Category Archives: Newsworthy

3-D Electrodes in Solid-State Batteries

Addionics is an Israeli startup in the rechargeable business. It is recently engaging in redesigning the battery architecture with respect to its electrode technology. The company wants to replace the regular 2-D electrode layer structure in traditional batteries. They want to integrate a 3-D electrode structure. They claim this will provide greater power and energy density, while also extending the life of the battery.

Addionics has five commercial projects lined up. They are presently targeting automotive applications with leading suppliers. The aim of each of these projects is to focus on different battery chemistries and integrate them with the smart 3-D electrode structure. The chemistries they are targeting are solid-state batteries, lithium polymer batteries, silicon anode batteries, lithium iron phosphate batteries, and lithium nickel manganese cobalt oxide batteries.

With the global economy striving towards electrification due to rising greenhouse gas emissions and climate change, the need for replacing renewable energy use, energy storage, and EV adoption is increasing. However, this can succeed only if there are batteries available that are more efficient, safe, and cost-effective.

Scientists all over are devoting huge efforts and expenditures to developing the next generation of batteries. They typically focus on battery chemistry, new chemicals, and unique chemical formulations. This includes lithium-metal and lithium-sulfur.

They are also trying to make current batteries either store more energy or charge/discharge at a faster rate. However, current batteries available in the marketplace today do not have the capacity to deliver both quick charging and extended range for EV applications.

There is also a challenging mismatch between the anode and cathode in current batteries. Addionics is striving to improve battery performance with their technology. They claim their 3-D electrode technology will improve battery performance irrespective of battery chemistry, and do so without increasing the battery price.

Although solid-state batteries hold plenty of promises, their major problem is the mismatch in the anode and cathode capacity. The new technology from Addionics has the advantage of not only solving the electrode mismatch but also providing a solid-state battery with higher energy and more stable performance.

Traditionally, battery electrodes are a 2-dimensional structure, made of dense metal foils with the active material as a layer on the top. However, this 30-year-old design is no longer able to meet the growing demands of performance.

The new 3-D electrode structure lowers the internal resistance of the battery, even at higher loads, as it has the active material integrated throughout the electrode. This increases the active surface area of the battery cell architecture and improves the properties of the electrodes, leading to lower heat generation, less material expansion, improved conductivity, and enhanced energy density in the battery.

The company claims that its new 3-D electrode technology offers significant advantages for any existing or emerging battery chemistry. They claim their new electrodes can reduce the charging time, extend its drive range, and improve the safety and lifetime of the battery. Moreover, the new electrodes do not change the battery size or its components. They also claim their new technology significantly lowers the manufacturing costs of any battery, irrespective of the battery chemistry.

Anechoic Chambers for RF and Electromagnetic Testing

As the meaning of anechoic is ‘without echo’, an anechoic chamber represents a room that has minimal wave reflections from the floor, ceiling, and walls. Anechoic chambers are, therefore, suitable for testing Radio Frequency or RF, electromagnetic interference or EMI, and electromagnetic compatibility or EMC. Special materials on the floor, ceiling, and walls of the chamber help to absorb electromagnetic waves.

Another type of anechoic chamber is suitable for audio waves. The design of such chambers is meant for testing audio recording. The floor, ceiling, and walls have special material and their design helps to absorb sound waves.

A wide range of application areas requires accurate measurements of the electromagnetic spectra. For instance, the testing of an antenna requires measuring the electromagnetic energy levels that it is sending or receiving in all directions. Engineers call this the radiation pattern of the antenna, and the pattern can be in three dimensions, or in the principal plane.

When testing an antenna in an anechoic chamber, engineers use a reference antenna for transmitting a known level of power. They rotate the antenna under test to a known angle and allow the measurement system to record the power it receives. By rotating the position of the antenna under test to a different angle, they can take another measurement of the power it is now receiving. By combining all the measurements, they can form a polar plot representing the radiation pattern in that elevation or azimuthal plane.   

Conducting this exercise in the open area test site offers several disadvantages.

The test environment may have extraneous electromagnetic waves that the antenna can pick up along with the test signal. This will introduce errors in the measurement. A variety of sources can supply these extraneous waves, including air traffic, cell phones, FM radio transmitters, and more.

Moreover, weather conditions like rain and wind may also easily affect outdoor measurements of electromagnetic radiation.

Additionally, there can be reflections from nearby structures and the floor. The antenna under test will likely pick up these unwanted reflections as well.

