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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Constant current transformer is of _______ type.
Core
Shell
Core or Shell
None of these
Shell
Quick Summary: A constant current transformer (CCT) is essentially a leakage-type transformer, which is typically constructed using a shell-type core. The design utilizes high leakage reactance to ensure that the secondary current remains independent of the load impedance within a specific range.
A constant current transformer (CCT) is essentially a leakage-type transformer, which is typically constructed using a shell-type core. The design utilizes high leakage reactance to ensure that the secondary current remains independent of the load impedance within a specific range.
Is≈XLVp — where XL is the leakage reactance
Φl=IpNp−IsNs — representing the leakage flux responsible for current regulation
The CCT is designed with a high degree of magnetic leakage between the primary and secondary windings. This is achieved by physically separating the windings on the central limb of the shell-type core, often using a movable coil assembly. When the load impedance increases, the secondary voltage increases to compensate, keeping the current constant; as the load impedance decreases, the leakage flux increases, restricting the current output to maintain a constant value.
Operates on the principle of variable magnetic leakage flux.
Used in series lighting circuits where constant current is required for series-connected lamps.
The primary and secondary coils are usually placed on the same limb with adjustable spacing.
Essentially acts as a self-regulating device against load variations.
Automatic regulation without external control circuits.
Robust construction for series street lighting systems.
Inherently short-circuit proof.
Lower efficiency compared to power transformers due to high leakage.
Low power factor.
Large physical size for a given KVA rating.
Series street lighting circuits.
Testing of electrical equipment requiring constant current.
Arc lamps and specialized industrial heating processes.
The shell-type construction provides a compact and mechanically stable structure for the movable coil mechanism.
Core-type transformers are generally used for high voltage transmission, whereas shell-type is preferred for magnetic flux control requirements like CCTs.
B is correct — Constant current transformers are specifically designed with a shell-type core construction to facilitate the high leakage flux path required for current regulation.
In competitive exams, remember that 'Leakage' and 'Constant Current' are keywords that point towards Shell-type construction due to the ease of flux control.