Explore the future of transportation with our e-magazine, covering how wide bandgap semiconductors are reshaping mobility. Learn about residual current monitors for EV charging safety, AEC-Q200 qualified fuses for automotive reliability, and advanced solutions like integrated FOC motor control and sensors to reduce EV range anxiety. Stay updated on the latest semiconductor innovations driving safer, more efficient transportation.
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Transportation | Volume 9
Wide bandgap semiconductors are reshaping the
transportation world How to use residual current monitors to ensure electrical safety when charging electric vehicles AEC-Q200 qualified fuses play a critical role in the automotive environment Reduce EV range anxiety and improve safety using integrated FOC motor control and advanced sensors
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Editor’s note In today’s rapidly changing world of transportation, exciting new technologies are transforming how we move. Wide bandgap semiconductors are making electricvehicles more efficient and powerful, while LiDAR technology is bringing us closer to the reality of self-driving cars by improving navigation and safety. As morepeople turn to electric vehicles, sensors play an essential role in keeping the charging process safe and reliable. Automotive security is also getting a boost fromAEC-Q200 standards, ensuring that vehicles can handle even the toughest conditions. Tackling electric vehicle range anxiety is another key step in making thesecars safer and more appealing, and CAN bus systems help keep everything running smoothly behind the scenes. Together, these innovations are shaping a smarter,safer future for everyone on the road.
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Wide bandgap semiconductors are reshaping the transportation world
Quick guide to GaN FETs for LiDAR in autonomous vehicles
Special feature: retroelectro Frank J Sprague and the Richmond Union Passenger Railway
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How to use residual current monitors to ensure electrical safety when charging electric vehicles
The selection and use of FPGAs for automotive interfacing, security, and compute-intensive loads
AEC-Q200 qualified fuses play a critical role in the automotive environment
Reduce EV range anxiety and improve safety using integrated FOC motor control and advanced sensors
The basics of the controller area network (CAN bus) and its use in automotive applications
You want to put how much current through your PCB?
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Wide bandgap semiconductors are reshaping the transportation world
Property
SI
SIC
GAN
Bandgap energy (eV)
1.1
3.2
3.4
Breakdown electric field (MV/cm²)
0.3
3.5
3.3
Electron mobility (cm²/V•s)
1500
900
900-2000
Electron saturation velocity (cm/s)
1 • 107
2.2 • 107 2.5 • 107
Thermal conductivity (W/cm•K)
1.5
5.0
1.3
Dielectric constant
11.8
10
8.9
Table 1: Comparison of the properties of Si, SiC, and GaN.
Table 1 lists the main properties of silicon carbide (SiC) and gallium nitride (GaN), the two most popular WBG materials, compared to silicon. The main advantages of SiC power devices, compared to silicon-based counterparts, are the following: ■ Low switching losses: SiC MOSFETs are unipolar devices that exhibit very low turn- on and turn-off switching losses. This property enables higher switching frequencies with lower losses, allowing the reduction of passive components and magnetics ■ Low conduction losses: due to the absence of a bipolar junction, SiC devices can also reduce losses during light-load or partial-load operation
■ High operating temperatures: silicon carbide offers superior thermal properties compared to silicon. SiC exhibits low leakage currents over a wide range of temperatures, allowing operation beyond 200°C. Simplified cooling and excellent thermal management are a consequence of this property ■ Intrinsic body diode: thanks to this characteristic, SiC MOSFETs can operate in diode mode in the third quadrant providing excellent performance in power applications Combining the above properties allows obtaining SiC devices with higher power density, efficiency, operational frequencies, and smaller footprint.
Properties of WBG materials
Wide bandgap materials are quickly transforming the power electronics area due to their advantages over commonly used silicon (Si). While silicon has a bandgap of 1.1 electronvolts (eV), WBG materials have a bandgap of 2 to 4 eV. Additionally, the breakdown electric field of most WBG semiconductors is substantially higher than silicon. That means they can operate at significantly higher temperatures and voltages, providing higher power levels and lower losses.