Testing inside an anechoic chamber helps engineers avoid the above disadvantages. Typically, anechoic chambers use metal walls as a shield for preventing external radio signals from impinging on equipment inside the chamber. Special RF absorbing materials on the interior walls, floor, and ceiling of the chamber help in absorbing unwanted reflections of radio waves.

In fact, a shielded and non-reflecting anechoic chamber represents an infinitely large room, where the reflections do not reach the device under test, thereby enabling repeatable and accurate measurements.

Available anechoic chambers range in size from a typical room to a small tabletop enclosure. In fact, some anechoic chambers are so big engineers can easily walk inside, while some are as large as an aircraft hangar.

Pyramidal foams with a loading of conductive carbon often cover the internal surfaces of anechoic chambers. The tapered structure of the pyramidal shapes ensures minimal wave reflections for radio waves hitting them, while the presence of conductive carbon helps to absorb the waves. The RF absorbing material converts the absorbed incident electromagnetic energy to heat.

Double-Sided Cooling for MOSFETs

Emission regulations for the automotive industry are increasingly tightening. To meet these demands, the industry is moving rapidly towards the electrification of vehicles. Primarily, they are making use of batteries and electric motors for the purpose. However, they also must use power electronics for controlling the performance of hybrid and electric vehicles.

In this context, European companies are leading the way with their innovative technologies. This is especially so in the development of power components and modules, and specifically in the compound semiconductor materials field.

ICs used for handling electrical power are now increasingly using gallium nitride (GaN) and silicon carbide (SiC). Most of these devices are wide-bandwidth devices, and work at high temperatures and voltages, but with the high efficiency that is typically demanded of them in automotive applications.

Silicon Carbide is particularly appealing to the automotive industry because of its physical properties. While silicon can withstand an electrical field of 0.3 MV/cm before it breaks down, SiC can withstand 2.8 MV/cm. Additionally, SiC offers an internal resistance 100 times lower than that of silicon. These parameters imply that a smaller chip of SiC can handle the same level of current while operating at a higher voltage level. This allows smaller systems if made of SiC.

Apart from functioning more efficiently at elevated temperatures, a full SiC MOSFET module can reduce switching losses by 64%, when operating at a chip temperature of 125 °C. Power control units for controlling traction motors in hybrid electric vehicles must operate from engine compartments, and this places additional thermal loads on them.

Manufacturers are now exploring various solutions for improving the efficiency, durability, and reliability of SiC MOSFETs under the above operating conditions. One of these is to reduce the amount of wire bonding by using double-sided cooling structures. This cools the power semiconductor chips more effectively. Therefore, overmolded modules with double side cooling are rapidly becoming more popular, especially for mid-power and low-cost applications.

As a result of the research at the North Carolina State University, researchers have developed a prototype inverter using SiC MOSFETs that can transfer 99% of the input energy to the motor. This is about 2% higher than silicon-based inverters under regular conditions.

While an electric vehicle could achieve only 4.1 kW/L in the year 2010, new SiC-based inverters can deliver about 12.1 kW/L of power. This is very close to the goal of 13.4 kW/L that the US Department of Energy has set for inverters to be achieved by 2020.

With the new power component using double-sided cooling, it is capable of dissipating more heat effectively in comparison to earlier versions. These double-sided air-cooled inverters can operate up to 35 kW, easily eliminating the need for heavy and bulky liquid cooling systems.

The power modules use FREEDM Power Chip on Bus MOSFET devices to reduce parasitic inductance. The integrated power interconnect structure helps achieve this. With the power chips attached directly to the busbar, their thermal performance improves further. Air, as dielectric fluid, provides the necessary electrical isolation, while the busbar also doubles as an integrated heatsink. Thermal resistance for the power module can reach about 0.5 °C/w.

Smart Batteries with Sensors

Quick-charging batteries are in vogue now. Consumers are demanding more compact, quick-charging, lightweight, and high-energy-density batteries for all types of electronic devices including high-efficiency vehicles. Whatever be the working conditions, even during a catastrophe, batteries must be safe. Of late, the Lithium-ion battery technology has gained traction among designers and engineers as it satisfies several demands of consumers, while at the same time being cost-efficient. However, with designers pushing the limits of Li-ion battery technology capabilities, several of these requirements are now conflicting with one another.

