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Modern Electrical Installation for Craft Students, 3rd Edition
book

Modern Electrical Installation for Craft Students, 3rd Edition

by Brian Scaddan
November 2013
Intermediate to advanced content levelIntermediate to advanced
182 pages
6h 6m
English
Newnes
Content preview from Modern Electrical Installation for Craft Students, 3rd Edition
Cells, batteries and transformers 59
Diagram 70 Bar primary transformer
measurements. The most common form is the bar primary type
(Diagram 70).
It is clearly impracticable to construct an instrument to measure
currents as high as say 200-300 A, so a current transformer is used to
step down the secondary current to a value which can be measured on a
standard instrument.
Example 4.3
A current of 300 A flowing in a bus-bar needs to be measured. The
ammeter available has a maximum rating of 0.5 A. How many turns on
the secondary of a current transformer would be required to measure the
primary current? where N
p
=
1
(single bus-bar); I
p
= 300 A ...
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Publisher Resources

ISBN: 9781483106205