Aim Dynamics: July 2014

Wednesday, July 23, 2014

What Does a DC Current Sensor Do?

DC current sensors, in simple terms, take electrical measurements in the same way a thermometer determines the temperature of an item or area. Like all other measuring devices, DC current sensors can function to make simple and complex measurements. In its most basic form, a current sensor detects electrical current in a wire and generates a signal proportional to it.

DC current sensor generated signals can be utilized to display the measured current in an ammeter or can be stored for further analysis in a database. Moreover, it can also be used for control purposes of electrical devices. As a measuring device, DC current sensors detects the current input and can come out with output signal for both unipolar and digital output types. For a unipolar output, it duplicates the wave shape of the sensed current. For a digital output, on the other hand, it changes when the sensed current exceeds a certain threshold.

DC current sensors, in some cases, can be connected directly to electrical instruments while it is more common that some signal conditioning is used. Some current-sense applications call for isolation between the DC current sense’s resistor and the measurement circuits. In such cases, isolation amplifiers and modulators may be used.

DC current measurement don’t just take place in laboratories anymore as many common devices like battery chargers have some form of current sense resistor in them. This is why knowing the basics of current sensors is important.

Wednesday, July 16, 2014

Can You Use DC on a Current Transformer?

Current transformers are a staple tool in any industry that uses electricity. Basically, a current transformer takes in a current that is too powerful and reduces it (“step down”) to a more manageable quantity. It does this by using coils or windings, with the primary one accepting the input current and the secondary winding producing the output current. Since the output current is proportional to the input one, you can easily measure the former by noting the number of coils the secondary winding has.
Of course, the type of current you introduce into the transformer plays a vital role, too. As it happens, many people wonder why you can’t use a direct current (DC) power system with transformers for power distribution.
The answer is simple: electromagnetic induction. A direct current is unidirectional, so the magnetic field it creates in the primary and secondary coils are unchanging. Unfortunately, without a changing magnetic field, electrons will not travel from one coil to the other, and thus the current cannot be “stepped down.”
What can you do to measure and reduce a direct current? One way to do this is to pulse the DC voltage supplied to the transformer. Another method is to transform the DC to an alternating current or AC. As the name suggests, an AC naturally creates a changing magnetic field, making it ideal for use with transformers.

Wednesday, July 9, 2014

Go Split Core for Easy Monitoring Maintenance

Solid core current transformers typically have a long lifespan, however, they do break down over time. When they do, it can sometimes be difficult, if not impossible, to replace them without affecting power delivery downstream.
When continuous power delivery is a must, utilizing split core CTs might be ideal. Since the rings of a split core CT can be opened up, removal and installation of the device can be achieved without having to disconnect the feeder lines they are meant to monitor.
It should be noted, however, that split core CTs do have their disadvantages over solid core CTs:
First, split core CTs are typically less accurate than solid core CTs. When accuracy is your priority, going solid core may be your only option. When faced with such a case, it may be best to incorporate a backup power supply in your design so that the main feeders can be disconnected for safe replacement of the solid core CT.
Second, split core CTs are also more expensive than solid core CTs. Some would argue, however, that in cases where a backup power supply is not a feasible option, the cost of using split core CTs can be justified by the mitigated impact to production the replacement of a CT might otherwise have.
Finally, split core CTs are bulkier than their solid core counterparts. While this might not be a problem in most cases, such aspect should be highly considered when space is at a premium.

Wednesday, July 2, 2014

A Focus on Split Core Current Transformers

Transformers are useful devices that transfer energy between two or more circuits by employing electromagnetic induction. They also come in the form of laminated core, toroidal, auto, variable, and others that are designed to serve specific functions. One of these specialized types of energy transfer devices is the split core current transformer.

Just like other types of transformers, the split core variety measures alternating current that flows through conductors, but comes with a distinguishing feature: its design. Unlike common transformers that come in a toroidal coil, the design of a split core current transformer allows it to be assembled around a buss bar without the need to disconnect the buss bar. For this unique feature, the split core type employ C-cores and U-core structures because they are built for easy dismantling and reconstruction, thereby saving time and energy.

Split core current transformers are commonly used for lower frequency applications and normally employ grain oriented silicon steel for the metal core. This type of transformer can also use nickel alloys and more exotic materials for a core to ensure less core loss at higher frequencies (typically up to about 10 kilohertz). Despite its low frequency application, the lower core loss factor makes split core types suitable for high accuracy current transformers.

Tuesday, July 1, 2014

Considerations in Choosing a Current Sensor

Whether in homes or businesses, cost is often one of the primary considerations in procuring devices,  such as a current sensor. You can certainly find products that would fit your budget, but you have to be wary of the value you get. With careful consideration, you can avoid buying inappropriate or low quality current sensors that can only result in high repair costs or inefficient outcomes.

Know the purpose for a current sensor

Current sensors can measure various energies, such as light, temperature, and magnetic fields, and convert the parameters to measurable electrical signals. Mainly used in power or instrumentation systems, this device is essential to those who wish to monitor electrical and other energy levels present in a process or situation. In industries, current sensors are typically used in batteries and chargers, voltage regulators, power-generating equipment, and other machines or electronics.

A DC current sensor is used for batteries, fuel, and solar cells, which has currents that flow in a single direction (direct current). On the other hand, an AC current sensor is commonly used in power sources that create alternating currents, which supply electricity.

Study specifications

Once you know the specific type of current sensor to acquire, pay attention to the specifications of available products. Distributors will provide comprehensive details on a product’s features and functionality. Make sure that you choose a product that complies with standards on accuracy, and which provide detailed parameters for its effective use, such as measurements, ranges, calibrations, and others.