While charging and discharging a Li-ion battery, many changes take place in it, like in the mechanics of its internal components, in its electrochemistry, and its internal temperature. The dynamics of these changes also affect the pressure in its interface within the housing of the battery. Over time, these changes affect the performance of the battery, and in extreme cases, can lead to reactions that are potentially dangerous.

Battery designers are now moving towards smart batteries with built-in sensors. They are using piezoresistive force and pressure sensors for analyzing the effects charging and discharging have on the batteries in the long run. They are also embedding these sensors within the battery housing to help alert users to potential battery failures. Designers are using thin, flexible, piezoresistive sensors for capturing relative changes in pressure and force.

Piezoresistive sensors are made of semi-conductive material sandwiched between two thin, flexible polyester films. These are passive elements acting as force-sensitive resistors within an electrical circuit. With no force or pressure applied, the sensors show a high resistance, which drops when the sensor has a load. With respect to conductance, the response to a force is a linear one as long as the force is within the range of the sensor’s capabilities. Designers arrange a network of sensors in the form of a matrix.

When two surfaces press on the matrix sensor, it sends analog signals to the electronics, which converts it into a digital signal. The software displays this signal in real-time to offer the activity occurring across the sensing area. The user can thereby track the force, locate the region undergoing peak pressure, and identify the exact moment of pressure changes.

The matrix sensors offer several advantages. These include about 2000-16000 sensing nodes, element spacing as low as 0.64 mm, capable of measuring pressure up to 25,000 psi, temperature up to 200 °C, and scanning speeds up to 20 kHz.

Designers also use single-point piezoresistive force sensors for measuring force within a single sensing area. They integrate such sensors with the battery as they are thin and flexible, and they can also function as a feedback system for an operational amplifier circuit in the form of a voltage divider. Depending on the circuit design, the user can adjust the force range of the sensor by changing its drive voltage and the resistance of the feedback. This allows the user complete control over measuring parameters like maximum force range, and the measurement resolution within the range. As piezoresistive force sensors are passive devices with linear response, they do not require complicated electronics and work with minimum filtering.

Power Transmission Through Lasers

Wireless power transfer has considerable advantages. The absence of transmission towers, overhead cables, and underground cables is the foremost among them, not to exclude the expenses saved in their installation, upkeep, and maintenance. However, one of the major hurdles to wireless power transmission is the range it can cover. But now, Ericsson and PowerLight Technologies have provided a new proof of concept project that uses a laser beam to transmit power optically to a portable 5G base station.

Wireless power transmission is not a new subject to many. People use wireless power for charging many devices like earbuds, watches, and phones. But the range in these chargers is short, as the user must place the device on the pad of the charger. This limits the usefulness of the wireless charging station for transmitting power. Although labs have been experimenting with larger setups that can charge devices placed anywhere within a room, reports of beaming electricity outdoors and for long distances have been rather scarce.

PowerLight has been experimenting with wireless power transfer for quite some time now, and they have partnered with Ericsson, a telecommunications company, for a proof of concept demonstration. Their system consists of two components, a laser transmitter, and a receiver. The distance between the transmitter and receiver can vary from a few hundred meters to a few thousand meters.

However, unlike a Tesla coil, the PowerLight device does not transmit electricity directly. Instead, at the transmitter end, electricity powers a powerful laser beam, sending it directly to the receiver. In turn, the receiver uses specialized photocell arrays to convert the incoming laser back into electricity for powering connected devices.

Such a powerful laser-blasting through the open air can be a dangerous thing. Therefore, PowerLight has added many safeguards. They surround the beam with wide cylinders of sensors that can detect anything approaching. The sensors can shut off the beam within a millisecond, if necessary. In fact, the safety system is so fast that a flock of birds is not affected when flying through the laser beam, but there is an interruption at the receiver.  To overcome such fleeting interruptions, and cover longer-term disruptions as well, the PowerLight system has a battery back-up at the receiver end.

PowerLight is using their system to power a 5G radio base station from Ericsson, that has no other power source connected to it. The base station received 480 watts from the transmitter placed at a distance of 300 m. However, according to the PowerLight team, the technology can send 1000 watts over a distance of over 1 km. They also claim there is room for future expansions.

Wirelessly powering these 5G units could make them more versatile, as they will then become portable, and capable of operating in temporary locations. This will also allow them to operate in disaster areas, where there has been a disruption of infrastructure.

According to PowerLight, their optical power beaming technology may be useful in several other applications also, such as for charging electric vehicles, in future space missions, and in adjusting the power grid operations on the fly.

