How to introduce a phase shift in an AC circuit

[lcr2139]

Hello, I am trying to think of a way to introduce a phase shift in an ac circuit. For example, sin(omega*t+theta) to change theta. How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors). A transformer would not work either. What do you think?

 

[berkeman]

Hello, I am trying to think of a way to introduce a phase shift in an ac circuit. For example, sin(omega*t+theta) to change theta. How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors). A transformer would not work either. What do you think?

Depends on the rest of the circuitry and the frequencies involved. Worst case you can use an ADC + DAC with a RAM buffer in the middle to introduce a delay (hence a phase shift from the original signal).

Can you post a schematic and a more complete description of the circuit/system please? Thanks.

 

[anorlunda]

Hello, I am trying to think of a way to introduce a phase shift in an ac circuit. For example, sin(omega*t+theta) to change theta. How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors). A transformer would not work either. What do you think?

Of course an inductor or capacitor will work. What are you thinking?

Perhaps you mean a voltage signal with no current (no load). You want to shift it by a defined and variable angle Θ, still with zero current. Is that what you are asking?

 

[NascentOxygen]

I am trying to think of a way to introduce a phase shift in an ac circuit.

Is the frequency fixed? You want a variable phase shift over what range? Is this for a small signal circuit or is it a power circuit?

 

[jim hardy]

have you studied electricity at all ?

We need some clue at what level to phrase an answer.

old jim

 

[Baluncore]

How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors).

Ye of little faith. We have been shifting phase with capacitors and inductors for over 100 years. It is important that those who say it can't be done, should not interrupt those who are doing it.

Given a sinewave x, you could generate a 90° shifted wave y, = quadrature, then sum a blend of the original x with the quadrature y to give any phase shift you want.

Why do you want to shift the phase?

 

[CWatters]

Hello, I am trying to think of a way to introduce a phase shift in an ac circuit. For example, sin(omega*t+theta) to change theta. How can I go about doing this? I do not think introducing a cap or inductor would work, even though it shifts the voltage from the current graphs (phasors). A transformer would not work either. What do you think?

You said "omega*+theta" which if I remember correctly means you want the output voltage to lead the input.

The current through a capacitor leads the voltage so you just need to put that current through a resistor to turn it back into a voltage :-)

See high pass filter...

https://www.electronics-tutorials.ws/filter/filter_3.html

...we can see that the phase angle ( Φ ) of the output signal LEADS that of the input and is equal to +45o at frequency ƒc.

Edit: I should add that there will be side effects such as a loss of amplitude and the phase shift will be different for different frequencies. This is behind some of the questions others have asked above.

 

[tech99]

The current through a capacitor leads the voltage so you just need to put that current through a resistor to turn it back into a voltage :-)

See high pass filter...

https://www.electronics-tutorials.ws/filter/filter_3.html
.

May I mention that phase shift network always has to have resistance somewhere.

 

[berkeman]

May I mention that phase shift network always has to have resistance somewhere.

Not mine! (post #2)

 

[anorlunda]

Unfortunately, the OP has not been back to PF since posting this thread.

 

[yungman]

You definitely can use cap or inductor to introduce phase shift. OP needs to give the parameters, what frequency, what phase shift.

If the frequency is high ( over 100MHz), you can use delay line to create a fix phase shift.

 

[tech99]

You definitely can use cap or inductor to introduce phase shift. OP needs to give the parameters, what frequency, what phase shift.

If the frequency is high ( over 100MHz), you can use delay line to create a fix phase shift.

Even with a delay line, it requires a resistive termination in order to shift phase.

 

[Baluncore]

Even with a delay line, it requires a resistive termination in order to shift phase.

Yes, but that termination might be a zero or infinite value of resistance.
Is an open circuit a resistor?

 

[yungman]

Even with a delay line, it requires a resistive termination in order to shift phase.

So we use a terminating resistor.

 

[tech99]

Yes, but that termination might be a zero or infinite value of resistance.
Is an open circuit a resistor?

If the delay line is terminated in an open circuit, we have entirely standing waves on the line. This means that no net energy is flowing from generator to load. In this situation you can have zero or 180 degree phase shift only.
If we progressively change from total mismatch to perfect match, we find that the phase shift changes from being all at one point (0/180) to gradually spreading out along the line.
This topic is discussed in "Radio Engineering" by Terman. It is sometimes of importance in the case of phasing lines for antennas.

 

[eq1]

Because of the vagueness of the question I suspect this is actually a paraphrased homework assignment asking the student to come up with an all pass filter.

https://en.m.wikipedia.org/wiki/All-pass_filter

 

[jim hardy]

Unfortunately, the OP has not been back to PF since posting this thread.

Once again we find ourselves "Seduced and Abandoned" ?

Close it ?

 

[dvscrobe]

@lcr2319, capacitive or inductive reactance does introduce a phase shift. If the impedance changes, the current will shift from your voltage reference that you are using. So, therefore, introducing a capacitor or inductor into the circuit would cause a phase shift. Dan