Monitor Distorted AC Current with New ATPR Series Current Transducers
NK Technologies introduces ATPR “E-Out” Series AC Current Transducers. ATPR current transducers combine a current transformer with a true RMS signal conditioner in a single package. This enables the ATPR series to produce a 0-5 or 0-10VDC RMS output on distorted waveforms located in the output of variable frequency drives, phase angle fired heating controls, and on linear loads in “noisy” power environments.
“The ATPR series provides true RMS sensing, meaning output is proportional to the current flowing in the circuit even with high distortion or harmonic loads,” says Philip Gregory, President, NK Technologies. “Field selectable ranges minimize inventory requirements and easily accomodate changes in load conditions, and a split core housing simplifies installation – users simply release the latch and snap it over the conductor. And the unit’s DC voltage output is ideal for data acquisition systems, panel meters or controllers with only voltage inputs available.”
The ATPR series is a perfect solution for monitoring the output of variable frequency driven loads, even when in bypass mode. They can also be used to measure phase angle fired heating controls and other SCR controlled loads. These current transducers respond quickly to element failure by monitoring current instead of temperature, and accurately measure power supply and ballast input power.
“Many building energy management controllers provide 0-5 VDC inputs, and many data loggers utilize 0-10 VDC inputs. ATPR series current transducers can be used in applications where the current wave is distorted or where it is sinusoidal with equal accuracy,” explains Gregory. “Even when the amount of distortion is not known users can be certain the measurement will be accurate. With this sensor the installer can use the industry standard for monitoring AC current, without having to use an external resistor that can add a degree of inaccuracy to the system.”
Engineers designing switched mode power supplies work diligently to improve pulse width modulation so the controlled load will have the cleanest power applied, reducing harmonics to reduce overheating of transformers and motors in addition to reducing zero-crossing noise. The methods for doing this are expensive, so distortion in these types of power supplies will continue for the foreseeable future. Variable speed drives, electronic ballasts, uninterruptible power supplies and other devices that use switched mode power supplies are sources of current sine wave distortion and require frequent monitoring. ATPR series current transducers are a simple and cost effective solution for monitoring distorted AC current.