Page 190 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

The phase sequence of the three-phase system may be reversed by interchanging the connections of any two of
the three phases.
Phase-sequence indicator using choke and lamps: The phase-sequence indicator consists of four lamps and
an inductor connected in a star formation (Y). A test lead is connected to each leg of the `Y’. One lamp is labelled
U-V-W, and the other is labelled U-W-V. When the three leads are connected to a three-phase line, the brighter
lamp indicates the phase sequence. (Fig 3)
Phase-sequence indicator using capacitor & lamps: The phase-sequence indicator consists of four lamps and
a capacitor connected in a star formation (Y). A test lead is connected to each leg of the `Y’. One pair of lamps
are labelled U-V-W,and the other pair are labelled U-W-V. When the three leads are connected to a 3-phase line,
the brighter lamp indicates the phase sequence. (Fig 4)

Fig 3 Fig 4

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CITS : Power - Electrician & Wireman - Lesson 26-29