1) Describe, with the aid of sketches, the mechanisms built into the design of an HRC fuse link to enable it to respond efficiently to a sustained overload as well as to a severe short-circuit condition
1) Describe, with the aid of sketches, the
2) Explain the significance of ‘let-through energy’ when assessing discrimination between major and minor fuses in a system of feeder protection. Describe how manufacturers’ data can be used in this assessment.
3) Attached figure shows a time-current characteristic typical of miniature circuit breakers. Explain how such a characteristic can be achieved in the construction of an MCB. In what respect would the actual characteristic of Type D MCB differ from that of Type B of the same rating? What significance does this difference have on the application of each type?
4) In general, HRC fuses provide back-up protection for the overload protection relay incorporated in an induction motor starter. Define the two types or levels of back-up protection that could be provided and explain the difference between these two forms of protection and show how the two protective devices should be co-ordinated.
![Time s
0.1s----
Prospective current A
Fig 1: Typical time-current characteristic of MCB](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F21485b33-a6fd-41c6-9cba-f39047ccb4f2%2Fe8f7ee0d-dbde-444e-aaad-55c657d0a35e%2Fjg86lys_processed.png&w=3840&q=75)
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