What are Linear Image Sensors?

Fairchild Imaging makes CMOS 1421, a linear image sensor. This is an imaging device with a wide dynamic range of 94 dB or 52000:1, with excellent linearity. The device is a linear sensor, meaning it has 2048 x 1 high-resolution imaging sensors. Fairchild has designed this linear sensor for medical and scientific line scan applications such as optical inspection or fluorescent imaging that require wide dynamic range, high sensitivity, and low noise operation.

With several acquisition modes, this photodiode pixel has an optical area measuring 7 x 10 µm with a pitch of 7 µm and a fill factor of 85%, making the operation of this sensor very flexible:

  • Read after Integration: This mode is ideal for applications with high quality signals
  • Buffered Read after Integration: is a high speed mode that integrates the next line while reading the current line
  • Read on Integration: This is a non-CDS mode, allowing the highest speed of operation
  • Multiple Read during Integration: This mode is for low-light applications, permitting oversampling during integration

Other than the above, a programmed mode, accessible through JTAG interface, meets a wide range of specialized imaging requirements. Readout cycles in this mode are controllable through external signals.

CMOS 1421 has several features such as very low dark current, very low readout noise, and non-destructive readout for fowler sampling. Along with anti-blooming drain and electronic shutter, the CMOS 1421 also features two independent gain settings for each pixel. The entire device is enclosed in an RoHS compliant CLCC and PLCC package of 22.35 x 6.35 x 2.85 mm dimensions. The device consumes 40 mW of power while operating from 3.3 VDC. Major applications of linear image sensors are in microscopy, photon counting, and fluorescent imaging.

CMOS 1421 has a pixel array consisting of a photodiode, a pixel amplifier, and a sample and hold circuit. Along with the above, each pixel has a noise suppression circuitry and a gain register. While the pixel-level gain affects the device sensitivity, it also has a bearing on the noise and conversion factor of the sensor.

Linear image sensors from Fairchild use thinned back-illuminated large area arrays. Fairchild offers custom capabilities such as extreme spectral band detection, low noise active reset CMOS architecture, and high-resolution X-ray imagery using these sensors.

These linear image sensors are ideal for visible, ultra violet to visible, and visible to near infrared spectrometers, and their enhancement makes them suitable for spectroscopy applications. The design of their pixels being tall and narrow helps light distribution from a spectrometer’s grating. If provided with UV sensitivity, these sensors do not need extra UV coating.

CMOS 1421 displays superior linearity, which is of extreme benefit to spectroscopy measurements. The device also includes an electronic shutter along with a built-in timing generator, which are useful in spectroscopy. The device is suitable for several applications involving scientific, industrial, and commercial activities.

New sensors based on CMOS match features with those of CCDs. Featuring simpler external circuit design, and simpler operation, CMOS 1421 linear image sensors are suitable for spectroscopy, displacement measurement, barcode scanning, and imaging.

What are 3-D Image Sensors?

3-D image sensors from Infineon are perfect for use in mobile consumer devices. These new REAL3 image sensors measure the time-of-flight of infrared signals, enabling sensing gestures the user makes in front of the screen. Infineon has designed the sensors with a perfect combination of power consumption, performance, functionality, cost, and size. The IRS238xC 3-D image sensors work in any kind of ambient light conditions and this makes them indispensable for reliable use in mobile applications.

The IRS238xC has high-performance pixel arrays that are highly sensitive to infrared light of 850 and 940 nm wavelength. This allows the device to perform unparalleled in any outdoor environment. Combined with this, Infineon has provided its patented SBI or suppression of background illumination circuitry in every pixel. The combination extends the nominal dynamic range of each pixel by nearly 20 times.

As the single-chip design has a high integration level, it allows the user to optimize the bill of material. Apart from this, it also reduces the design complexity and offers a small form factor. There are other advanced features as well, such as integrated high-performance ADCs, illumination control logic, a modulation unit with high flexibility, and circuitry for eye-safety that enables it to work as a laser-class-1 device. Interfacing is through a high-speed CSI-2 data interface.

The IRS238xC operates from an optimized in-built voltage supply unit, and it can self-boot as it has a full SPI master memory interface. Among the new features available on the sensor are, coded modulation and enhanced configuration flexibility. This allows the device to perform flexibly and robustly in multi-camera scenarios and similar use-cases.