The entire transportation sector is undergoing a radical transformation, with internal combustion engine (ICE) vehicles gradually giving way to less polluting electric and hybrid cars and cleaner mass transportation solutions (trains, aircraft, and ships). Solutions capable of maximizing efficiency and reducing environmental impact are needed to contain greenhouse gases (GHG) emissions and mitigate global warming. Wide bandgap (WBG) semiconductors exhibit several properties that make them attractive for transportation applications. Their usage can result in more efficient, faster, and lightweight vehicles with improved range and reduced environmental impact.
By Rolf Horn Contributed By DigiKey's North American Editors
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Wide bandgap semiconductors are reshaping the transportation world
The main advantages of GaN power devices , compared to Si and SiC counterparts, are the following: ■ GaN devices can operate in the third quadrant without reverse recovery charge even though they do not have an intrinsic body diode. As a result, there is no need for an anti-parallel diode ■ Low gate charge QG and on- resistance RDS(ON), which translate into lower drive losses and faster switching rates ■ Zero reverse recovery, resulting in lower switching losses and less EMI noise ■ High dv/dt: GaN can switch at very high frequencies and has 4x faster turn-on and 2x faster turn-off than SiC MOSFETs with similar RDS(ON)
Figure 2: Main components of a H/EV. (Source: ROHM Semiconductor)
Figure 1: Potential applications of Si, SiC, and GaN devices. (Source: Infineon )
Rail transportation Electric trains draw power from the grid via a catenary line or a third rail, converting it into a form suitable for the motors and the auxiliary systems. If the train operates on an AC line, a transformer and rectifier must step down and condition the voltage to DC. The DC voltage is then split and delivered through inverters to address the needs of the auxiliary and traction systems. The traction inverter transforms DC into AC for powering the motors and reconditions the electricity produced by regenerative braking. Therefore, this converter is designed to run a bidirectional flow of energy. Instead, the auxiliary
Onboard Charger
Inverter and HV Converter
Type
LV Converter
Hybrid and electric vehicles
on the topology of the inverter. SiC helps reduce losses, size, and weight, allowing solutions with small form factors. The onboard charger (OBC) connects to the grid, converting AC into DC voltage to charge the battery. OBC output power is usually between 3.3 kW and 22 kW and relies on high voltage (600 V and above) power devices. While both SiC and GaN are suitable for this application, GaN’s features, like high switching frequency, low conduction losses, and reduced weight and size, make it the ideal solution for implementing OBCs.
Power
3.3 kV >
12 kW to 400 kW 1 kW to 10 kW
H/EVs use several power electronics systems to transform grid or engine energy into a form suitable for powering motor and auxiliary devices. Most H/EVs also use regenerative braking, in which the wheels rotate the generator to charge the battery. The traction inverter is a crucial component in these vehicles, converting the DC high voltage from the batteries into AC for powering the three-phase motor (see Figure 2). Due to the high power involved, SiC devices are preferred in this application, with a rating of 650 V or 1.2 kV, depending
Input V
120 V to 240 V 200 V to 400 V 200 V to 400 V
Output V
200 V to 400 V 100 V to 650 V 12 V to 48 V
Si efficiency
85% to 93% 83% to 95%
85% to 90%
Applications of WBG devices
SiC efficiency
95% to 96%
96% to 97%
96% to 99%
GaN efficiency
94% to 98%
Not Available
95% to 99%
As highlighted in Figure 1, there are applications where SiC and GaN offer the best performance and others where their characteristics overlap those of silicon. Often, GaN devices are the best choice for high-frequency applications, whereas SiC devices have high potential at high voltages.
Discrete 600 V to 900 V
Discrete/Module 600 V to 1200 V
Discrete 600 V to 900 V
Power device
Table 2: Applications of WBG in H/EVs and comparison of performance with Si.
Another application of WBG in H/ EVs is the low-voltage (LV) DC-DC converter, responsible for stepping down the battery voltage (200 V in HEVs, above 400 V in EVs) to the 12 V/48 V DC voltage required for
powering the auxiliary systems. Featuring a typical power of less than 1 kW, the LV converter can achieve higher frequencies using GaN and SiC devices.
