What is Rogowski coil ?
A Rogowski coil is a device for measuring alternating current (AC) or high speed current pulses. It is a coil of wire which is shown in figure. For measuring the current flow through any conductor, the rogowski coil is then covered around that conductor. It acts just like a current transformer , but there is no iron core.
Now describe how is it working :-
When current flows through the conductor, then some voltage produces in the rogowski coil. This voltage is directly proportion to the rate of change of current in the conductor. That means, induced voltage increases when the current flow increases and induced voltage decreases when the current flow decreases. An electronic integrator circuit is connected to the output of this the Rogowski coil to obtain that voltage. This integrator circuit is basically analog to digital converter which is often used for this purpose. And the output digital signal is used for current measuring purpose.
Some Advantages of this coil over other types of current Transformer are given below:-
- It can respond to fast-changing currents, , response time down to several nanoseconds.
- Due to absence of iron core, the output is highly linear even when subjected to large currents, such as those used in power system, welding or pulsed application.
- There is no risk on line opening of secondary winding.
- An installation cost is low than installation cost of current transformer.
- Temperature compensation is plain.
- For large current measuring, the rogowski coil is far smaller than the same ratting of current transformer.
Some Disadvantages of this coil over other types of current Transformer are given below:-
- Due to presence of integrator circuit, it requires 3 to 24V DC source. So, without DC source, the rogowski coil does not operated. It is the main disadvantage of rogowski coil over other types of current transformer.
Multiple Choice Question (MCQ) of Materials page-6:51. The permeability and permittivity of a medium are
A) independent of each other
B) related by the atomic number
C) related by the Boltzmann’s constant
D) related by the velocity of electromagnetic waves.
Multiple Choice Question (MCQ) of Materials page-5:41. Bakelite is
A) highly inflammable
B) low resistance conductor
C) a semi-conductor
Multiple Choice Question (MCQ) of Materials page-4:31. Which of the following pairs is commonly used in thermocouples?
D) Silver-German silver.