Enhancing industrial energy efficiency with SiC and GaN technology

Improving industrial energy efficiency

As the world moves away from fossil fuels and towards an increasing use of electricity, energy efficiency for industry is of growing importance. Some 45% of the entire world’s energy use is accounted for by industry, with two thirds of this being used by motors. This makes energy efficient motors a major priority for much of industry.

Although the increased electricity demand will in large part be met by renewable sources, much will still be generated by fuels such as natural gas, which contribute to the carbon dioxide being released to the atmosphere. Renewable sources are also intermittent and require load balancing technologies to be truly viable.

With primary sources such as gas under extreme price pressure, industry needs to improve its use of electricity, adopting technologies that ensure it does the maximum amount of useful work and is not wasted.

This need is enhanced by a growing shift to automation to achieve the goals of high quality repeatable production, production flexibility and consumer demand for more bespoke, personalized products. Robots, automated cells, autonomous guided vehicles and associated handling equipment such as cranes, conveyors and warehousing solutions all help meet these needs but pose an additional load on the plant’s power supply.

Industry is also increasingly adopting Industry 4.0 techniques, integrating sensors, local processing, connectivity networks, software and the Cloud to analyse production data and machine performance to optimise quality, production time and maintenance efforts. Much of the subsequent processing is performed in remote, energy hungry data centres, representing another load on the electricity supply.

As power demand grows, all these plant facilities and remote data processing sites will need power supplies that are highly efficient.

For these reasons, there is great pressure from industry, government, and manufacturers alike to develop more efficient power supplies. Among the biggest challenges for designers of power supplies, three characteristics stand out – power density, thermal performance, and conversion efficiency. Although traditional improvement methods will continue to have some value, significant advances in energy performance will demand a radically new approach.

New semiconductor technology

Recent efforts to improve the energy efficiency of power devices such as chargers and amplifiers has focused on improving the performance of the semiconductors they are based on.

In particular, work is taking place in the field of wide band gap semiconductors, which can offer substantial performance improvements over silicon based components. The bandgap is an energy range in a solid where no electrons can exist and is one of the factors determining how well a solid material can conduct electricity – the wider the bandgap, the higher the voltage and temperature it can sustain.

The two major technologies in this area are SiC (Silicon Carbide) and GaN (Gallium Nitride).

SiC is a compound semiconductor composed of silicon and carbide. With a bandgap that is three times greater than silicon at 3.4 eV, it provides several advantages, including ten times the breakdown electric field strength. SiC power semiconductors can be used for much higher power device voltages than traditional silicon, ranging from 600V to thousands of volts. The technology is typically used in high power applications of 10 kV and beyond, and offers lower switching losses and lower cost, but with lower reliability.

Gallium Nitride (GaN) is a very hard and mechanically stable semiconductor. With a wide bandgap of around 3.2 eV, a GaNFET will offer a much higher breakdown strength, faster switching speed, higher thermal conductivity and lower resistance than silicon based equivalents with bandgaps of around 1.12eV.

It is also more robust, reliable, and radiation hardened.

Figure 1: Key material properties of Wide-Bandgap Semiconductors

Although SiC and GaN serve different voltage, power and application needs, they also overlap in some equipment applications. Offering voltage levels as high as 1,200 V with high current-carrying capabilities, SiC devices can benefit applications such as automotive and locomotive traction inverters, large three phase grid converters and high-power solar farms and. By contrast, GaN provides superior switching, inherent manufacturing and cost advantages and the ability to switch at much higher frequencies. This has made it the natural choice for many designers looking to develop applications of less than 10kW.

Industrial applications that benefit from SiC and GaN

Power supplies

The characteristics of SiC-based components make power supplies one of the major SiC applications, allowing power supply designers to achieve new heights in efficiency. SiC power electronics can have an impact in a number of industrial applications, perhaps most notably in Power Factor Correction (PFC). This is the technique of compensating for the lagging current by creating a leading current through connecting enough capacitance in the circuit to adjust the power factor to as close to zero as possible.

