# Exam question regarding saturation test of a 1500/5 multi-ratio CT

1. ## Exam question regarding saturation test of a 1500/5 multi-ratio CT

During a saturation test of a 1500/5 multi-ratio CT, 400 volts is applied to the X1 to X4 tap. The X1 to X4 tap is the 1200/5 ratio. What is the expected voltage across the X1 to X5 tap?

Can we have clarification on what the question is suggesting? Are you applying 440 V directly on the taps? Aren't the X4 and X5 taps the same point, electrically, and would therefore have the same potential voltage?

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Originally Posted by Tseppish
During a saturation test of a 1500/5 multi-ratio CT, 400 volts is applied to the X1 to X4 tap. The X1 to X4 tap is the 1200/5 ratio. What is the expected voltage across the X1 to X5 tap?

Can we have clarification on what the question is suggesting? Are you applying 440 V directly on the taps? Aren't the X4 and X5 taps the same point, electrically, and would therefore have the same potential voltage?
The 0V is the correct answer.
The CT is not like an "autotransformer". The circuit is closing thru x1-x4. There is no current flowing on X5. So zero current = zero voltage.

3. Originally Posted by nscdrgs
The 0V is the correct answer.
The CT is not like an "autotransformer". The circuit is closing thru x1-x4. There is no current flowing on X5. So zero current = zero voltage.
Agreed. This question has kind of tricky wording.

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## During saturation test, Multi-tap CT is an autotransformer

Originally Posted by SecondGen
Agreed. This question has kind of tricky wording.
The voltage across X1-X5 in the condition described will be 500V. 1500/1200 X 400 = 500