with a sufficient precision of
1%. The current-time product is also very relevant to the
precision of the measurement, so product datasheets for current transformers include
information about theseparameters.
The principle of the current transformer is found in a commercial product in the
Coil from the company
of the same name. Current transformers are
availablewith different levels of sensitivity, i.e. the ratio per ampere to the output voltage
aswell as themaximum pulse currents.
NoDC and low frequency current
Typically difficult integration into
the load circuit
Can bedirectly connected toan
Negligible influence to load circuit
Risk of damage at very large
currents above the nominal
Advantages and disadvantages of current transformers
188.8.131.52 Rogowski coil
are air-cored coils, i.e. they do not have a core. They comprise a
conductor, wound around and into the same shape as a non-ferromagneti
which serves as a mechanical carrier. To measure a current, the Rogowski coil is
placed around the conductor. Alternating current I
flowing through this conductor will
induce a voltageU
in theRogowski coil.
⋅ = ⋅
: Magnetic field constant
H 10 4
: Number of windings
A: Area surrounded [m
l: Average girth of the coil [m]
L: Inductance of the coil [H]
Named after Paul Pearson from theUnitedStates.
For the sake of completeness, othermanufacturers of current transformers based on the same principle should
be named here. These include, for example, Lilco Ltd. and IPEC Ltd. The choice of the correct converter will
depend partly on whether an internal termination resistor (burden) is already integrated or not. When the
transformer is operated without this burden or with an open output, dangerously high voltages can occur which
maydamage the converter and/or createa hazard for the persons using the device.
Named after German electrical engineerWalter Rogowski (1881 - 1947), who published the principle in 1912,
based on thework of English physicist Arthur PrinceChattock (1861 - 1934).
Ferromagnetic substances, when exposed to amagnetic field, becomemagnetised themselves.