star delta rotation ? 1

[0831]

Hello to all and thanks for all your very informative input, i have searched through the forums but don't seem to be able to find my answers hence my questions, it has been a few years since i installed motors so my knowledge was rusty, I am wiring a 45kw 3ph 415v motor and am taking 2 16mm2 swa 3 cores from the control panel in which there are the usual star/delta contactors, i am concerned with rotation of the motor - in star it is quite easy to alter direction if need be but when the contactor switches to delta i need to know that the delta wiring will be in the same direction as the star wiring when it kicks in, i don't own a fluke rotation tester but if i get the wiring wrong i am assuming i will be forcing the motor to a sudden stop then calamity any suggestions will be most helpful

 

[Skogsgurra]

Can't you do two "bump tests"? Once in Wye and once in Delta? That would avoid the dreaded reverse from Wye when Delta is activated.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Marke]

When you connect a star delta starter, you connect one end of the windings to the main contactor and the other end of the windings to the junction between the star contactor and the delta contactor.
In both star and delta, the direction of rotation is determined by the connection to the main contactor.
At the other end of the windings, if you accidently reverse the rotation of the connections, the motor will not run in revers, it will end up with one winding going to a leading phase, one winding going to a lagging phase and one winding going back on to the same phase. It will draw lots of current on two phases and hopefully trip out.
The connections are easy to check out with an ohmmeter.
Ensure that the three phases are connected across the inputs of the main and delta contactors in a manner that is easily identified. I always prefer the same order across them left to right, then with the motor connected and no power applied, measure the resistance from phase 1 output of main contactor to phase 1 output of delta contactor and there should be an ope circuit. do the same for phase 2 and phase 3 and you are then in a connection that will work. If you have a low resistance between the outputs of the two contactors on the same phase, you have a problem. If all phases show a low resistance, you have the windings coming back onto the same phase, so roll the motor connections on the delta contactor one phase in the same direction. If one phase has a low impedance, then the rotation is reversed on the delta conatctor, so reverse the connections onto the delta contactor then recheck.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[0831]

Thanks for the replies, I have to say that were I totally on my own then "bump" tests would be done in the absence of test instruments, yes i remember (thanks marke )now my old ex navy mentor telling me off several times for not rmembering whilst i was his apprentice.

The second part is: using a rotation meter to ensure correct rotation before switching on the motor, i am in the process of buying one but if anyone has any comments on "using one" i wait with interest.