AM2 DOL Motor

[Pete999]

Trying to get my head around something for a youngster I know about to study for AM2. Someone mentioned that one of the faults has something to do with the Motor running in the wrong direction and what is the way to reverse the rotation, I take it that the Motor is 3 phase am I correct? Not done the AM2 far to old and decrepit.

 

[gazdkw82]

Trying to get my head around something for a youngster I know about to study for AM2. Someone mentioned that one of the faults has something to do with the Motor running in the wrong direction and what is the way to reverse the rotation, I take it that the Motor is 3 phase am I correct? Not done the AM2 far to old and decrepit.

Hi pete,

Yeh it's a 3 phase motor.

If it's a fault then it will be on the fault finding section. Within this section there are many faults chosen at random. I think its 6 or 7 faults you have to find.

I never got this particular fault but I would say it would just be a case of continuity checking the phases from the DB to isolator, isolator to DOL and DOL to motor.

You only get a multimeter to use (low ohms, continuity)

 

[Pete999]

Hi pete,

Yeh it's a 3 phase motor.

If it's a fault then it will be on the fault finding section. Within this section there are many faults chosen at random. I think its 6 or 7 faults you have to find.

I never got this particular fault but I would say it would just be a case of continuity checking the phases from the DB to isolator, isolator to DOL and DOL to motor.

You only get a multimeter to use (low ohms, continuity)

Thanks Mate appreciated

 

[SparkyChick]

You only get a multimeter to use (low ohms, continuity)

I'm putting this out there because this isn't the first time I've seen this come up where it appears people are being limited to specific test instruments during the AM2.

If you're only being allowed access to a multi-meter, unless I'm much mistaken, the centre does not comply with the AM2 rules as laid out by NET. That is of course unless what you actually mean is a multi-function tester.

The whole point of the AM2 is to assess whether someone is ready to be out there and part of that is knowing what test gear to use. I've used a multimeter once for diagnosing a burglar alarm fault, everything else has been carried out using my MFT, my AVI or more suitable specialist testers (network cable tester, clamp meters etc.).

This is what NET have to say about the specification of a test centre when it comes to test gear...

"6. Each approved assessment centre will provide the following items of electrical test equipment one per two assessment units:

• 500v insulation/continuity tester (digital type)
• Line/earth loop impedance tester
• RCD tester
• Voltage proving unit
• Test lamp voltage indicator
• Continuity tester
• Phase rotation tester
• LAN tester
• BS 1363 socket outlet test connection plug

7. Multi-functional instruments may be used."

I believe you can use these at any time during the assessment, so you can do testing of your composite installation during the installation time if you wish and you should be able to pick up and use any of those items as appropriate for the fault finding section.

So, in this case I might be inclined to use a phase rotation tester to confirm the correct phase rotation along the entire 3p circuit. See Dave's post below

 

[davesparks]

So, in this case I might be inclined to use a phase rotation tester to confirm the correct phase rotation along the entire 3p circuit.

It is a few years now since I did the AM2 and this wouldn't have been possible when I did it, as fra as I can remember the fault finding rig wasn't connected to a source of supply. All of the fault finding was carried out dead and the Martindale bell set provided was all the test equipment required for it.

Also I think it would be better to check the phase sequence rather than the rotation in this scenario. We already know that there is a phase rotation problem as the motor turns the wrong way, what is not known is which two phases have been swapped.
A phase rotation test will only reveal where the swap has occurred, it won't reveal which two phases have been swapped. You would still need to follow it with a phase sequence check.

Plus of course they probably prefer it if you avoid live testing when a suitable dead test is possible.

 

[SparkyChick]

It is a few years now since I did the AM2 and this wouldn't have been possible when I did it, as fra as I can remember the fault finding rig wasn't connected to a source of supply. All of the fault finding was carried out dead and the Martindale bell set provided was all the test equipment required for it.

Also I think it would be better to check the phase sequence rather than the rotation in this scenario. We already know that there is a phase rotation problem as the motor turns the wrong way, what is not known is which two phases have been swapped.
A phase rotation test will only reveal where the swap has occurred, it won't reveal which two phases have been swapped. You would still need to follow it with a phase sequence check.

Plus of course they probably prefer it if you avoid live testing when a suitable dead test is possible.

It's only 12 months since I did mine and I can't remember whether there was a supply to the fault rigs and I don't do a lot of 3p work.... so to all trainees... I concur with Dave, this is the way to do it.

 

[gazdkw82]

No supply on the fault finding rig.

They do supply a multi function tester......for the testing section.

For the fault finding section there is a multi meter only.

 

[SparkyChick]

No supply on the fault finding rig.

They do supply a multi function tester......for the testing section.

For the fault finding section there is a multi meter only.

When I did my fault finding section I used the network cable tester, an AVI and the MFT.

There were no multi-meters present in the test centre that I could see, just the kit required by NET.

 

[gazdkw82]

When I did my fault finding section I used the network cable tester, an AVI and the MFT.

There were no multi-meters present in the test centre that I could see, just the kit required by NET.

We did have a network tester too.

I was also pre warned via the college that we would only be allowed a multi meter for fault finding. Tbh you can find all faults using a multi meter but I get what your saying.

The centre seemed pretty stringent followed the NET guidelines. I'd be very surprised if they strayed from them.

 

[davesparks]

When I did my fault finding section I used the network cable tester, an AVI and the MFT.

There were no multi-meters present in the test centre that I could see, just the kit required by NET.

There wasn't even any network cabling in the test when I did it.

The tester provided for the fault finding was an old Martindale bell set, which looked like a yellow block with two test leads hanging out of it and all it did was beep when there was continuity.

Like most people I was taught to use an analogue IR tester for fault finding (and still pretty much only use that) so it did seem a little odd to me.

 

[Conteh]

Does anyone know the equation to work out the output of the motor.

 

[Loki]

Does anyone know the equation to work out the output of the motor.

To work out the overload setting you:

 

[Lucien Nunes]

Purely out of curiosity, may I ask where that method came from? If from a course, was there any justification for the 10%?

 

[Loki]

Purely out of curiosity, may I ask where that method came from? If from a course, was there any justification for the 10%?

XS Training AM2S prep course

 

[davesparks]

Does anyone know the equation to work out the output of the motor.

Read it off from the motors data plate.
[automerge]1583700686[/automerge]

To work out the overload setting you:

View attachment 56227

I'm quite rusty on motors and their protection, but isn't that equation missing the motor efficiency?

Plus I don't really see why the 10% is added on?

 

[ElectroChem]

If I recall, the 10% was a fudge factor for when things like motor nameplate current, power factor, overload setting and supply voltage were... less than precise.
With modern motors, you should set the overload to the FLC of the motor.

 

[Lucien Nunes]

isn't that equation missing the motor efficiency

Indeed it is. That was part of my question about the 10%. Guess the pf, ignore the efficiency, but then add 10% for luck. Seemed like a less than ideal way to teach people to do things.

 

[davesparks]

Indeed it is. That was part of my question about the 10%. Guess the pf, ignore the efficiency, but then add 10% for luck. Seemed like a less than ideal way to teach people to do things.

They get away with it as the average electrician doesn't get anywhere near a motor or setting the overloads these days.

 

[Lucien Nunes]

To be fair, the setting will come out about right, but it's hard enough getting people to correctly interpret motor input and output power ratings. Suddenly making the distinction between the two disappear must be confusing.