need help to find phase sequence

I am doing a project in which i have to synchronize two three phase alternators. I am able to monitor VOLTAGE and FREQUENCY of both alternators to compare them before synchronizing. I also need to monitor the phase sequence of both alternators before running the alternators in parallel. Could anyone please help me to find the phase sequence and compare them whether phase sequence of both the alternators are alike.

Do you have a small 3 phase motor that you could connect to each and see which way it spins?

No. i don’t have three phase motor. I have attached a journal paper with this post in which they have used opto-coupler to find the phase sequence.

V3I5-IJERTV3IS051720.pdf (727 KB)

Thought you only need to know if both alternators had the same [u]direction[/u] of rotation, looks like you need much more information. Do you have the components shown in figure 05?

you are right. I need much more information. Yes, i do have those components with me.

if there is any alternate method to find phase sequence you can suggest me. i can buy the components.

Please someone help he how to find phase sequence using Arduino mega 2560.

sachin88: I am doing a project in which i have to synchronize two three phase alternators. I am able to monitor VOLTAGE and FREQUENCY of both alternators to compare them before synchronizing. I also need to monitor the phase sequence of both alternators before running the alternators in parallel. Could anyone please help me to find the phase sequence and compare them whether phase sequence of both the alternators are alike.

Datasheet. I mean if these were tiny you'd just parallel them anyway and they would be self-synchronizing, if large that could burn out the windings or generally be bad.

If you sample the U winding of each and track zero-crossings that should give frequency and phase. A software phase-locked-loop is basically what you need. No-load voltages should be the same for the same frequency if they are identical alternators.

Could you please provide me any link which explains about PLL . How do i identify phase sequence using PLL?

sachin88: if there is any alternate method to find phase sequence you can suggest me. i can buy the components.

Oscilloscope....... multi-channel oscilloscope.

Otherwise you could maybe use the arduino to sample the voltages, and plot the sinusoidal voltages as a function of time. As long as you know which curve is which, then you can compare the phase.

But that would be manual if i'm not wrong. In my case if the load current of the first alternator is more than some threshold value then second alternator must run parallel to first. Before running it parallel arduino need to make sure frequency, voltage and phase sequence of both alternators are same. So i need a automatic phase sequence checker.

I see. In that case..... I agree. It will be good to use automatic phase difference measurement methods. This could involve converting the sinusoidal waveforms to square waves.... using voltage comparators with some applied hysteresis for handling noise. Then use a phase difference measurement method..... usually involving some circuitry that measures the time difference between rising edges of the two signals being compared. And also measuring period of the squarewave. From that info... you can then obtain phase difference. This can be done automatically. Maybe there are electronics packages that does this kind of thing for you.

sachin88: Could you please provide me any link which explains about PLL . How do i identify phase sequence using PLL?

You don't a phase locked loop is a control loop using phase difference - typically it controls an oscillator, here you'd have to affect one of the alternators or just use a phase detector by itself.

I agree. But i want make sure whether both alternators phase sequences are same to synchronize them.

For example, if first alternator phase sequence is RYB or ABC then even the second alternators phase sequence must be RYB or ABC to synchronize them. But i m confused how do i make sure whether the sequence is RYB or ABC?

sachin88: I agree. But i want make sure whether both alternators phase sequences are same to synchronize them.

For example, if first alternator phase sequence is RYB or ABC then even the second alternators phase sequence must be RYB or ABC to synchronize them. But i m confused how do i make sure whether the sequence is RYB or ABC?

Do you mean ABC or CBA?

RYB = Red Yellow Blue = ABC

you are right DLLOYD. RYB=ABC. It is to make sure both alternators are producing same phase. Hence i need to check phase sequence of both alternators. if they are same then turn on the contactor to run them in parallel.

Just some notes...

ABC sequence with A as reference:

A 0 deg B 120 deg C 240 deg

CBA sequence with A as reference:

A 0 deg C 120 deg B 240 deg

Interesting link ... could also check for missing phase.

EDIT: With Arduino, just need to measure the timing between zero-crossings to determine phase sequence or missing phases.

I think he's trying to idiot-proof it so if it's accidentally wired RBY, it doesn't try to connect ABC to ACB.

This is a tricky one because you are trying to connect things which may not share a common ground. The input electronics and protection circuits will be relatively complex. But once you've got all that sorted out and connected to the Arduino's 5V-only pins, then the programming should be relatively easy.

MorganS i agree with u that it won't be sharing common ground.

Bringing the voltage to 5V to feed to arduino is not a problem. Transformer's will provide the isolation as well. I really need help with " programming " part to check the phase sequence.

sachin88: Bringing the voltage to 5V to feed to arduino is not a problem. Transformer's will provide the isolation as well. I really need help with " programming " part to check the phase sequence.

This won't be just about programming. It will also involve hardware for making automatic phase difference measurements. Otherwise... I guess you could buy 'three-phase' sequence detectors... that does it all for you.... such as have indicators or outputs that tell you the phasing information.