An inquisitive child would ask a lot about what he sees around the house. While most of those questions may seem silly to adults, others simply make sense, and even make adults wonder for themselves. For instance, questions like “How does a microphone make one’s voice louder than normal?” or “Why is a flat iron hot?” can leave grownups scratching their heads. Continue reading
In days past, most current sensing designs followed only a few basic approaches. With the advancements in technology came a slew of measuring choices, making the selection process a bit more challenging. Should you choose Reflective light proximity sensors? Hall Effect sensors? How about one that uses Eddy current sensing?
Granted, for general applications, any type would likely yield satisfactory results. However, if you’re asking more from your devices, or if you have to work in extreme conditions, some options work better than others. That’s when you need to be concerned about the choices you make. Continue reading
In a production line that employs conveyors, expensive mechanical damage is often the result of the conveyor jamming but with the drive motor continuing to run. By installing a current transducer to detect an overload, the drive motor can be prevented from sustaining damages that can grind your system—and ultimately your production—to a complete halt. Continue reading
Whereas core-type current transformers have magnetic cores, flexible ones like Rogowski coils don’t have any. A Rogowski coil’s shell only houses a helical coil wire whose ends are located at the attachable terminals. If a Rogowski coil had a magnet inside, it would lose its flexibility due to the solid slab of magnetic material.
Instead, it relies on the electromagnetic field the conductor itself generates, which simply refers to the metal conduit. Flexible transformers rely on Ampere’s law to pick up the electromagnetic field looping around the wire. According to the law, current movement along this imaginary loop is the same as current movement along the conduit. Continue reading
Current transformers are rated at both primary and secondary windings. In a standard setup, the primary winding consists of the conductor passing through the transformer, while the secondary winding has the coil around the core hooked to a metering device like an ammeter. Consequently, a transformer with a 100/5 spec means the primary current is at 100 A, while the secondary current is at 5 A.
The use of the term “windings” is universal for both current transformers and transformers in general. However, current transformers are more concerned with measurement than stepping voltages up or down (although they have this capability, to some extent). The primary current is current from a power source, while the secondary current delivers the power to the load (i.e. ammeter). Continue reading
Like any other device, current sensors and transformers must have at least one ground, namely in low-voltage circuits (below 1,000 volts). Although most systems are protected against sudden surges, it pays to add extra insurance to ensure the safety of the circuit, be it a solid-core, split-core, or Rogowski coil.
Grounding attaches a less-resistant conduit to the earth to provide as a return line for an excess charge, particularly one provided by lightning. Electricity follows the path of least resistance, so a ground connection can keep devices working and save lives. The earth is a poor conductor of electricity, after all, making it a suitable detour for excess voltage. Continue reading
Solid and split-core current transformers and transducers work like a charm, but their rigidness may not work to the benefit of some circuits. Solid-core CTs are just as they appear—solid slabs that require shutting the power down to enable safe installation. Split-core CTs don’t require this step but can eat up a lot of space in the circuitry.
Fortunately, flexibility and versatility come in the form of a third type of CT: the Rogowski coil. Named after German physicist Walter Rogowski, the coil features the accuracy of a solid-core CT and the ease of installation of a split-core CT, yet works the same way as the two. Inside its colored tubes is a helical ring that responds to the conductor’s electromagnetic field. Continue reading