Page 162 - Electrician - TT (Volume 1)
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ELECTRICIAN - CITS
Inphase quantity
When two alternating quantities(current and voltage) attain their maximum and minimum values simultaneously ,
then these quantities are said to be in-phase.
Out of phase or (phase difference)
When two alternating quantities do not reach their maximum and minimum values simultaneously, then they are
out of phase. Phase difference is measured in electrical degrees or radiance .
Phase angle
It is the angular displacement between two alternating quantities. Phase angle is measured in electrical degrees
or radians. In figure VB is lagging VA by an angle ө.
Quadrature quantities
When the phase difference between two alternating quantities is 90° electrical ,they are said to be quadrature
quantities. In figure VB is lagging VA by 90°
Anti-phase quantities
When two electrical quantities are out of phase by 180° electrical, they are said to be anti-phase quantities.
Leading quantities
The alternating quantity that reaches its maximum value earlier than the other quantity is known as the leading
quantity. In figure VA leads VB by an angle ө.
Lagging quantities
The alternating quantity that reaches its maximum value later than the other quantity is known as the lagging
quantity. In figureVBlagsVA by an angle ө.
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CITS : Power - Electrician & Wireman - Lesson 26-29
