Understanding Phase Sequence Indicator Rotation

A phase sequence indicator is a device used to determine the order or sequence in which the voltage peaks of a three-phase system occur. The direction of rotation of the indicator depends directly on this phase sequence.

The question provides a specific condition: when the phase sequence is RYB (Red, Yellow, Blue), the indicator rotates clockwise.

Now, we need to determine what happens when the phase sequence is changed to BRY.

Analyzing Phase Sequences RYB and BRY

Let's look at the order of phases:

• RYB: The sequence is typically considered R > Y > B > R in a cycle.
• BRY: The sequence is considered B > R > Y > B in a cycle.

Comparing the two sequences (RYB and BRY) in a cyclic manner:

• Starting from R in RYB, we go to Y, then B, then back to R.
• Starting from B in BRY, we go to R, then Y, then back to B.

These two sequences, RYB and BRY, are actually cyclic permutations of each other. If you shift the starting point of RYB, you get YBR, and shifting again gives BRY. All cyclic permutations of a sequence (like RYB, YBR, BRY) represent the same fundamental phase rotation direction.

The opposite phase sequence to RYB would be RBY (or its cyclic permutations like BYR or YRB). Swapping any two phases in RYB results in the opposite sequence (e.g., swapping Y and B in RYB gives RBY).

Determining Rotation Direction for BRY

Since BRY is a cyclic permutation of RYB, it represents the same phase sequence direction as RYB.

Given that the phase sequence indicator rotates clockwise for RYB, it will also rotate in the same direction for any cyclic permutation of RYB.

Therefore, for the phase sequence BRY, the indicator will rotate clockwise.

This aligns with the understanding that a phase sequence indicator rotates in one direction for one set of cyclic sequences (like RYB, YBR, BRY) and in the opposite direction for the other set (like RBY, BYR, YRB).

Based on the initial condition, if RYB causes clockwise rotation, then BRY (being in the same cyclic family) will also cause clockwise rotation.

Thus, when the phase sequence is changed to BRY, the phase sequence indicator will rotate clockwise only.