How to make a phase sequence using microcontroller?

[bluethunder7000]

phase sequence

hi

i would like to know how can i make a phase sequence using microcontroller and how can define the phases ( r s t ) and ( r t s )


thanks

 

[IanP]

Re: phase sequence

I assume that you would like to senese phases rather than generate them ..
To senese them you will need "zero crossing" detector or just simple optocouplers connected to each of them and 0Vac (earth).
Once you sense a phase crossing zero (sensing for rising or falling edge for all of 3 phases) - you can call it R and you will have to program your microcontroller to monitor both remaining phases for them to cross zero. This should occur at approximately 6.66666ms (for 50Hz system) for next phase, which you can call S, and after another 6.66666ms you will find phase T.
If a motor connected to this power point turns clockwise you have just defined the RST sequence ..
Now you can connect your device to an unknown power point and compare its sequence with that you have pre-defined in your microcontroller ..

 

[lats]

phase sequence

is there a non-microcontroller method with which we can do this. I tried below given circuit it worked very well. But when i used this circuit in parallel with my 3 phase voltmeter it gave problem. Probelm:- when one of the 3 phases isn't present i.e one phase is open i get voltage in that phase back, rougly around 108 Volts. Ideally it should be 0. I'm unable to find out the reason. I tried inserting some diodes in Phase sequence detector circuit, but no use. Can someone please help me . Thanks.