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Wide bandgap semiconductors are reshaping the transportation world
(a mixture of AC-DC and DC-AC converters) and other loads are primarily among them. Recent trends in the marine sector are trying to replace AC electrical distribution networks with DC distribution networks. This solution removes the need to synchronize the generators to the AC power distribution, provided they can operate at variable speeds, and achieves fuel savings. On the other hand, it requires the introduction of rectifier circuits (AC-DC converters) between AC generators and the DC power distribution network. Marine propulsion variable speed drives are crucial ship components that must operate with extreme reliability. They are frequently rated from a few watts to a few tens of megawatts. Often, these drives are the most significant power conversion blocks in a ship with AC electrical power distribution. Hence their great efficiency is crucial. Once more, conventional silicon- based power devices are being replaced by SiC and GaN devices, which increase efficiency while reducing size and weight. WBG devices will soon overtake Si- based devices as the industry leader, bringing cutting-edge power electronics system solutions that are impossible with silicon technology. Future fuel-turbine-powered electrical generators will be the prime mover for hybrid and all-
electric avionic propulsion systems. Power electronics will subsequently be used to connect the generator and motor. Very high DC voltage buses are necessary to ensure enough power can be available. These buses can range in voltage from a few kVs for light vehicles to the MV range for airplanes. Moreover, a high DC voltage bus makes it possible to use permanent magnet synchronous machines as generators, which lowers reactive power and the power electronics' rating. The power converters need equipment that can function at high switching frequencies due to the fast generator rotational speed, which results in smaller and lighter filter elements.
temperatures with lower power loss. These characteristics make them particularly well-suited for power electronics used in various applications, including transportation. WBG semiconductors are used in the transportation industry to develop more efficient and reliable electric and hybrid vehicles. The lower power loss of wide bandgap semiconductors allows higher switching frequencies, reducing power electronics' size and weight. This, in turn, can result in greater vehicle range, faster charging times, and improved overall performance. Wide bandgap semiconductors also enable the development of more compact and efficient powertrains, including motor drives and inverters for EVs and HEVs. By reducing the size and weight of these components, vehicle designers can free up space for other components or improve the vehicle’s overall aerodynamics. In addition to electric and hybrid electric vehicles, wide bandgap semiconductors are also used in other transportation forms, such as airplanes and trains. In these applications, the high temperature and high voltage capabilities of wide bandgap semiconductors can improve the efficiency and reliability of power electronics, leading to reduced operating costs and improved safety.
Power losses in the electric rail can be drastically reduced with WBG power electronics. As a result, less energy will be drawn from the grid, and more will be returned via regenerative braking. WBG devices also offer additional benefits that considerably help rail transportation in addition to efficiency increases, such as: ■ Reduced weight has significant impacts on efficiency ■ Higher operating temperature allows for a smaller cooling system ■ Increased switching frequency enables smaller passive dimensions, which lowers the weight of the traction and auxiliary inverters. The inverter and motor can respond to variations in demand more quickly thanks to the higher switching frequency, thus boosting efficiency. Finally, since the higher frequency is less audible and cooling fans may be turned off, railway stops would be less noisy when trains are present.
inverter supplies power for cooling systems, passenger comfort, and other non-movement-related needs. The size of the power electronics within the traction inverter depends on the class of train: ■ Transit trains: 1.2 kV to 2.5 kV ■ Commuter trains: 1.7 kV to 3.3 kV ■ Intercity trains: above 3.3 kV However, most trains use either 3.3 kV or 1.7 kV. Regenerative braking, which returns a part of the electricity to the local grid, rail power distribution system, or energy storage, makes the system more complicated than those in the previously stated applications. Regenerated energy must be stored or used immediately; otherwise, it is lost.
Bipolar Si-based IGBTs and freewheeling diodes, traditionally used in power modules for railway traction applications, can be replaced by unipolar SiC-based MOSFETs and diodes, thus increasing the switching frequency and power density. Conduction and switching losses must be decreased, and the maximum junction temperature must be raised to reduce the weight and volume of the power electronic equipment used in
Silicon carbide is the most promising semiconductor
device to meet all requirements while ensuring high conversion efficiency. For aircraft in the lower power range, newly created 3.3 kV and 6.5 kV SiC MOSFET devices are of significant interest. They can also be employed in modular power converter topologies to meet larger aircraft's higher voltage/power requirements.
railway traction applications. For the widely used bipolar
silicon power devices, increasing conduction losses and decreasing switching losses have the opposite effects. A unipolar device does not experience the trade-off between the conduction and switching losses as bipolar devices do. As a result, switching losses could be reduced while minimizing conduction losses.
