You can use a voltage transformer, not a regular 3 phase, but three independent and equal ones. Connect their outputs in series. If the phases and voltage for 3 phase is correct, the sum of voltages should be zeero.I want to build the circuit that will monitor the voltage sequence of 3 phase supply and i want it will only give me the signal when the sequence is incorrect. How can i implement this without using zero crossing?
Depends of the device/circuit that is meassuring the current value.Second how to calculate the turn ratio, and current values to design the current transformer (assume my load is of 6A)?????
The CT is very simple to design. You just a iron core (for transformers) and wind it woth two set of windings so you get a turn ratio. Or is it the CT itself you are not sure how to design?Can you tell me how to design a CT if i know the load current ????
Well, it's hopeless when you don't know what current you want on secondary side. It's just like an equation with two unknown, cannot solve until you make up your mind and decide what current you want on the output. Unless you have more info I really cannot help you?I only wanna know how to calculate the turn ratio.
At primary there are 2-5 turns, i guess, and for secondary i dont know...........
Wrong. Because a ct isn't supposed to output any voltage - exept for a very small voltage. And it's also supposed to be connected to some equipment that can sense when current is too high so any connected components (usually in power grid) can be disconnected from the rest of the power grid.If i design the CT like PT then it means current will step down and voltage ll step up.....how to handle that much voltage???????
Am i right or wrong??????????
You generally put a burden resistor on the secondary so that the transformed current creates a voltage which is proportional to primary current. So if your primary has 1 turn and your secondary has 10, and you have a 1 ohm burden resistor then you will get 0.1V per amp. That is assuming your magnetizing impedance is much greater than 1 ohm. If you want to lower the secondary voltage, then you lower the burden resistance.I only wanna know how to calculate the turn ratio.
At primary there are 2-5 turns, i guess, and for secondary i dont know...........
If i design the CT like PT then it means current will step down and voltage ll step up.....how to handle that much voltage???????
Am i right or wrong??????????
Assuming the transformers are star connected (each one between phase and neutral), then zero output will indicate phase symmetry, but not correct sequence. The sequence may be reversed as well. A phase sequence detector always involves a phase shifter or similar circuit as a reference for the observed sequence.You can use a voltage transformer, not a regular 3 phase, but three independent and equal ones. Connect their outputs in series. If the phases and voltage for 3 phase is correct, the sum of voltages should be zero.
Well, it's hopeless when you don't know what current you want on secondary side. It's just like an equation with two unknown, cannot solve until you make up your mind and decide what current you want on the output. Unless you have more info I really cannot help you?
If you have technical question, feel free to ask. I beleive you don't really know how to use a ct.
Assuming the transformers are star connected (each one between phase and neutral), then zero output will indicate phase symmetry, but not correct sequence. The sequence may be reversed as well. A phase sequence detector always involves a phase shifter or similar circuit as a reference for the observed sequence.
You generally put a burden resistor on the secondary so that the transformed current creates a voltage which is proportional to primary current. So if your primary has 1 turn and your secondary has 10, and you have a 1 ohm burden resistor then you will get 0.1V per amp. That is assuming your magnetizing impedance is much greater than 1 ohm. If you want to lower the secondary voltage, then you lower the burden resistance.
Ok. Let's assume that 10mA is the maximum current that you want to read (given you have choosen a resistor so voltage can be dropped over). Then the turns ratio must be 6A/10mA = 600.Basically i want to interface the ct with ucontroller, so the secondary current should be within safe range (5ma-10ma).
How many phases do you need to swap to achieve a change in the sequence?how to correct them??? I have tried it by using relays but they only change the yellow and blue phases.
Do you have a regular 3 phase transformer with known identity of the input phases?
How many phases do you need to swap to achieve a change in the sequence?
Why do you want to swap it? To get a motor run in reverse? Then it doesn't matter wich two phases you chose to swap. It will have the same effect.Basically i want to correct the sequence; if fault occurs. Only two of them need to swap. But the problem is which ones??
Why do you want to swap it? To get a motor run in reverse? Then it doesn't matter wich two phases you chose to swap. It will have the same effect.
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