Where Do You Use Encoders?

All kinds of mechanical systems use a critical component commonly known as an encoder. Large industrial machines performing delicate work, high-precision prototyping, or repeatable tasks use encoders predominantly. Production of advanced electronics also requires the use of encoders. Encoders can be linear, angle, or rotary and the electronics sector uses them in some form or the other. Semiconductor fabrication, with its small components and work areas, requires encoders of the highest resolution and accuracy.

Production of electronics often uses vacuum environments with unique ventilation. These environments require special types of encoders, including linear and angle types made specifically to operate with the temperature and gaseous conditions prevalent with vacuum environments.

CNC machines must maintain their accuracy and position even when operating with heavy spindles and workpieces, high speeds, and multi-axis movements. All the components need to work together for accurate milling, drilling, and boring. Encoders play an important role in the synchronous working of CNC machines. For instance, custom linear encoders guide the travel of the axes of a milling machine.

At present, the automation industry is striding ahead rapidly and requires capable encoders. Strausak, a grinding machine company, makes robotic arms that manufacturing environments use universally. Unmanned mechanical systems must rely on accurate and consistent measurement and motion provided by encoders.

Automated transportation, such as high-speed trains in Sweden, depends on custom-made absolute encoders. These encoders operate a redundant system for automatically controlling the speed and braking of the train when necessary.

The medical industry requires precision and accuracy along with safety for testing and treating the human body while developing new procedures in the lab. CT and MRI scanning machinery use exposed linear and rotary encoders for precision imaging and maintaining patient safety. Precision angular and linear encoder technology help radiation therapy, leaving no room for error.

For instance, GammaPod, the most advanced breast cancer treatment in the world, depends on absolute rotary encoders for operating its stereotactic radiotherapy system. The medical industry depends on encoders predominantly because of the precision necessary for safely and accurately testing and treating the human body.

Robotics often uses articulating arms for picking and placing objects and equipment in manufacturing plants. They also use mobile, guided, and automated robots, which, in turn, require encoders for their proper functioning. For instance, encoders provide automated systems with the necessary and effective position and speed feedback for allowing them to function with minimum human intervention. Robotics often uses low-profile encoders that can fit inside small robotic arms.

All types of encoders are available for serving the general purpose of measuring motion and providing signaling feedback. However, their capabilities, configurations, and applications vary significantly and widely. In every facet of life, encoders play a significant role. This is especially applicable in the industrial and technological world, where safety, accuracy, and precision are important parameters to uphold.

Knowledge of the encoder transfer function is important for selecting the proper resolution for incremental optical encoders and for tuning the regulator depending on the speed and torque of the application. The implementation of a proper control loop impacts the stability and performance of the application.

Battery Electrolyte from Wood

Although there exist several types of batteries, all of them function with a common concept—batteries are devices that store electrical energy as chemical energy and convert this chemical energy into electricity when necessary. Although it is not possible to capture and store electricity, it is possible to store electrical energy in the form of chemicals within a battery.

All batteries have three main components—two electrodes or terminals made of different metals, known as anode and cathode, and the electrolyte separating these terminals. The electrolyte is the chemical medium allowing the flow of electrical charges between the terminals inside the battery, When a load connects to a battery, such as an electrical circuit or a light bulb, a chemical reaction near the electrodes creates a flow of electrical energy through the load.

The most commonly used battery today, the lithium battery, typically uses a liquid electrolyte for carrying electrical charges or ions between its electrodes. Scientists are also looking at alternatives like solid electrolytes for future opportunities. A new study offers cellulose derived from wood as one type of solid electrolyte. The advantage of this solid electrolyte from wood is its paper-thin width, allowing the battery to bend and flex for absorbing stress while cycling.

The electrolyte presently in use today in lithium cells has the disadvantage of containing volatile liquids. There is thus a risk of fire in case the device short-circuits. Moreover, there is the possibility of the formation of dendrites—tentacle-like growths—and this can severely compromise the battery’s performance. On the other hand, solid electrolytes, made from non-flammable materials, allow the battery to be less prone to dendrite formation, thereby opening up totally modern possibilities with different battery architecture.

For instance, one of these possibilities involves the anode, one of the two electrodes in the battery. Today’s batteries usually have an anode made from a mix of copper and graphite. With solid electrolytes, scientists claim they can make the battery work with an anode made from pure lithium. They claim the use of pure lithium anode can help to break the bottleneck of energy density. Increased energy density will allow planes and electric cars to travel greater distances before recharging.