Increasing the power factor of a power supply can drastically reduce wasted power. PFC effectively shapes the input current to maximize the power realized from the supply. The higher frequency enabled by SiC allows smaller and more affordable circuit components to be the used in the power supply.

Using SiC MOSFETs requires fewer components, is more cost effective, and gives a higher power density, cutting system size, weight, and thus costs.

According to Wolfspeed, SiC can deliver up to 25% fewer losses, up to 60% smaller systems and up to 20% lower costs when compared to silicon semiconductors.

The higher efficiency also improves thermal performance, further reducing the size and weight of the power supply.

Motors and drives

Currently, 45% of the world’s electricity is taken up by industry, with two thirds of that use accounted for by motors in a huge range of applications including bulk conveying, packaging machines and the numerous uses of pumps and fans. Yet, some 30% of that energy is wasted. Clearly, increased energy saving for motors and drives is required and GaN semiconductors can provide this.

Benefits of high GaN efficiency for motor and drive applications include a 98% energy conversion efficiency, compared to 92% for regular silicon. Regeneration and active infeed can provide an approximately 22% lower power consumption, while overall, there is a 25% lower electricity usage with GaN.

Other benefits include:

• A 50% smaller size
• A 15% lower cost of the motor drive
• Cost savings from the use of unshielded cables and no requirement for external filters
• No acoustic noise
• Longer motor lifetimes

Examples include products by Siemens, which has released a GaN-based drive as part of its Simatic Micro-Drive product line. Offering increased efficiency and faster motor response time, these mini drives are only two centimetres wide and require no additional cooling due to the use of GaN.

Robots

GaN semiconductors offer particular benefits in robotic applications, particularly when needing to optimize the size and make robots easier to integrate in factory environments. For example, high frequency leads to smaller magnetics, capacitors and filters, while GaN’s lower power losses allow the use of smaller motors on the robot that do not require heat sinks. In turn, this small size leads to easier integration.

These devices also allow wireless charging, which offers true autonomy to mobile robots - freeing them from cables, it allows them to operate in all axes, with complete 360-degree freedom. GaN transistor technology can cope with the high energy levels needed for wireless charging, which for robot applications, demands the use of a large charging area and charging at a distance much greater than existing wireless systems used for products such as smartphones.

Wireless charging for robots would be at a frequency of 500 kHz up to one MHz. Silicon, on the other hand, is limited to frequencies from 100-200 kHz. Using GaN based electronics operating at these high frequencies, robots can charge at multiple locations several times a day, without the need to physically dock with a charging connector.

Automotive

Automotive applications offer great scope for using power efficient GaN and SiC semiconductors. One of the biggest beneficiaries is automotive electrical systems. Modern Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) contain equipment that can use these devices, including DC/DC converters, on board chargers (OBCs), motor drivers, and LiDAR.

Both GaN and SiC semiconductor are proving their worth in areas such as battery management in electric vehicles. As well as handling much higher voltages than silicon, their high speed switching also makes them particularly suitable for battery management, while the ability to block high voltages is seeing them increasingly used in voltage regulators for EVs.

Conclusion

As the world transitions to a reliance on electrical energy systems and away from fossil fuel based sources, it is more important than ever to make better use of the available energy by making products and systems as efficient as possible.

Particularly important are power control solutions such as converters, amplifiers and chargers widely used in industrial applications that use motors or rely on battery power to achieve greater autonomy. The efficiency of these devices largely comes down to the power semiconductors used and there are now choices that go beyond the capabilities of basic silicon.

SiC is now commonly used in power applications with 650V to 1700V ratings matching common single- and three-phase industrial and inverter levels. SiC devices have proven their value as rugged, state-of-the-art drivers in a growing number of applications, while GaN devices are finding increasing use in lower voltage applications where the material provides the best balance of efficiency and performance.

With greater use of these technologies in a wide range of industrial applications, energy use can be made much more efficient, benefitting not only the costs of energy using companies but also the society at large.