The time of flight technology from Infineon works with stability, as high assembly yields prove, and this is a great boon for camera module manufacturers, as the IRS238xC not only simplifies calibration efforts, it also simplifies the camera module design. In short, IRS238xC combines the benefits of reliability, cost, size, functionality, and power consumption, making it indispensable for mobile 3-D sensing applications in all kinds of ambient light conditions.

For instance, the IRS238xC has the smallest module size giving 224 x 172 pixels, each of size 14 µm and with their own individual micro-lens. The suppression of background illumination or SBI provides each pixel with a 20-time gain in dynamic expansion against strong sunlight, but at minimum power consumption. The robust high-volume assembly of the device and its low calibration efforts offer an easy design and low system bill of materials for the designer.

IRS238xC offers time-of-flight technology for directly measuring the amplitude and depth of information in every pixel. It does this using a single modulated infrared light source that the chip emits to the whole scenery. The TOF imager captures the reflected light. The unit measures the phase difference between the emitted and the reflected light along with their amplitude values, thereby calculating the distance information and producing a grayscale picture of the entire scene all in one sweep.

Infineon provides algorithms that feature unique multiple benefits compared to other depth sensing technologies such as stereovision or structured light.

Making a PiPlateBot with the Raspberry Pi

Turtle robots of the yesteryears had always fascinated Robert Doerr and he decided to create one with the popular single board computer, the raspberry Pi or RBPi. He hid all components of the robot inside the plate case, and decided to call his robot PiPlateBot.

Robert Doerr is the owner of Robot Workshop, and a dedicated robot builder. He used the Bud Pi Plate case, as this was strikingly similar to the turtle-style robots computer science students used earlier.

The Pi Plate has a circular design. Twisting off the top allows easy access to the space within that can house additional components. That led Robert try to fit an RBPi inside, along with the other parts required to build a moving robot. According to Robert, the PiPlateBot is the only robot that runs on an RBPi and uses an off the shelf RBPi case. Robert claims he is using as many RBPi-type products as possible for the construction.

To get everything to fit, Robert had to cut two rectangular holes in the Pl Plate enclosure base. Then he glued servos to the bottom and clipped the RBPi and RoboPi boards on the top. On the boards, he placed a BZO power bank to work as a battery. To enable communicating wirelessly with the RBPi, Robert uses a USB Wi-Fi adaptor. This allows him to SSH directly into the RBPi.

The RoboPi is an impressive motor controller, and the most powerful one for the RBPi. Using an eight-core 32-bit Parallax Propeller RISC micro-controller at 100 MHz, it allows offloading hard real time IO from the Linux OS running on the RBPi, thereby giving timing with greater precision to projects. The RoboPi will work with any RBPi model.

Each core on the RISC controller works at 25 MIPS, with each instruction taking only four clock cycles to complete. The RoboPi has three ten-pin IO module expansion connectors and they provide 24 servo-compatible headers. Some of these connectors use jumper selectable power from the internal 5 VDC or the external servo power supply for powering the sensors.

The user can connect servos to screw terminals that provide external power. There are eight headers for setting up an eight channel 0-5 V analog to digital converter. The user has a choice of using MCP3008 for 10-bit AD conversion or MCP3208 for 12-bit AD conversion.

Therefore, while the RBPi does the high-level thinking, the Parallax Propeller chip on the RoboPi board handles all the IO controlling and the real-time tasks. As the RoboPi controller has both C and Python libraries, Robert plans to write a Logo Interpreter to make the PiPlateBot use Logo to emulate the early turtle robots.

As the PiPlateBot has only two servos controlling its two wheels, the robot actually wobbles when operated. Robert had to use furniture gliders to prevent this. He attached them to the front and rear of the PiPlateBot. A sonar sensor fitted on the PiPlateBot allows it to sense its surroundings.

Building a robot is the fun way of learning to use the RBPi, and a great way to learn programming on the SBC.

What are Laminated Bus Bars?

Rather than use one solid bar of copper, the industry prefers laminated bus bars. These are fabricated components with layers of engineered copper bars separated by flat dielectric materials, bound together into a unified construction. Laminated bus bars offer several advantages—improved reliability and reduced system costs. They are available in various sizes and shapes, some as big as a fingertip while others more than twenty feet in length. Several industries use multilayered bus bar solutions routinely and they include telecommunications, computers, industrial, military, transportation, alternative energy, power electronics, and many more.

