3 Phase Insulation Resistance Test on motor & TP & N skt help

[blair1]

Looking for some advice on how to carry out a IR test on a 3-phase motor and a TP & N skt, these are parts of a module I have failed on a test and am looking to see where I am going wrong and what the normal procedure for carrying out this test would be?

 

[DavidSpark]

What assessment is it that you're doing? If people know then they can help tailor their answers if they have specific knowledge of key points that might need to be covered.

Could you provide a list of the steps that you did while testing and people could give pointers on your procedure.

However, with that being said.
I would do the following:
Assuming you have carried out safe isolation procedure.
Do closed circuit and open circuit test with IR tester to prove operation before testing commences, (0MΩ/>200MΩ).

AT THE DB
IR test between,

• L1-L2
• L1-L3
• L1-N
• L1-E

• L2-L3
• L2-N
• L2-E

• L3-N
• L3-E

• N-E

Once you have done that sequence of tests, and if you didn't have the contactor held in while doing this, you then repeat this process again from the load side of the motor control to prove the IR between the conductors feeding the motor socket, obviously being a balanced 3 phase motor it won't have a neutral so you you adjust your testing accordingly. once you have tested all those conductors then that should be the circuit IR tested.

Do closed circuit and open circuit test with IR tester to prove operation after testing has been carried out, (0MΩ/>200MΩ).

If anyone has anything to add or correct in what I have said, please do, so we don't have incorrect information being passed around.

 

[blair1]

sorry should have been more specific the 3 phase skt is a complete separate circuit from the motor and it is controlled by an isolator switch above it.

I carried out the following procedure at board for motor circuit (with incoming cables to motor disconnected) and for 3 phase socket circuit,

L1 - L2
L1 - L3
L2-3
L1 - N
L2 - N
L3 - N
L1 - E
L2 - E
L3 - E

I think what I missed out on was IR testing the outgoing SWA cable down to the motor.

Also, the isolator switch above the 3 phase skt was left in the on position aswell which I'm not sure would affect the outcome of the test?

 

[Gavin John Hyde]

Im useless at writing method statements for these things. Its alright in my head but useless when on paper.
I do recall there being somegood vids for this on youtube... Chris whats his name the guy who writes a lot of textbooks did them. I assume they still float around youtube....

 

[DavidSpark]

If those are indeed the steps you carried out then you missed the N-E IR test. There should be 10 total tests when doing IR on a three phase circuit. The exact same as proving dead coincidentally. It's easy to miss the cables going to the motor under the pressure.

The isolator being ON would affect the test, as in it would be testing the entire cable run and not just the cable up to the isolator its self which would be the case if it was in the OFF position.

I'd suggest going over your notes, checking on google for IR testing videos, there are lots around and generally just having a think about what the test is about and why its carried out. Understanding this will help you when it comes time to actually do it practically rather than just going through the motions because that's what you have to do.

 

[blair1]

ok all noted. thanks for that!

 

[ruston]

Im useless at writing method statements for these things. Its alright in my head but useless when on paper.
I do recall there being somegood vids for this on youtube... Chris whats his name the guy who writes a lot of textbooks did them. I assume they still float around youtube....

As suggested look up these videos . He is well respected.

.
I know this one is not quite what you are after , but they are worth viewing.

 

[Pete999]

Looking for some advice on how to carry out a IR test on a 3-phase motor and a TP & N skt, these are parts of a module I have failed on a test and am looking to see where I am going wrong and what the normal procedure for carrying out this test would be?

 

[David Prosser]

If you are I.R. testing the motor why can you not test all three phases to earth at the same time ?

 

[davesparks]

If you are I.R. testing the motor why can you not test all three phases to earth at the same time ?

If it’s permanently connected in star then you have no choice on the matter.

 

[Simonslimline]

sorry should have been more specific the 3 phase skt is a complete separate circuit from the motor and it is controlled by an isolator switch above it.

I carried out the following procedure at board for motor circuit (with incoming cables to motor disconnected) and for 3 phase socket circuit,

L1 - L2
L1 - L3
L2-3
L1 - N
L2 - N
L3 - N
L1 - E
L2 - E
L3 - E

I think what I missed out on was IR testing the outgoing SWA cable down to the motor.

Also, the isolator switch above the 3 phase skt was left in the on position aswell which I'm not sure would affect the outcome of the test?

Neutral - earth?

 

[Pete999]

Very unlikely that the 3 phase motor would have any Neutral connections?

 

[Simonslimline]

Very unlikely that the 3 phase motor would have any Neutral connections?

The TPN socket does.

If the motor CCT is anything like the AM2 setup then it will have a neutral brought in to the DOL starter.

 

[Pete999]

The TPN socket does.

If the motor CCT is anything like the AM2 setup then it will have a neutral brought in to the DOL starter.

Not always necessary to have a N at the starter could be a 400v coil,. but in answer to your question the AM2 is totally Alien to me. Could also be a completely different circuit from the Motor circuit, although I thought rightly or wrongly the OP was IR testing the Motor, could be I misread the post. I suppose in real life you would have the socket as close as possible to the actual motor, after the starter, so no N ,but as this is a testing facility for trainees I can see where the N at the socket would be required, may be this could send out the wrong signals to people who have no or very little 3 phase experience, something for the training establishments could think about, back to the motor, the OP was asking how to IR test a TP Motor, confusion may have set in at that juncture.

 

[Simonslimline]

Not always necessary to have a N at the starter could be a 400v coil,. but in answer to your question the AM2 is totally Alien to me. Could also be a completely different circuit from the Motor circuit, although I thought rightly or wrongly the OP was IR testing the Motor, could be I misread the post.

A bit more info needed from the OP perhaps!