|Rigid Rogowski Coils|
|Rigid Rogowski coils have a greater accuracy and stability than flexible coils and excellent rejection of interference caused by external magnetic fields. They are more suitable for low-current and low- frequency measurements.|
Rigid coils are wound on precision-machined plastic formers. Special machines are used to apply a precision winding. These precision techniques produce coils which have an exceptionally good rejection of interference caused by stray magnetic fields caused, for example by neighbouring conductors. All rigid coils are provided with electrostatic screening as standard to reduce noise and to minimise the effect of capacitive pick-up from the conductor voltage.
|Coil Type||A (mm)||B (mm)||C (mm)||Dimensions:
The table gives the dimensions for a number of standard coil sizes. We can also make other sizes.
The following gives typical values for a particular coil size. The actual specification will depend on the wire gauge used for the winding.
mutual inductance: 3 - 5 microhenries
current range (50Hz): < 100mA to > 100kA
upper frequency limit: 10 - 30 kHz
lower frequency limit: less than 0.1Hz
Rigid coils have a very stable output and can be calibrated to an accuracy of better than 0.1% using traceable standards. Their output is not affected significantly by the position of the conductor threading the coil.
The standard specification has been found useful for many applications. We can also make special coils to meet particular requirements for example: · Special material formers: for example to meet high temperature requirements or with specific expansion characteristics when coils have to be encapsulated · A test winding which allows the correct functioning of the coil to be monitored continuously · Coils wound on formers supplied by the customer.
We also make split rigid coils which can be fitted without disconnecting the conductor. These have a similar specification to the un-split coils. The output of a split current transformer is extremely sensitive to small changes in the gap between the two halves. Split Rogowski coils do not suffer from this problem
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