phase difference

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Phase difference is also called "phase angle difference", "phase difference", "cycle difference" or "phase difference". The difference between the phases of two periodically changing physical quantities. When it is positive, it is said that the former is ahead of the latter, and when it is negative, it is behind the latter. When it is zero or an even multiple of π, the two physical quantities are in phase; It is called inverse phase when it is an odd multiple of π^[1] 。

Chinese name: phase difference
Foreign name: phase difference^[2]
Alias: differ

Nature: science
Category: Physics
Discipline: power engineering

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brief introduction

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Two with the same frequency alternating current The difference of phase is called phase difference, or phase difference. These two alternating current with the same frequency can be two AC current , can be two AC voltage , can be two AC electromotive forces, or any two of the three quantities. The phase difference between two sinusoidal quantities with the same frequency is equal to the difference of the initial phase. Is a constant that does not change with time. It can also be the phase change of current and voltage on a component. Any one sine The phase of the quantity y=Asin (wt+j0) is (wt+j0), and the phase difference between two sinusoidal quantities with the same frequency (independent of time t). If the initial phase of the first sine quantity is j01, and the initial phase of the second sine quantity is j02, then the phase difference between the two sine quantities is j12=j01 - j02.

Phase relation

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(1) When j twelve > When 0, the first sinusoidal quantity is said to be ahead of (or ahead of) the phase of the second sinusoidal quantity j 12；

(2) When j twelve < When 0, it is said that the first sine quantity lags behind (or lags behind) the phase of the second sine quantity| j 12|；

(3) When j When 12=0, the first sine quantity is said to be in phase with the second sine quantity;

(4) When j When 12=± π or ± 180 °, the first sine quantity and the second sine quantity are called Antiphase ；

(5) When j When 12=± π/2 or ± 90 °, the first sine quantity is said to be orthogonal to the second sine quantity.

Example

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1. Known u = 311sin（314 t - 30°） V， I = 5sin（314 t +60 °) A, then u And i The phase difference of is

jui = (- 30 °) - (+60 °)=- 90 °, i.e u than i 90 ° lagging, or i than u 90 ° ahead.

Value range and phase difference Primary phase Similarly, it is less than or equal to π (180 °). For those out of range, it can also be solved by adding or subtracting 2N π.

2. Research AC circuit Phase difference of.

If the circuit contains inductance and capacitance, the voltage phase of the pure capacitance circuit lags behind the current (the degree of voltage lag current can also be expressed as the degree of current lead voltage), Pure inductance circuit Current phase Lagging behind the voltage, the lagging phase value is half of π, or 90 °. When calculating the effective value of circuit current, capacitive current The lead is 90, the inductance is 90 behind, and the vector orthogonal decomposition and addition can be used.

Antiphase

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Applied to the base of transistor amplifier AC voltage And the AC voltage output from the collector, the phase difference between the two is exactly 180 °. This situation is called antiphase, or Antiphase 。

Special phase difference

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The orthogonal (90 °) and inverse (180 °) sine quantities are special phase differences.

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