Phase shift

Phase shift is the difference between the initial phases of two variables that change in time periodically with the same frequency . The phase shift is a dimensionless quantity and can be measured in radians ( degrees ) or fractions of a period. With a constant, in particular, zero phase shift, one speaks of the coherence of the two processes. Phase (phase angle) is called the angle $\varphi =2\pi {\frac {t}{T}},$ ${\ displaystyle \ varphi = 2 \ pi {\ frac {t} {T}},}$ ${\ displaystyle \ varphi = 2 \ pi {\ frac {t} {T}},}$ Where $T$ ${\ displaystyle T}$ $T$ - period $t$ ${\ displaystyle t}$ $t$ - the proportion of the phase displacement period when sinusoids are superimposed on each other. So if the curves (variables - sinusoids: oscillations , currents ) are shifted relative to each other by a quarter of the period, then we say that they are phase shifted by ${\frac {\pi }{2}}~(90^{\circ }),$ ${\ displaystyle {\ frac {\ pi} {2}} ~ (90 ^ {\ circ}),}$ ${\ displaystyle {\ frac {\ pi} {2}} ~ (90 ^ {\ circ}),}$ if on the eighth part (share) of the period - then, then on ${\frac {\pi }{4}}$ ${\ displaystyle {\ frac {\ pi} {4}}}$ ${\ displaystyle {\ frac {\ pi} {4}}}$ etc. ^[1]
When it comes to several phase-shifted sinusoids, technicians talk about current or voltage vectors. The length of the vector corresponds to the amplitude of the sinusoid, and the angle between the vectors corresponds to the phase shift. Many technical devices give us not a simple sinusoidal current , but one whose curve is the sum of several sinusoids (respectively, phase shifted).

To measure the phase shift between two electrical signals, an electric measuring device, a phase meter, is used .

A phase detector is a device that compares the phases of two input signals and generates a signal proportional to the difference in their phases.

In electrical engineering, a phase shift between voltage and current determines the power factor in AC circuits .

In radio engineering , RC chains are widely used, which shift the phase of the input and output signal of the RC chain, depending on the resistance and capacitance parameters in the circuit. It is used in RC generators .

Induced in the secondary windings of an ideal EMF transformer for any form of current, it coincides in phase and shape with the EMF in the primary winding. When the windings are turned off in phase, the transformer changes the polarity of the instantaneous voltage to the opposite, in the case of a sinusoidal voltage it shifts the phase by 180 °. It is used in the Meissner generator and others.

Notes

↑ See also Oscillation Phase. # Related Terms

Phase shift

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