Marine and aviation applications
Conclusion
Power electronics innovations have benefited the marine sector for a long time. On the ship, medium voltage AC level electricity from synchronous generators powered by diesel engines is supplied to various loads. Propulsion drives
Wide bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), offer several advantages over traditional semiconductors in their ability to handle high voltages and
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Quick guide to GaN FETs for LiDAR in autonomous vehicles
Designing a high-power and high-performance gate driver that meets the safety requirements of IEC 60825-1 using discrete components is complex and time consuming, potentially adding to cost and extending time to market. To meet these challenges, designers can turn to integrated, high-speed gate driver ICs paired with gallium nitride (GaN) power field effect transistors (FETs). Using an integrated solution minimizes the parasitics that degrade the integrity of the drive signal, particularly in the high- current laser power loop, and it enables locating the high-current driver close to the power switches, minimizing the effect of high- frequency switching noise.
This article provides a brief introduction to LiDAR. It discusses applications and safety requirements before reviewing the challenges of designing automotive LiDAR, focusing on the high-current laser power loop. It then presents LiDAR solutions from Efficient Power Conversion (EPC), Excelitas Technologies , ams OSRAM , and Texas Instruments, including GaN power FETs, gate drivers, and laser diodes, along with evaluation boards and implementation guidance to speed the development process.
How LiDAR works
LiDAR systems measure the round- trip time-of-flight (ToF) (Δt) of a laser beam pulse to calculate the distance from an object (Figure 1). The distance (d) can be calculated using the formula d = c * Δt/2, where c is the speed of light in air. Short pulse durations are one of the keys to LiDAR. Given that the speed of light is approximately 30 centimeters per ns (cm/ns), a 1 ns LiDAR pulse has a length of about 30 cm. This puts a lower limit of about 15 cm on the minimum feature size that can be resolved. As a result, LiDAR pulses must be limited to a few nanoseconds to have a useful resolution for human- scale environments.
Light detection and ranging (LiDAR) applications include autonomous vehicles, drones, warehouse automation, and precision agriculture. Humans are present in most of these applications, leading to concerns about a LiDAR laser’s potential to cause eye damage. To prevent injury, automotive LiDAR systems must meet IEC 60825-1 Class 1 safety requirements while transmitting at up to 200 watts. The general solution uses a pulse of 1 to 2 nanoseconds (ns) at a 1 to 2 megahertz (MHz) repetition rate. This is challenging as a microcontroller or other large digital integrated circuit (IC) is needed to control the laser diode but cannot directly drive it, so a gate driver circuit must be added. Also, this gate driver design must be optimized to ensure that the performance of the LiDAR system is suitable for Society of Automotive Engineers (SAE) Level 3 and higher advanced driver assistance (ADAS) systems.
By Kenton Williston Contributed By DigiKey's North American Editors
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Quick guide to GaN FETs for LiDAR in autonomous vehicles
Pulse width, peak power, repetition frequency, and duty cycle are primary LiDAR specifications. For example, a typical laser diode used in a LiDAR system may have a pulse width of 100 ns or less, a peak power of >100 watts, a 1 kilohertz (kHz) or higher repetition frequency, and a duty cycle of 0.2%. The higher the peak power, the longer the detection range of the LiDAR, but thermal dissipation is a tradeoff. For a pulse width of 100 ns, the average duty cycle is usually limited to 0.1% to 0.2% to prevent laser overheating. Shorter pulse widths also contribute to LiDAR safety. IEC 60825-1 defines laser safety in terms of the maximum permissible exposure (MPE), which is the highest energy density or power of a light source with negligible potential to cause eye damage. To be negligible, the MPE power level is limited to roughly 10% of the energy density, which has a 50% possibility of causing eye damage. With a constant power level, shorter pulse widths have a lower average energy density and are safer. While a single LiDAR ToF measurement can determine the distance to an object, thousands or millions of LiDAR ToF measurements can be used to create a three-dimensional (3-D) point cloud (Figure 2).