Laminated bus bars are good for reducing the system costs, improving system reliability, increasing capacitance, lowering inductance, and eliminating wiring errors. Additionally, the physical structure of the bus bars also acts as structural members of a complete power distribution subsystem. Multilayer bus bars function as a structural integration that other wiring methods cannot match.

The decreased assembly time and the internal material handling costs for laminated bus bars bring down the overall manufacturing costs. Assembly operating procedures can be difficult to follow and assemblers often resort to guesswork, leading to wiring errors. Using laminated bus bars eliminates this totally, as installers have to terminate various conductors at specified locations. Not only does this reduce the parts count, it also reduces ordering, inventory costs, and material handling.

Fabricators can make laminated bus bars fit specific needs and customize them for maximizing efficiency. The use of laminated bus bars, therefore, helps the organization build quality into processes. With reductions in wiring errors, the organization has fewer reworks, and they can lower their quality and service costs.

Laminated bus bars offer increased capacitance and lower inductance, resulting in lower characteristic impedance. The benefit to the industry is greater noise cancellation and effective noise suppression. Manufacturers can control the capacitance by using dielectrics of various thicknesses and different relative K factor.

Multilayered bus bars can replace cable harnesses—this eliminates mistakes in wirings. Moreover, failure rate of bus bars is extremely low, while wiring harnesses fail very often. That makes repairing and or replacing wire harnesses an expensive process, while using bus bars in the system is adding an effective insurance.

According to physics, a conductor carrying current develops an electromagnetic field around the conductor. As laminated bus bars have thin parallel conductors with thin dielectric material separating them, the effect of inductance on electrical circuits is a minimum. With opposing potentials laminated together, the magnetic flux cancellation reaches a maximum. Semiconductor applications routinely use laminated bus bars to reduce the proximity effect. GaN and or SiC high frequency circuits also use laminated bus bars to reduce high electromagnetic interference.

Using wide and thin conductors and laminating them together to form bus bars actually decreases the space requirement, thereby allowing a better airflow in systems and improving system thermal characteristics. Moreover, the flexibility of these bus bars provides the industry with a wide variety of interconnecting methods. Assemblers commonly use tabs, embossments, and bushings for installing laminated bus bars. Manufacturers also offer pressed-in fittings that can integrate into the design. This makes laminated bus bars compatible with almost any type of interface.

What is a PCB Via and How is it Made?

Vias are actually holes drilled into PCB layers and electroplated with a thin layer of copper to provide the necessary electrical connectivity. Three most common types of plated through via are in use—plated through holes, blind holes, and buried holes—with plated through holes running through all the layers of the PCB. These are the simplest type of holes to make and the cheapest. However, they take up a huge amount of PCB space, reducing the space available for routing.

Blind vias connect the outermost circuit on the PCB with other circuits on one or more adjacent inner layers. As they do not traverse the entire thickness of the PCB, they increase the space utilization by leaving more space for routing.

Buried vias connect two or more circuit layers in a multi-layered PCB, but do not show up on any of the outer layers. These are the most expensive type of vias and take more time to implement, as the fabricator has to drill the hole in the individual circuit layer when bonding it. However, designers can stack several buried vias in-line or in a staggered manner to make a blind via. Therefore, buried vias offer the maximum space utilization when routing a PCB. Fabricators of high-density interconnect (HDI) boards usually make use of buried vias, most often using lasers for drilling them.

Drilling a Via

At positions for the vias, the fabricator drills holes through the PCB using a metal drill of small diameter. He or she then cleans the hole, de-smears it, and de-burrs it to prepare it for plating. Rather than removing copper as is normally the case with the etching process, the fabricator then adds a thin layer of copper to the newly formed hole through a process of electroplating, thereby connecting the two layers. For a two-layer board, the fabricator then etches circuit patterns on both sides. Via usually have capture pads on both layers.

The process of drilling a via hole using a laser is somewhat different. In general, fabricators use two types of lasers—CO2 and UV—with the latter able to make very small diameter via holes. UV laser-drilled via holes are about 20-35 µm in diameter. As the laser beam is able to ablate through the thin copper layer, capture pads with a central opening are not necessary. Most fabricators program a two-step process for drilling a hole with a laser beam.

In the first step, a wider-focused laser heats the top copper layer, driving the metal rapidly through the melt phase into the vapor phase prior to gas-dynamic effects expelling it from the surface. The laser repeats this for all via positions on the PCB layer.

