View Full Version : Links on a 3 phase motor

Daz man
19-11-2011, 11:51 PM
Hi folks,

Probably a really easy question for most, but I am carrying out a 3 phase electric motor test on Monday on quite a large 'Brooke Crompton' motor from an AHU and just wanted to know if I have to remove the metal links (strappers) inside the terminal box of the motor?

Imagine a number 6 on a dice, I have each of the 3 phases on one side and then links which connect each phase to the other 3 terminals inside the terminal box.

I understand how to use my 'Megger' but wasn't sure if I touch one of my probes to each of the terminal pins (x6 if I remove the links) and the second probe to ground or one probe to each of the terminal pins (x3 if the links stay in) and the second probe to ground

Feed back appreciated

Apologies for very poor description, really hard to describe what I mean in words

install monkey
19-11-2011, 11:56 PM
leave the links in situ- test from the outgoing side of the contactor- sure test the connections to see if theyre tight but to test the insulation- black probe on the earth of the motor casing,earth terminal- ensur paint isnt affecting the connection,red probe on each phase in turn and over 1meg ohm is ok,usually goes to infinity or over 300 meg ohms-under 1 meg will trip a rcd,0.0meg ohms and its a dead short,test resistance on the windings to ensure theyre equal

20-11-2011, 12:14 AM
as install monkey said, and also whilst onsite check the contactors also ensure you dont have a phase down through the contactors.
not trying to insult your inteligence just a thought if not already done.

Daz man
20-11-2011, 09:05 AM
Cheers men, thanks for the feedback