Question

The total instantaneous power delivered by a three-phase generator under balanced operating conditions is

(a) A function of time

(b) A constant

Short answer

Answer

Therefore, the correct option is (b) “a constant”.

Step-by-step solution

Significance of star connection.

Write the formula for the instantaneous power delivered by the three phase system.

$$\begin{gathered} p_{a}t=V_{ah}\left(t\right)i_a\left(t\right) \\ \mathbf{=}\mathbf{2}{\mathbf{V}}_{\mathbf{LN}}\mathbf{}{\mathbf{I}}_{\mathbf{L}}\mathbf{}\mathbf{cos}\left(\mathrm{\omega t}+\delta \right)\mathbf{}\mathbf{+}\mathbf{}{\mathbf{V}}_{\mathbf{LN}}\mathbf{}{\mathbf{I}}_{\mathbf{L}}\mathbf{}\mathbf{cos}\left(2\mathrm{\omega t}+\delta +\beta \right) \end{gathered}$$ …… (1)

The above expression shows the power is not he function of time but it is the function of constant.

Define if statement is true or false.

From equation (1) it is clear that instantaneous power is the function of constant.

Thus, the correct option is “a constant”.