Possible "Reverse phase" on 3ph motor.

[cameron456687]

Hi - first post here so go easy on me!

I have a 3-phase squirrel cage motor with 6 cables from the winding out to the terminal block, connected in delta. I've managed to group the cables in to 3 phases using a multi-meter - however I'm unable to to tell which is the beginning and which is the end of each phase. The motor is assembled so I'm unable to use dc and a compass and it's also coupled up so a bump test is proving difficult for the time being.

My worry is if I power the motor that one of the phases will be in reverse (see my terminal block mock-up below) and the current in that phase will go sky high and at worse burn out.

U1 V1 W2 U1 V1 W1
Instead of
V2 W1 U2 V2 W2 U2

Would using an oscilliscope help me solve my problem or will it be a case of trial and error?

Any help is apprecated.

Thanks.

 

[Skogsgurra]

If you have a three+ channel scope or a recorder. And if you can rotate the motor by hand - it can easily be found out if one of the windings is wrongly (false polarity) connected. Picture 5 in this (sorry Swedish) document shows what the voltafeges look like when wrong. Other pictures show correct connection, but wrong rotation.

http://www.google.se/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CC0QFjAA&url=http://

http://www.gke.org/arcus/files/ARCU...=oS8XnZV3h6_ogPf7uWrYBQ&bvm=bv.48175248,d.bGE

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[mpmembrebe]

You will need a 12V Battery and a multitester to identify motor leads, first is you have to determine 1,4(possibly it is 4,1), 2,5 (or 5,2) and 3,6 (or 6,3). Then connect the leads of multitester to one winding, (i. e. 1&4) and connect one lead of battery to the other windows. Momentarily connect the other lead of the battery to the pair lead and Record the deflection of the tester weather + or -.. Repeat the procedure to the other windows and marked all the positive deflection as 1,2,3 and negative deflection 4,5,6.

 

[petronila]

Hello Cameron

Looks like an IEC motor(Labelled witd letters and numbers), that nomenclature differs from NEMA motors (Only numbers).

If the wires are labelled then U1 V1 and W1 are start and U2 V2 W2 are finish, the motor will be well connected in Delta if U1 is jumped with W2, V1 jumped with U2 and W1 jumped with V2.

If the wires are not labeled then don´t disconnect any wire, label the upper wires (all connected in same line of the terminal block) like U1(left) V1 (center)and W1(right) to find the other labels (three wires down this line), disconnect the jumpers and Use a voltimeter in continuity mode and the wire that match with U1 is U2, the wire that match with V1 is V2 and wire that match with W1 is W2.


Once you finish the end result will be : Wire W2 down U1, wire U2 down V1 and wire V2 down W1. If this is true then connect again the jumpers(Vertical Way) and apply power in U1-W2, V1-U2 and W1-V2. Please Take a look of attachment.

Hope this can help you

Best Regards


Carlos