an installation tester and a set of probes rather then trying to use a PAT rig which is clearly the wrong tool for the job.

So would you test each phase against neutral? I see how this would test the Earth leakage and insulation to Earth... but how would you check the insulation between phases?

[Dmills]

Personally I tend to test this stuff with an installation tester and a set of probes rather then trying to use a PAT rig which is clearly the wrong tool for the job.

 

Yep, and probably against the other phases as well, if it is a cable or similar (Not really appropriate for final loads however)..

 

I tend to take the view that the IMPORTANT bit of all this is the visual inspection not the faffing about with meters, as my experience has tended to be that the vast majority of serious faults get found by a good visual inspection before the kit gets anywhere near the test gear. The test gear is good for finding that 0.6 ohm earth bond on an otherwise functional computer monitor, but for things that actually matter, the visual tends to be the thing.

 

Regards, Dan.

[Andrew C]

I tend to take the view that the IMPORTANT bit of all this is the visual inspection not the faffing about with meters, as my experience has tended to be that the vast majority of serious faults get found by a good visual inspection

250-300 tests over the week end, and only one fail on the meter. I suppose we have 6-12 items that "failed" on visual, even if it was repaired immediately and re-tested. The one meter fail, is a pinspot that doesn't seem to have any form of earth, need to look at it tomorrow!

[Megahertz]

On most PAT testing machines, the live and neutral are connected together during the insulation test. Therefore, an adaptor needs to have the 3 phases (and neutral if there is one) all connected together at the socket, and then wired to the neutral on the 13A plug which goes into the PAT tester.

 

The live in the plug is not connected to anything - this avoids danger if the adaptor was accidently plugged into a socket.

 

If you are testing cables, you need to consider what MIGHT go wrong. The previous advice on visual inspections is spot on. If there was a short between conductors in the cable, this could be discovered with a multimeter, but it is difficult to imagine how this would occur without some damage to the cable which could not be seen by looking! There is however, a chance that one of the conductors could be broken - if the earth was broken that would make for danger. As a result a high current earth bond test should be carried out (probably at 26A) with a pass value related to the CSA of the cable and the length. If one of the other connectors was broken, that would be inconvenient, but not dangerous, so would not necessarily be picked up on the PAT test.

 

Most people would carry out a PAT test (for safety) followed by a function test to check operation.

 

A previous poster referred to the Earth Leakage / Load test - these cannot be carried out by a PAT testing machine on a 3 phase appliance. In any case they are not really necessary - the CoP requires a full inspection followed by an Earth Test (on a class 1 appliance) and some sort of test to establish the integrity of the insulation. In most cases the insulation test fulfils this requirement, although sometimes a leakage / touch current test is carried out as an alternative. Some people (erroneously) carry out all the tests as a routine.

 

Hope this helps!

[KevinE]

I really wouldn't try and test any 3-phase equipment with a standard 13A portable appliance tester, preferring to use individual instruments which any electrician qualified to test 3-phase stuff will have anyhow. Certain makes and models can have a retro-fitted special adapter, you have to perform the test manually and it only checks phases to earth insulation and earth bond test.

 

A pdf is available to registered users of Seaward pat testers detailing suitable test methods.

[Simon Lewis]

I really wouldn't try and test any 3-phase equipment with a standard 13A portable appliance tester

 

Well said... I know the boundary between "portable appliance" and "heavy duty piece of industrial machinery" can be a little blurred at times, but seeing as the IEE COP concentrates on 13A plugs, I wouldn't have considered portable appliance testing to be the best test method for such equipment.

[grizzly]

... but seeing as the IEE COP concentrates on 13A plugs, I wouldn't have considered portable appliance testing to be the best test method for such equipment.

 

Well...

 

IEE CoP for In-Service Inspection & Testing of Electrical Equipment (3rd edition), page 47:

10.2.1 Three-phase equipment

If the equipment is fitted with a plug complying with BS EN 60309: Plugs, socket-outlets and couplers for industrial purposes a three-phase/single-phase conversion lead can be made up and employed to enable a standard PAT to be used. Such special leads must be kept under the control of the test operative. Alternatively, an insulation/continuity test instrument can be used (see Sections 15.4 and 15.5), testing at the equipment terminals once the supply has been isolated and proved dead.

 

Seems the IEE CoP is pretty clear on the matter.

 

A concurrent post has been automatically merged from this point on.

 

I really wouldn't try and test any 3-phase equipment with a standard 13A portable appliance tester, preferring to use individual instruments which any electrician qualified to test 3-phase stuff will have anyhow. Certain makes and models can have a retro-fitted special adapter...

 

You can make up a 3-phase to single-phase test adaptor lead to use with any PAT instrument (as Megahertz outlines above)

 

you have to perform the test manually

 

Depends on the PAT instrument you're using. On some, you can program your own test sequence (see link below for example)

 

and it only checks phases to earth insulation and earth bond test.