Most solid electrolytes that scientists have developed so far are from ceramic materials. Although these solid electrolytes are very good at conducting ions, they cannot withstand the stress of repeated charging and discharging, as they are brittle. Scientists from the University of Maryland and Brown University were seeking an alternative to these solid electrolytes, and they started with cellulose nanofibrils found in wood.

They combined the polymer tubes they derived from wood with copper. This formed a solid ion conductor with conductivity very similar to that in ceramics, and much better than that from any other polymer ion conductor. The scientists claim this happens as the presence of copper creates space within the cellulose polymer chains allows the formation of ion superhighways, enabling lithium ions to travel with substantially high efficiency.

With the material being paper-thin and thereby highly flexible, scientists claim it will be able to tolerate the stresses of battery cycling without damage.

Improving Computer Vision with Two AI Processors

Computer vision is becoming a necessity in IoT and automotive applications. Engineers are trying for the next level in computer vision with two AI processors. They hope that two AI processors will help to make computer vision not only more efficient but also more functional.

One of the fastest-growing applications of artificial intelligence, computer vision is jostling for attention between prestigious fields like robotics and autonomous vehicles. In comparison to other artificial intelligence applications, computer vision has to rely more on the underlying hardware, where the underlying imaging systems and processing units overshadow the software performance.

Therefore, engineers are focusing on cutting-edge technology and state-of-the-art developments for the best vision hardware. Two companies, Intuitive and Syntiant, are now making headlines by supporting this move.

Israeli company, Intuitive, recently announced that its NU4000 edge Artificial Intelligence processor will be used by Fukushin Electronics in their new electric cart, POLCAR. The processor will allow the cart to have an integrated obstacle detection unit.

Requiring top performance and power efficiency when operating a sophisticated object detection unit in a battery-powered vehicle like an electric cart made Fukushin use the NU4000. The edge AI processor from Intuitive is a multicore System on a Chip or SoC that can support several on-chip applications. These include computer vision, simultaneous localization and mapping or SLAM, and 3d depth-sensing.

The NU4000 achieves these feats by integrating three Vector Cores that together provide 500 COPS. There is also a dedicated CNN processor offering three CPUs, 2 TOPS, a dedicated SLAM engine, and a dedicated depth processing engine. Intuitive has built this chip with a 12nm process, and it can connect up to two displays and six cameras with an LPDDR4 interface.

With a small form factor and low power consumption, the NU4000 is a powerful processor providing several key features that could make the obstacle detection unit a special application for Fukushin’s POLCAR.

California-based Syntiant was in the news with their Neural Decision Processor, the new NDP200. Syntiant has designed this processor for applications using ultra-low-power, especially useful for deep learning. With a copyrighted Syntiant core as its core architecture, it has an embedded processor, the ARM Cortex-M0. With this combination, the NDP200 achieves operating speeds up to 100 MHz.

Meant for running deep neural networks like RNNs and CNNs, Syntiant has optimized the NDP200, especially for power efficiency. Deep neural networks are necessary for computer vision applications.

Syntiant claims NDP200 performs vision processing at high inference accuracies. It does this while keeping the power consumption below 1 mW. Judging its performance, the chip could reach an inference acceleration of more than 6.4 GOP per second, while supporting more than 7 million parameters. This makes the NDP200 suitable for edge computing of larger networks.

Syntiant expects its chip will be suitable for battery-powered vision applications, such as security cameras and doorbells. In fact, the combination of the chip’s capability to run deep neural networks and power efficiency can allow it to take the next evolutionary step towards creating a better processor for computer vision applications.

Low-Power Circuit Timing using SPXOs

A wide range of electronic devices relies on circuit timing as a critical function. These include microcontrollers, Bluetooth, Ethernet, Wi-Fi, USB, and other interfaces. In addition, circuit timing is essential for consumer electronics, wearables, the Internet of Things (IoT), industrial control and automation, test and measuring equipment, medical devices, computing devices and peripherals, and more. Although designing crystal-controlled oscillators seems an easy process for providing system timing, there are numerous design requirements and parameters that designers must consider when matching a quartz crystal to an oscillator chip.

