AM2 Testing 3 phase motor

reedy10 · Jul 17, 2011

Can someone help me out here I have my AM2 on tuesday and i`m a litle worried about the testing. How do you Zs on the motor circuit and commando socket or will my examiner allow me to do the calculation

Zs = Ze + (R1 + R2) and also for the PFC do you just measure each phase seperatly to neutral then double the highest reading.

Thanks in advance guys

steptoe · Jul 17, 2011

I have no idea,

maybe a mod could put this in the student section,

you may get more help there.

sorry, :|

Brian 157 · Jul 18, 2011

If safe to do so you could measure Zs on each line separately but I'd have thought calculation would be acceptable, it is in 2391. PFC is measured between line and earth, PSCC between line & neutral. As you say double the highest PSCC (line to neutral), this is an acceptable "rule of thumb" as outlined in GN3.

soulman · Jul 18, 2011

From what i can remember you only take a live zs from the socket circuit the others are calculated. pefc was measured each phase to earth and pscc was measured each phase to neutral. between phases was not measured and the total was not doubled as in gn3.(the examiner said we do not double it now that is the old way!) Yet i was taught at college that it should be doubled if not measuring between phases. Also i was taught at college just to check one phase to neutral and one phase to earth as the resistance of the 3 phase conductors should be the same.

pickleye · Jul 18, 2011

Just Passed my Am2 a couple of weeks ago - oh happy days!!!

We were told that ALL Zs's were to be calculated as it is safer (and quicker) - also mentioned that NICEIC is pushing for this to become the prefered method.

PEFC measured each line to Earth highest noted

PSCC all lines measured to Neutral, the highest value doubled (rule of thumb)

The highest of these two results is recorded as PFC.

Good luck hope all goes well.