A point cloud is a collection of data points storing large amounts of information called components. Each component contains a value describing an attribute. The components may include x, y, and z coordinates and information about the intensity, color, and time (to measure object movement). LiDAR point clouds create a real-time 3-D model of the target area.
Designers can use EPC’s EPC9179 development board for a fast start by employing the EPC2252 in LiDAR systems with total pulse widths of 2 to 3 ns (Figure 4). The EPC9179 includes an LMG1020 gate driver from Texas Instruments that can be controlled by an external signal or an onboard narrow-pulse generator (with sub- nanosecond precision).
The IC is delivered as a die-size ball grid array (DSBGA). This means the passivated die is directly attached to solder balls without any other packaging. As a result, the DSBGA chips are the same size as the silicon die, minimizing their form factor. In this case, the EPC2252 uses a 9-DSBGA implementation that measures 1.5 x 1.5 millimeters (mm). It has a thermal resistance of 8.3°C per watt (˚C/W) from junction to board, making it suitable for high-density systems.
Use GaN FETs to power LiDAR lasers
Figure 1: LiDAR uses ToF measurements to detect objects and determine their distance. (Image source: ams OSRAM)
GaN FETs switch much faster than their silicon counterparts, making them suitable for LiDAR applications requiring very narrow pulse widths. For example, the EPC2252 from EPC is an AEC-Q101 automotive- qualified 80 volt GaN FET capable of current pulses up to 75 amperes (A) (Figure 3). The EPC2252 has a maximum on resistance (RDS(on)) of 11 milliohms (mΩ), a maximum total gate charge (Qg) of 4.3 nanocoulombs (nC), and zero source-drain recovery charge (QRR).
Figure 4: Shown is the EPC9179 demo board for the EPC2252 GaN FET and other key components. (Image source: EPC)
Figure 2: LiDAR systems combine large numbers of ToF measurements to create 3-D point clouds and images of a target area. (Image source: EPC)
Figure 3: The EPC2252 GaN FET is AEC-Q101 qualified and is suitable for driving laser diodes in automotive LiDAR systems. (Image source: EPC)
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Quick guide to GaN FETs for LiDAR in autonomous vehicles
coefficient (Δλ/ΔT) of 0.25 nm/°C. This quantum-well laser supports rise and fall times of <1 ns with an appropriate driver. The TPGAD1S09H can be used in surface-mount applications and hybrid integration. It can emit light parallel or perpendicular to the mounting plane, and the epoxy resin encapsulation supports low-cost and high-volume manufacturing. The SPL S1L90A_3 A01 from ams OSRAM (Figure 7) is another example of a laser diode that can be used with the EPC9989 interposer board. This single- channel 908 nm laser module can deliver pulses ranging from 1 to 100 ns with a peak output power of 120 watts. It supports an operating temperature range of -40 to +105°C with a duty cycle of 0.2% and comes in a compact QFN package measuring 2.0 x 2.3 x 0.69 mm. For LiDAR systems that require extremely narrow pulse widths, designers can turn to Texas Instruments’ LMG1025-Q1 , which is a single-channel, low-side gate driver with a 1.25 ns output pulse width capability that enables powerful LiDAR systems meeting IEC 60825-1 Class 1 safety requirements. Its narrow pulse width capability, fast switching, and 300 picoseconds (ps) pulse distortion enable precise LiDAR ToF measurements over a long range.
Figure 7: The SPL S1L90A_3 A01 laser diode produces pulses ranging from 1 to 100 ns and can be used with the EPC9989 interposer board. (Image source: ams OSRAM)
Figure 5: The EPC9989 interposer board provides a collection of interposers, such as the SMD laser interposer shown at the top right, that can be snapped off for use with the EPC9179 demo board. (Image source: EPC)
Figure 8: The LMG1025-Q1EVM demo board can accommodate a resistive load representing a typical laser diode for initial setup. (Image source: Texas Instruments)
The development board comes with an EPC9989 interposer board comprising break-away 5 x 5 mm interposers (Figure 5). These correspond to the mounting
A propagation delay of 2.9 ns improves the control loop response time, and the 2 x 2 mm QFN package minimizes parasitic inductance, supporting high- current, low-ringing switching in high-frequency LiDAR drive circuits. The LMG1025-Q1EVM is an evaluation module for the LMG1025-Q1 that has a place to accommodate a resistive load to represent a typical laser diode, or for mounting a laser diode after drive pulse tuning with a resistive load (Figure 8).