In the next step, the program focuses the beam tightly and controls the depth the laser can burn. For blind vias, It allows the laser to burn through the intervening dielectric and stop when it has reached the bottom copper layer, before moving on to the neighboring via position.

The same process of electroplating as above deposits a thin layer of copper along the walls of the holes left behind by the laser beam, thereby connecting the two layers. The rest of the process for etching the circuit pattern on the two sides remains the same.

How useful are PCB Vias?

Designers use a plated through via as a conduit for transferring signals and power from one layer to another in a multi-layer printed circuit board (PCB). For the PCB fabricator, the plated through via are a cost-effective process for producing PCBs. Therefore, vias are one of the key drivers of the PCB manufacturing industry.

Use of Vias

Apart from simply connecting two or more copper layers, vias are useful for creating very dense boards for special IC packages, especially the fine-pitch components such as BGAs. BGAs with pitch lower than 0.5 mm usually do not leave much space for routing traces between neighboring pads. Designers resort to via-in-pads for breaking out such closely spaced BGA pins.

To prevent solder wicking into the via hole while soldering and leaving the joint bereft of solder, the fabricator has to fill or plug the via. Filling a via is usually with a mixture of epoxy and a conductive material, mostly copper, but the fabricator may also use other metals such as silver, gold, aluminum, tin, or a combination of them. Filling has an additional advantage of increasing the thermal conductivity of the via, useful when multiple filled vias have to remove heat from one layer to another. However, the process of filling a via is expensive.

Plugging a via is a less expensive way, especially when an increase in thermal conductivity does not serve additional value. The fabricator fills the via with solder mask of low-viscosity or a resin type material similar to the laminate. As this plugging protects the copper in the via, no other surface finish is necessary. For both, filled and plugged vias, it is important to use material with CTE matching the board material.

Depending on the application, fabricators may simply tent a via, covering it with solder mask, without filling it. They may have to leave a small hole at the top to allow the via to breathe, as air trapped inside will try to escape during soldering.

Trouble with Vias

The most common defect with vias is plating voids. The electro-deposition process for plating the via wall with a layer of copper can result in voids, gaps, or holes in the plating. The imperfection in the via may limit the amount of current it can transfer, and in worst case, may not transfer at all, if the plating is non-continuous. Usually, an electrical test by the fabricator is necessary to establish all vias are properly functioning.

Another defect is the mismatch of CTE between the copper and the dielectric material. As temperatures rise, the dielectric material may expand faster than the copper tube can, thereby parting the tube and breaking its electrical continuity. Therefore, it is very important for the fabricator to select a dielectric material with a CTE as close as possible to copper.

Vias placed in the flexing area of a flex PCB can separate from the prepreg causing a pad lift and an electrical discontinuity. It is important designers take care to not place any vias in the area where they plan the PCB will flex.

HiFiBerry & Raspberry Pi Put New Life into Old Loudspeakers

If you have some old stereo speakers stored away in your basement, chances are they connect through the old way—with wires—to an amplifier, and that is the reason they were banished to the basement. With HiFiBerry Amp+ and a single board computer, such as the Raspberry Pi (RBPi), you can resurrect your vintage speakers. Using the latest in open source technology, you can now use the renovated loudspeakers wherever you want, since they now operate wirelessly.

HiFiBerry offers their Amp+ as an amplifier for the RBPi. As it is a Class-D power amplifier, it is highly efficient as a stereo module, and you only need to connect the loudspeakers. This high-quality amplifier is ideal for setting up multi-room audio installations.

The amplifier is stable enough to drive 4-Ohm loudspeakers and those with higher impedance as well, pumping out 25 W of output power. However, the best part is the RBPi can fully control the amplifier. As the amplifier includes on-board digital to analog converters, you do not need external sound cards or DACs to provide the 44.1 KHz and 48 KHz sample rates. The board connects directly to the RBPi without needing additional cables, and this provides a full digital sound path for optimal audio performance.

The HiFiBerry Amp+ comes as a pre-fabricated kit, so it needs no soldering. It is a daughter board for the RBPi, and when the RBPi plugs into it, you need to connect only a single external power supply of 12-18 V to supply both the amplifier and the SBC, as the RBPi draws power from the Amp+. You can use the Amp+ with all RBPi models that have the 40-pin GPIO connector. The board sits on four small plastic spacers that come with the kit.