Among the several considerations are the negative resistance of the oscillator, its drive level, resonant mode, and the motional impedance of the crystal. When the designer is making the circuit layout, they must consider the parasitic capacitance of the PC board. They must also consider the on-chip integrated capacitance, and include a guard band around the crystal. Finally, the design must not only be compact, with a minimum number of components, and reliable. While the circuit must be capable of operating with a wide range of input voltages, consuming minimal power, it must also have a small root-mean-square jitter.

An optimal solution to the above is to use simply packaged crystal oscillators or SPXOs. Manufacturers optimize SPXOs for low RMS jitter and minimal power consumption. These devices can operate with any supply voltage ranging from 1.6 VDC to 3.6 VDC. With these continuous-voltage oscillators, designers can implement solutions requiring minimal effort while integrating them into digital systems.

In small, battery-powered, wireless devices, power consumption is always a very important consideration. That is why designers prefer to base such devices on the system on a chip or SoC processor that consumes very low power to support battery lives of several years. Moreover, device cost depends on the battery size, as the battery is easily the most expensive component in the device—minimizing the battery size is, therefore, an important factor in small wireless devices. For battery life consideration, one of the important parameters is the standby current, apart from the self-discharge current of the battery. Minimizing the current drawn by the clock oscillator is important, as this is greater than the standby current.

Designing low-power oscillators can be challenging. Designers are tempted to save energy by allowing the circuit to enter a disabled state for minimizing the standby current while starting the oscillator when needed. However, this is not an easy task as starting crystal oscillators quickly is not a simple and reliable task. Reliable start-up conditions require careful design efforts when designers attempt it across all environmental and operating conditions.

Most low-power wireless SoCs favor the Pierce oscillator configuration. The circuit has crystal and tow load capacitors. It uses an inverting amplifier that has an internal feedback resistor. With the amplifier feeding back its output to its input, the right conditions cause a negative resistance to start the oscillations going.

Quartz crystal oscillators can have jitters caused by power supply noise, improper load, improper termination conditions, the presence of integer harmonics of the signal frequency, circuit configurations, and amplifier noise. The designer must use several methods to minimize jitter.

Cooling Modes in Electronic Loads

Applications based on renewable energy are thriving. This is leading to a requirement for increased testing of devices that generate renewable DC power—devices like solar panels, fuel cells, and batteries, to name a few. This testing is typically by employing electronic loads, mostly programmable and with a design that can draw various specified amounts of power from the source. In the lab or on the production floor an electronic load is the most suitable instrument to characterize devices producing DC output.

Selection of an electronic load requires careful consideration of several options like the voltage, current, and power ratings; operating modes; cooling methods; transient response times; calibration techniques; computer interfaces; and protective features.

Starting with the choices for voltage, current, and power ratings, most users also look for subtleties like the need for a load capable of sinking high currents at very low voltages. The cooling method is typically based on power rating, either a water-cooled device or an air-cooled one. Air-cooled loads have the advantage of flexibility—they can be self-contained, capable of being moved anywhere in the facility without the need for plumbing. On the other hand, water-cooled loads are smaller and less expensive as compared to air-cooled loads of the same power rating. Moreover, water-cooled loads will not load the HVAC system with extra heat generation. Usually, the HVAC system may not consider a 1 kW air-cooled load as a burden, but a 50 kW air-cooled load will certainly tax the HVAC system.

A number of factors determine the exact power level above which a user might consider a water-cooled load as preferable. Apart from the application, this might include the space and facility available. Most programmable electronic loads employ field-effect transistors or FETs. According to a rule of thumb, the air-cooled design uses only 50% of the capacity of each FET, and a water-cooled design uses up to about 85%. This results in a 35% saving in the number of FETs at a given power level for a water-cooled load. Not only does this lead to a reduction is costs, but also space requirements. For instance, at a 7.5 kW rating, an air-cooled load can cost roughly twice as much for a water-cooled load.

On the other hand, water-cooled loads lack the flexibility that is inherent in an air-cooled unit. Moreover, to use a water-cooled load, the user must install a water-cooling infrastructure, such as a chiller and associated plumbing. Depending on the layout of the user’s facility, this might be a costly and difficult task. Moreover, a chiller may need an expansion in the future, and the plan must accommodate it.

Operating modes need consideration next. Broadly, electronic loads operate in two modes—constant current and constant voltage. The constant current mode allows the load to sink a specific current, irrespective of the input voltage, provided the load’s specifications are not exceeded. In the constant voltage mode, the load will sink variable amounts of current to maintain a constant voltage at its input. Some loads will also offer additional modes like constant-power and constant-resistance modes.