To meet increasing customer demand, Power Electronic Measurements (PEM) Ltd, has designed and manufactured two new ranges of ac current transducer for permanent installation. The RCTi and RCTrms both feature a thin, clip-around coil (based on Rogowski technology) connected to a small DIN rail or panel mount electronics enclosure.
The RCTi is intended for use with oscilloscopes, data acquisition cards, power analysers and meters in power quality applications. The output from the transducer is an instantaneous voltage proportional to the measured current, and the device is seen as an ideal replacement for current transformers with medium/large ratings.
It has several advantages. Firstly, as the coil is small, lightweight and its length can be specified independently to the measured current, the product is exceptionally simple to retrofit into an existing plant. Benefits might also be gained when the current is large (above 500A), or if the current is at a high frequency or has high frequency harmonics.
Measurements in awkward locations are also simplified using the RCTi.Other advantages of the RCTi ac current transducer are its non-intrusive functionality - the current draws no power from the circuit under test - and its predictable phase response at power frequencies of 50/60Hz and above.
The device is intrinsically safe to use because there is no danger of open circuit secondaries and is not damaged by high current surges or suffer from magnetic saturation. The transducer also comes in an industrially specified version (IRF) housed in an IP65 enclosure suitable for panel mounting.
The RCTrms is a single package device that combines the benefits of a thin, flexible, clip-around Rogowski coil sensor with a signal conditioner, providing true rms measurement of ac current. It can be specified with industry standard outputs (0 to 5V or 4-20mA), making it ideal for process control or system monitoring purposes.
The RCTrms is intended for use with SCADA systems, PLCs, data loggers and protection equipment, hence typical applications include welding equipment, status alarms in production processes, large pumps and fans, current monitoring in low voltage distribution installations, and variable speed motor drives.
Features of both the RCTi and RCTrms include switch selectable dual range, traceable calibration and fully isolated measurement. The devices are available in three standard lengths of 300mm, 500mm and 700mm, and come with a 1m cable that connects to the electronic integrator. Other customised configurations are also available.