The specialty of the Amp+ kit is it converts the digital signal into audio with far greater clarity than the RBPi can, and delivers that to the speaker as a 25 W audio amplifier. On the reverse side of the board, the female connector is easily visible, so it is easy to plug in the GPIO pins of the RBPi.

On one side of the board are a jack for powering the board, and six wire-terminals. If for some reason you cannot use the jack to power the board, use the two wire-terminals on the left. The rest of the four wire-terminals are for connecting to a pair of stereo loudspeakers, using two audio cables per speaker.

As the board takes in 12-18 V supply and delivers power to the RBPi as well, it is important to not power the RBPi from its usual 5 V power supply. This reduces the number of wires to the assembly. As the Amp+ board is very small, it does not protrude beyond the RBPi. It is important to mount the board on the four plastic spacers to avoid breaking the GPIO pins.

The SD card for the RBPi can be of the 8 GB type and people have reported better performance with Transcend cards. However, you can use 16 GB cards as well.

Are Ferrites Good for Interference Suppression?

Although ferrite beads and sleeves are a common sight on cables, the technique for reducing both outgoing and incoming RF interference is the least understood. To study ferrites, and to do some comparative frequency domain measurements, one needs actual ferrite samples, a specially designed test jig, a spectrum analyzer, and a tracking generator.

Any current flowing through a metal conductor will create a magnetic field around it. The inductance of the conductor transfers the energy between the current and the magnetic field. A straight wire has a self-inductance of about 20 nH per inch. Any magnetically permeable material placed around the conductor helps to increase the flux density for a given field strength, thereby increasing the inductance.

Ferrite is a magnetically permeable material, and the composition of the different oxides making it up control its permeability, which is frequency dependent. The composition is mainly ferric oxide, along with nickel and zinc oxides. Furthermore, the permeability is complex with both real and imaginary parts. Therefore, the line passing through the ferrite has both inductive and resistive components added to the impedance.

The ratio of these components varies with frequency. The resistive part dominates at higher frequencies, and the ferrite behaves as a frequency dependent resistor. Therefore, the assembly shows loss at high frequencies, with the RF energy dissipating in the bulk of the material. At the same time, there are few or no resonances with stray capacitances.

Cables are usually in the form of a conductor pair, carrying signal and return, or power and return. Multi-way cables may carry several such pairs. The equal and opposite return current in each circuit pair usually cancels the magnetic field from the current in the forward line. Therefore, any ferrite sleeve place around a whole cable will have zero effect on the differential mode currents in the cable. This is true as long as the sum of differential-mode currents in the cable is zero.

However, for currents in the cable in common mode, with conductors carrying current in the same direction, the picture is different. Usually, such cables produce ground-referred noise at the point of connection or have an imbalance of the impedance to ground, causing a part of the signal current returning to ground through paths other than through the cable.

For instance, a screened cable, improperly terminated, may carry common-mode currents. As their return paths are essentially uncontrolled, these currents have a great potential for interference, despite being of low levels. Sometimes, the incoming RF currents, although generated in common mode, convert to differential mode and so affect circuit operation. This happens due to differing impedances at the cable interface.

As common mode currents in a cable generate a magnetic field around it, placing a ferrite sleeve around the cable increases the local impedance of the cable and operates between the source and load impedances.

When interfacing cables, low source impedance implies the ferrite sleeve is most effective when adjacent to a capacitive filter to ground. Since the length and layout of a cable will usually vary, engineers take the average value of the cable impedance as 150 ohms.

How do Antistatic Bags Work?

Computer boards and sensitive electronic components need protection from electrostatic discharge, especially at the time of shipping, handling, and assembly. This requirement has led to the development of an entirely new class of antistatic packaging materials. Now, a multi-million dollar packaging industry exists, with major developments in polymers. These are special conductive polyethylene and other laminates covered with very thin metalized films. This packaging industry saves several hundred million dollars each year for the computer and electronic industry, dwarfing almost all other industrial and commercial antistatic abatement enterprises.

To demonstrate the working of an antistatic bag that store and ship assembled boards and electronic components, one needs an apparatus including a tonal electrostatic voltmeter or TESV, several antistatic bags big enough to cover the TESV mounted on a tripod, a plastic tube or rod, and a rubbing cloth. Wool or silk cloth will work well with a Teflon, Nylon, or PVC pipe.