Conclusion
Recommended reading Ensure LiDAR Automotive Distance Sensor Precision with the Right TIA Get Started Quickly with 3D Time- of-Flight Applications
footprints of many common surface-mount laser diodes, such as SMD and MMCX, as
Designers are increasingly challenged to develop automotive LiDAR systems that deliver real- time ToF measurements with centimeter resolution that meet the Class 1 safety requirements of IEC 60825-1. As shown, GaN FETs can be used with a variety of laser diodes to produce the nanosecond pulse widths and high peak-power levels needed in high-performance automotive LiDAR.
well as the patterns designed to accommodate RF connectors and a wide variety of other loads. Excelitas Technologies’ TPGAD1S09H pulsed laser (Figure 6), emitting at 905 nanometers (nm), can be used with the EPC9989 interposer board. This laser diode uses a multi-layer monolithic chip mounted on a leadless laminate carrier to provide excellent thermal performance with a wavelength temperature
Figure 6: The TPGAD1S09H pulsed laser produces very high peak pulses and can emit light parallel or perpendicular to the mounting plane. (Image source: Excelitas)
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Article Name retroelectro
Frank J Sprague and the Richmond Union Passenger Railway By David Ray Cyber City Circuits
Inside the city, business and invention would meet over and over again, trying to solve the issue of mass public transportation. One very early example of a solution is the world’s first subway, the ‘London Underground’ sometimes known as ‘The Tube’. Some cities also had ‘street railroad’ systems where a carriage would ride rails, pulled by horses or donkeys, carrying people and goods where they needed to go. According to the census, by 1880, there were over two thousand miles of horsedrawn ‘street railroads’ in America. [1] Multiple times a day, a team of people had to keep the tracks maintained and clean the animal waste off the rails.
1830s-1880s – The problem with public mass transportation
There was a time before the luxury of quick and easy transportation for the masses existed. Transportation was a problem during the mid-nineteenth century. The Second Industrial Revolution was spinning up and the world was quickly becoming industrialized. New manufacturers were emerging, but they needed human labor to operate them. People started leaving their farms to come to the urban centers. Factories and mills were being built faster than the houses and roads needed to support them.
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Eventually, some towns had steam trains that ran a circuit around different areas of their city, allowing people to travel. However, these trains left the areas they drove through covered in smoke and filth. Because of this, most cities forbade steam streetcars in their business and central districts, so they were mainly used in the outer area of a metropolis. [2] Some places, like San Francisco, California, started using ‘cable streetcars’. In this system, a large cable would span the entire length of the railway and it would pull or drag the streetcar along the track. While these were very efficient and clean, the high initial investment made most cities continue to use animal power. Quickly, the convenience of the ‘street railroad’ became a nuisance caused by the pollution.
detailed notebook with 169 pages filled with his inventions and ideas. [3] This period was critical in honing his skills and creativity, laying the groundwork for his future contributions to electrical engineering. Sprague’s notebook included sketches and descriptions of various devices, such as an ‘electric light,’ ‘duplex telephone,’ ‘quadruplex and octoplex telegraph systems,’ a motor, and a means of transmitting facsimiles of pictures by wire. His meticulous documentation of these inventions demonstrates his passion and drive to innovate. Sometime in 1880, Sprague got orders back to Annapolis for examinations, after which he was commissioned as an Ensign. Not long after, he found himself on the USS Lancaster in Europe.
The cars were crowded with hundreds or thousands of people, and the air was full of smoke. The walls of the tunnels were filthy and covered in soot. There are historical cases where people have reported illness after using the Metropolitan Railway, including ‘The Case of Elizabeth Stainsby’ who died soon after traveling in the London Underground. This was one of the only underground subway systems in the world, and imagine that being your first experience.
