3-Phase Power Generation

What is the voltage induced in a phase called?

Phase voltage (Vphase)

What is instantaneous phase voltage and what’s the angle offset for 3-PH generation?

Phase voltage at any select instance of time, 3-phase gen. has A-PH @ 0, B-PH @ 120, C-PH @ 240 degrees

What phase sequence is positive, and which is negative? Is it in reference to clockwise or anti-clockwise rotation?

Pos = ABC, Neg = ACB, anti-clockwise reference

What does a star connected system look like?

Note: components connected at single point (neutral), not in series. Uses phases seperately, 240VAC from board usually

What does a star connection diagram look like?

What is the purpose of the neutral?

1. Allows 1-PH apparatus between itself and an active conductor
2. Carries out-of-balance current away in 3-PH

What is the current that goes through the neutral wire in an unbalanced system?

Neutral carries phasor sum of currents in phases, usually much less than line current.

What is the difference between phase voltage and line voltage?

Line to neutral voltage is phase voltage (measures 1 phase), line to line voltage is line voltage (measures two phases)

When measuring voltage for star-connected system, how should voltage be visualised?

Line voltages are connected at neutral, 415v is sent through all phases. 30 degree phase difference between them.

What does a delta connected system look like?

Connected in series, no neutral. 415VAC from board usually.

How does delta configuration not cause short circuit?

Since line + phase voltages are same, L1 + L2 + L3 VIR = 0 and no internal circulating currents in machine

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