Carl Emil Krarup
Encyclopedia
Carl Emil Krarup was a Danish telegraph engineer who is chiefly known for the invention of a kind of loaded cable
, eponymously called Krarup cable, which made improvements in the transmission of telephone signals, especially on submarine cables
.
in Germany on loaded lines. Returning to Denmark he continued the theoretical work at the University of Copenhagen
and published a paper in 1902.
to reduce their distortion. All methods of loading add series inductance
to the cable to try to meet the Heaviside condition
for no signal distortion. Krarup cable consists of iron wires wound tightly around the copper conducting cores and it is the iron that is the source of the additional inductance. However, it still does not have sufficient inductance to fully meet the Heaviside condition. Its construction also makes it expensive compared to the previously existing method of adding discrete loading coils at intervals along the cable. Against this, Krarup cable is lighter and easier to lay. The weight of early submarine cables using loading coils could cause excessive stress in the cable if not handled carefully. Additionally, Krarup cable has none of the problems of sealing the joins against seawater which was a major problem with loading coils before modern polymers began to be used.
For these reasons, Krarup cable was popular on shorter distances, where the distortion was not so high that loading coils had to be used, until the advent of permalloy
cable superseded it. The first cable to be laid with Krarup cable, indeed the first cable to be laid with any kind of continuous loading, was between Helsingør (Denmark) and Helsingborg
(Sweden) in 1902. This cable was engineered by Krarup himself.
Loading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
, eponymously called Krarup cable, which made improvements in the transmission of telephone signals, especially on submarine cables
Submarine communications cable
A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean....
.
Career
Krarup was originally a civil engineer. He was in charge of public works in Copenhagen until 1898 when he joined the Danish Telegraph Administration. In 1901 he conducted research at the University of WürzburgUniversity of Würzburg
The University of Würzburg is a university in Würzburg, Germany, founded in 1402. The university is a member of the distinguished Coimbra Group.-Name:...
in Germany on loaded lines. Returning to Denmark he continued the theoretical work at the University of Copenhagen
University of Copenhagen
The University of Copenhagen is the oldest and largest university and research institution in Denmark. Founded in 1479, it has more than 37,000 students, the majority of whom are female , and more than 7,000 employees. The university has several campuses located in and around Copenhagen, with the...
and published a paper in 1902.
Krarup cable
Krarup cable is a method of loading linesLoading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
to reduce their distortion. All methods of loading add series inductance
Inductance
In electromagnetism and electronics, inductance is the ability of an inductor to store energy in a magnetic field. Inductors generate an opposing voltage proportional to the rate of change in current in a circuit...
to the cable to try to meet the Heaviside condition
Heaviside condition
The Heaviside condition, due to Oliver Heaviside , is the condition an electrical transmission line must meet in order for there to be no distortion of a transmitted signal...
for no signal distortion. Krarup cable consists of iron wires wound tightly around the copper conducting cores and it is the iron that is the source of the additional inductance. However, it still does not have sufficient inductance to fully meet the Heaviside condition. Its construction also makes it expensive compared to the previously existing method of adding discrete loading coils at intervals along the cable. Against this, Krarup cable is lighter and easier to lay. The weight of early submarine cables using loading coils could cause excessive stress in the cable if not handled carefully. Additionally, Krarup cable has none of the problems of sealing the joins against seawater which was a major problem with loading coils before modern polymers began to be used.
For these reasons, Krarup cable was popular on shorter distances, where the distortion was not so high that loading coils had to be used, until the advent of permalloy
Permalloy
Permalloy is a nickel-iron magnetic alloy, with about 20% iron and 80% nickel content. It is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields...
cable superseded it. The first cable to be laid with Krarup cable, indeed the first cable to be laid with any kind of continuous loading, was between Helsingør (Denmark) and Helsingborg
Helsingborg
Helsingborg is a city and the seat of Helsingborg Municipality, Skåne County, Sweden with 97,122 inhabitants in 2010. Helsingborg is the centre of an area in the Øresund region of about 320,000 inhabitants in north-west Scania, and is Sweden's closest point to Denmark, with the Danish city...
(Sweden) in 1902. This cable was engineered by Krarup himself.