The dawn of the electric streetcar
The inventor: Frank J Sprague
Toward the end of the nineteenth century, gas-powered trains and streetcars started appearing, but they would bring many of the same problems as their steam-powered counterparts. The electric streetcar was the solution to many of the problems created by steam and animal-drawn streetcars, but it also brought about its own set of challenges and limitations. In 1882, Werner von Siemens developed the first electric trolly streetcar, Elektromote . Essentially an experiment and novelty, the Elektromote operated on a track a third of a mile long for less than two months, from April 29 to June 13, 1882. Following this innovation,
Frank J Sprague was born in Milford, Connecticut, on July 25, 1857. At age 9, his mother, Francis Sprague, died from tuberculosis, and soon after, his father, David Sprague, abandoned his children with Frank’s aunt, Ann Sprague [3]. At an early age, Frank excelled academically. He was fascinated by mechanical devices and electricity and spent much of his childhood building various contraptions, showcasing a talent for engineering. Following High School, his community raised the money needed for him to take an exam in Springfield, Massachusetts, for the US Army’s West Point Academy. However, when he arrived, he found that he had arrived at the testing for the US Naval Academy at Annapolis. Perhaps not bothered by this, he took the exam and joined the Navy as an officer candidate at Annapolis, where he studied mechanics and electricity. [3] After finishing his classes at Annapolis, he was assigned to the USS Richmond as a midshipman. Sprague’s time on the Richmond is an important part of his journey as an engineer and inventor. While serving on the Richmond in the Philippines from May 1879 to February 1880, Sprague kept a
Osgood Ripley Journal | Osgood, Indiana s | Nov 3, 1887
many worked tirelessly over the next several years to produce and market a practical electric streetcar system. By 1888, there were only thirteen electric streetcar systems in America and less than fifty miles of ‘electric street railroad’ were installed nationwide. [2] The opening of the Richmond Union Passenger Railway in 1888 marked a leap in mass transit technology. While there were dozens of attempts before this, it’s opening had the most impact on the industry overall. The first large-scale electric streetcar system officially introduced electric vehicles to the masses. The success of this system in Richmond, Virginia, spurred the adoption of electric streetcars in cities all over America. The electric streetcar allowed cities to grow and become larger centers of industry.
A visit to London, England It was January 1882 when the young Navy ensign took leave in London to visit the Crystal Palace Electrical Exposition. While in London, Ensign Frank J Sprague rode on the world’s first subway. The ‘Metropolitan Railway’ was established in 1863 as an underground train system using coal-powered steam-driven engines.
Cadet Frank Sprague
Werner von Siemens’ Electromote
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and controllable, whether one passenger or twenty, and at the time they were not.
A new era for transportation
1884 – Sprague Electric Railway and Motor Company In March of the following year, 1884, Sprague was awarded patent number 295,454. With the patent, unusual confidence, and unreasonable determination, the 27-year-old man left a promising career working for the ‘Wizard of Menlo Park’ to strike out on his own. From 1884 to 1890, Sprague Electric Railway and Motor Company, sometimes called SERM, focused on building a full- scale electric railway system. While developing his designs and ideas, he worked with other streetcar companies performing repairs and retrofits. This gave him plenty of opportunities to learn the industry quickly, whereas Edison would have kept him engineering power transmission lines. Up to 1888, there had been no less than seventy-four attempts to create a practical electric railway system. [4] Even Edison attempted an electric streetcar with a mile-long track and a car that could go forty miles an hour [3]. The field of ‘electric traction’ was growing at a rapid pace.
1882 - The Crystal Palace Exposition The Crystal Palace Electrical Exposition in London was the largest of its kind. Young Sprague quickly advocated for making himself a judge at the event. He was placed on the judging panel for gas engines, dynamo-electric generators, and electric lamps,
where he first met Edward H. Johnson and Thomas Edison. While aboard the USS Lancaster in France, Frank J Sprague wrote a report about the Crystal Palace Electrical Exposition for the Secretary of the Navy. In this report, he recounts many things he saw as a judge and an observer.’’ Historians tend to agree that this
experience in London shaped the path of his innovation. Without orders on the USS Lancaster, one can wonder if the history of electric transportation would be the same.