 

Which is all that is really required of the PAT instrument in this instance. A functional test (not supplied by the PAT, obv) would highlight any other insulation issues. See IEE CoP page 73, section 15.3

 

A pdf is available to registered users of Seaward pat testers detailing suitable test methods.

 

Is this the document you mean: Seaward 2060 - Three phase testing?

 

It seems to agree with what I, Megahertz and the IEE CoP have to say on the matter. :)

[Simon Lewis]

Well...

 

IEE CoP for In-Service Inspection & Testing of Electrical Equipment (3rd edition), page 47:

10.2.1 Three-phase equipment

 

Seems the IEE CoP is pretty clear on the matter.

 

OK... I have COP edition 1 and 2 - where that isn't stated! Looks like I have to fork out for a new book again! However, the text you include suggests using other test equipment. Naturally, the competent tester will be comfortable with either making up and using cable adaptors or using test equipment that would normally be used for fixed installation testing.

 

I'd suggest that there are many people (perhaps even those who have passed the 2377 course*) whose knowledge is sufficient for basic testing, but does not extend to three phase systems etc. I suspect that for many places, keeping basic appliance testing to devices that have a 13A plug (or a simple adaptation such as 13A to 15A) is a convenient demarcation point, beyond which an electrician is needed to apply a higher level of understanding.

 

We could argue that given the requirement in the COP for a "competent" person to undertake appliance tests, the tester should be OK with devices from an IEC lead to 125A Ceeform to tails. In practice, the availability of simple "pass / fail" test equipment and the large number of relatively unskilled people who carry out appliance testing mean that three phase 'PAT' should be approached with caution.

 

Simon

 

* I noted that some places offering this course suggest it is 'suitable for anyone over 16', others state that it is "for electricians to understand the requirements of appliance testing" and (interestingly) one trainer states "Allows holder to PAT test single phase equipment ".

[grizzly]

However, the text you include suggests using other test equipment.

 

I would take this to mean when equipment is hardwired to a connection unit, rather than fitted with a ceeform plug, what with the mention of testing at terminals, and supply being isolated and proved dead.

 

I'd suggest that there are many people (perhaps even those who have passed the 2377 course*) whose knowledge is sufficient for basic testing, but does not extend to three phase systems etc.

 

I'd hazard a guess at that most people who hold 2377 couldn't be considered competent to do any more than basic testing, unless they'd had further training & experience.

 

I suspect that for many places, keeping basic appliance testing to devices that have a 13A plug (or a simple adaptation such as 13A to 15A) is a convenient demarcation point, beyond which an electrician is needed to apply a higher level of understanding.

 

I'd disagree that it would have to be an electrician, but definitely someone with a higher level of competence. I've met some 'qualified electricians' that I wouldn't trust to change a 13A plug!

 

We could argue that given the requirement in the COP for a "competent" person to undertake appliance tests, the tester should be OK with devices from an IEC lead to 125A Ceeform to tails. In practice, the availability of simple "pass / fail" test equipment and the large number of relatively unskilled people who carry out appliance testing mean that three phase 'PAT' should be approached with caution.

 

Absolutely.

Any tester should know their limits. There is an expanded Definitions section (section 2) in the 3rd edition CoP, that gives a good definition for 'Competent person'

[KevinE]

One of the problems is that 3-phase equipment is likely to include units which are of a rating such that the currents output from a standard PAT tester may not, for example show up a sub-standard earth bond which may fail under fault conditions if subject to (for example) a 63A supply. Also a load test won't be possible (excepting certain dimmer packs which simply split the load across phases) so that something like a blown internal fuse or breaker may prevent an insulation fault further downstream from failing on a PAT...something a 'human' inspection would find.

[lightsource]

How do you PAT test a Three Phase applience?

 

Sorry all, but I couldn't help but noticing........

Ok Dan, I don't know much about Star and Delta wiring but get what you mean

I was asked this question recently.. and didn't know either!

Well said... I know the boundary between "portable appliance" and "heavy duty piece of industrial machinery" can be a little blurred at times, but seeing as the IEE COP concentrates on 13A plugs, I wouldn't have considered portable appliance testing to be the best test method for such equipment.

Well...

 

IEE CoP for In-Service Inspection & Testing of Electrical Equipment (3rd edition), page 47:

Seems the IEE CoP is pretty clear on the matter.

OK... I have COP edition 1 and 2 - where that isn't stated! Looks like I have to fork out for a new book again!

I'd hazard a guess at that most people who hold 2377 couldn't be considered competent to do any more than basic testing, unless they'd had further training & experience

 

This is a subject I have interest in.... Heaven help me :)