To disallow any movement of the TESV when operating, mount the instrument on a tripod, turn it on, and zero the instrument. Now charge a plastic rod by rubbing it with the cloth, and bring it close to the sensing head of the TESV. The instrument will respond by indicating the presence of electrostatic charge.

Covering the TESV with one of the antistatic bags shows it now registers little or no charge when repeating the experiment. Even with the charged conducting object discharging directly to the bag, the TESV shows little or no charge indication. The only possible explanation is the conductive bag shields the TESV from the electrostatic field.

The bag shields the instrument even though it is not connected to ground. If it were necessary to ground the bag to make it work, the antistatic bag would have been more inconvenient and ineffective than they are now. Grounding is not necessary here as electric charge resides only on the outer surface and does not penetrate inside, or into any void enclosed by the conductive material. The ungrounded bag simply holds the charge harmlessly only on the outside.

This also solves the problem of removing a sensitive component from inside the bag. When a person handles the bag, the contact with the hand grounds the bag and drains the charge from its surface. However, if the person were wearing an insulated glove, the component would draw a strong electric spark when it is withdrawn from the bag, and may be damaged.

Antistatic and static shielding materials are commercially available for every size and shape necessary. Specifications usually refer to MIL standards or the rate of charge dissipation, along with abrasion resistance, thickness, and others. Some advertisers refer to their antistatic bags as Faraday cages, since it does not allow charge to penetrate inside the bag.

Another type of antistatic bag has no metal layer, but is actually a bag made of a conductive polyethylene film. The manufacturer claims the bag can dissipate 5 KV in 2 seconds. Although in practice it is the electric charge that dissipates, the voltage is far easier and more convenient to monitor, and is directly proportional to the charge for a fixed capacitance geometry.

Problems Mains Harmonics Cause

Single-phase power converters are specifically problematic since they generate significant levels of triplen harmonics, such as the 3rd, 9th, 15th, etc. As they do not undergo phase cancellation, they add up linearly in the neutral conductor to create a particular nuisance. Apart from this, they are also present in zero-phase transformer flux, and heat up cables and transformers. Although three-phase converters also generate harmonic emissions, the triplen currents produced by them are of much lower levels.

Other non-linear loads also contribute to harmonic currents in the mains supply. Such loads include motors and transformers, welding equipment and arc furnace rectifiers. Another source is the fluorescent lamp with magnetic ballast. However, rectifiers produce much higher frequencies as compared to that from fluorescent lamps.

The harmonic currents an equipment draws from the AC mains supply do not alter the power the equipment consumes when measured in Watts. However, the harmonic currents increase the VA rating of the equipment. Since Power Factor is the ratio of the Watts to the VA the equipment consumes, the equipment that produces significant emissions of harmonics also has a lower power factor.

A resistive load, such as an incandescent lamp, has a PF of 1.0 since it consumes the same amount of power in Watts, as it does in VA. Therefore, an incandescent lamp cannot emit any harmonic content. On the other hand, electronic equipment with rectifiers at the input and with no harmonic reduction techniques have power factors of around 0.6, implying they generate harmonic currents. Fluorescent lamps with magnetic ballast, running at 50/60 Hz, usually have PF of the order of 0.3, so they generate significant amounts of triplen harmonics.

The power factor of the load is significantly different from the power factor traditional electrical generation and distribution engineers use—the latter is the cosine of the angle between the sine-wave supply voltage and its load current. While the traditional PF assumes all loads are linear using sine wave voltages, engineers adjust this PF by adding capacitance or inductance to the power line, depending on whether the load is resistive, inductive, or capacitive.

However, the traditional method of PF correction for linear loads fails when trying to correct the PF of a rectifier-input electronic power converter. Mains power distribution networks are now driving significant numbers of electronic loads as these operate at higher efficiencies, and electronic loads are now replacing most linear loads.

The standard IEC 61000-4-7 [6] offers a survey of harmonics present in power supply systems. Typically, there are four major kinds of problems that harmonic currents cause when they are flowing in mains power supply networks:

  • Problems that harmonic currents themselves cause
  • Voltage distortion from harmonic currents
  • Problems that voltage distortions cause
  • Interference to telecommunication networks

In large installations with several single-phase electronic loads, such as in modern offices, the total neutral currents may reach as high as 1.7 times the highest phase current. This is the effect of harmonic currents, mainly the triplens, as these flow without being cancelled, in the neutral conductor. As many older buildings have half-sized or even smaller diameter neutrals, there can be a risk of fire hazard.