Exam Question
(a) Explain about Single Phasing Protection for poly phase motor (6)
(b) A 440V, 10Kw, 0.8 p.f, 3phase load is supplied as shown. Calculate short circuit fault current at the load and at the main switch board (10)
Class 4 (4th Engineer)
MET
📅 Jul 2022
Reference Answer
### (a) Single Phasing Protection for Polyphase Motors (6 Marks)
#### 1. Definition of Single Phasing
Single Phasing is a fault condition in a three-phase system where one of the three supply lines to a motor becomes open-circuited or 'dead'. As stated in the reference, this is also known as 'Open Phasing' or 'Phase Failure'. It is a severe form of voltage unbalance where the voltage in one phase drops to zero. This can be caused by:
* **Blown Fuse:** A fuse in one of the three lines blowing due to a transient overcurrent or fault.
#### 1. Definition of Single Phasing
Single Phasing is a fault condition in a three-phase system where one of the three supply lines to a motor becomes open-circuited or 'dead'. As stated in the reference, this is also known as 'Open Phasing' or 'Phase Failure'. It is a severe form of voltage unbalance where the voltage in one phase drops to zero. This can be caused by:
* **Blown Fuse:** A fuse in one of the three lines blowing due to a transient overcurrent or fault.
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