Chapter 12, Problem 1RQ

What is the phase sequence of a three-phase motor for which and ?

(a) abc

(b) acb

To determine

Choose the correct option that provides the required phase sequence of a three-phase motor.

Answer to Problem 1RQ

The correct option is $\underset{\_}{\left(\text{a}\right)abc}$.

Explanation of Solution

Given data:

Consider that the given voltages.

$V_{AN}=220\angle -100°\text{V}$

$V_{BN}=220\angle 140°\text{V}$

Calculation:

Refer Figure 12.7 (a) in the textbook for the abc sequence that is also known as positive sequence.

The value of voltage $V_{AN}$ is,

$\begin{array}{c}{V}_{AN}=220\angle -100°\text{V}\\ =220\angle 360°-100°\text{V}\\ =220\angle 260°\text{V}\end{array}$

Write the expression for the voltage $V_{BN}$ for the abc sequence.

$V_{BN}=V_{AN}\angle -120°$

Substitute $220\angle 260°\text{V}$ for $V_{AN}$.

$\begin{array}{c}{V}_{BN}=\left(220\angle 260°\text{V}\right)\angle -120°\\ =220\angle 260°-120°\text{V}\\ =220\angle 140°\text{V}\end{array}$

Hence, the abc sequence is verified for the given voltages.

Therefore, the option (a) is correct and option (b) is incorrect.

Conclusion:

Thus, the correct option is $\underset{\_}{\left(\text{a}\right)abc}$.