1883 – Working for Edison While at the 1882 Crystal Palace Electrical Exhibition, he impressed Thomas Edison and his business partner Edward H. Johnson. So much so that when he resigned his commission with the Navy, he readily found a position at Edison’s Menlo Park in New Jersey. He was placed on the team building power transmission lines in towns and cities. While there, he developed new techniques for building transmission lines. Soon, he found that he could build anything he had in mind. He found a local machine shop and started prototyping the designs that had been stored in his notebooks for many years. While working on this, he came to the realization that he could never rise to the level of Thomas Edison’s glory and wealth while he was working for him. He saw the fame and wealth that came along with being a genius inventor and businessman, and he wanted it. Around this time, in May 1883, he filed for his first patent for the Electro-Dynamic Motor. This motor was novel in that it could keep a constant speed, no matter the load. This was key because a streetcar needs to be predictable
Sprague wanted to be a heroic and famous inventor who got the newspaper's front page, but he knew he could never do that in Edison’s shadow.
“Frank Sprague also attended the 1876 Centennial Exhibition, where Alexander Graham Bell unveiled his invention ‘The Telephone’."
Report on the Exhibits at the Crystal Palace Electrical Exhibition
Sprague stands behind Thomas Edison, Philadelphia 1915
The Crystal Palace of Hyde Park, London
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To this point, most electric systems of the day were only meant to replace the horses with an engine in order to continue using the streetcars that horses once pulled. Sprague was poised to revolutionize the industry with his ‘under-running trolley’ idea. 1888 - Richmond Union Passenger Railway Working with investors and other engineers, the Sprague Electric Railway & Motor Company gained a contract to build an electric streetcar system in Richmond, Virginia. This was noteworthy because of the area's topology. There are reports of the earlier animal-pulled streetcars being called ‘horse-killers’ because of the steep inclines.
West End Railway of Boston Soon after the opening, Sprague met with the head of the ‘West End Railroad’ of Boston, who wanted to install cable cars (like the ones used in San Francisco) in Boston, being skeptical that an electric streetcar could work in a high traffic environment. Sprague rigged the system to prove that his system could operate dozens of cars simultaneously. He instructed the engineers to load slugs in the fuses and increase the generator's power to five hundred volts. [5] Then, with the wave of a lantern, he had twenty-two streetcars on the far end of a line designed for only four streetcars moving along one after another. In his book ‘The Growth of Electric Railways’, he says when they started, the lights all went dim, and the voltage dropped to two hundred volts, but soon all of the cars overcame their initial inertia, and they were soon merrily running along. This test was conclusive, and the fate of the cable in Boston was Settled. From this point, to 1890, some reports say that Sprague had purchase orders for upto two hundred streetcar systems throughout the county.
Earliest type of Sprague motors used in Richmond.
Other electric streetcars couldn’t manage the hilly terrain and steep inclines, while Sprague’s unique design for independent direct drive of each streetcar could. Each streetcar had its own motors underneath the passenger cab. From August 1887 to February 1888, Sprague, with his engineers and laborers, built the Richmond
Union Passenger Railway. When it first opened, the track was twelve miles long and had forty cars, making it the longest electric railway in the world. Each of the forty cars could run independently and navigate the ten-degree inclines through the city. The Richmond Union Passenger Railway included many new innovations. Two of the most pivotal were the ‘trolley pole’ and the ‘trolley wheel’. Before this, electric streetcars would use electrified rails or an overhead wire to carry current. The trolley pole differed in that it would run underneath the overhead wire, making each car easy to remove from the line at any point by simply pulling down the trolley pole. The electric power was produced by a local generation plant, powered by coal and steam.
Example of a competitor’s streetcar by Van Depoele.
Other streetcars of the time would have the motor on the front, with a heavy chain connecting the motor to the axle. Sprague’s design placed the motor underneath the streetcar, connecting it directly to the wheels, delivering more torque and horsepower than any competitor could with a similarly sized motor. All of this came together the Summer of 1888 when the Richmond Union Passenger Railway opened and became the ‘first successful electric railway’ in history. It would continue to operate from 1888 to 1949.
Catalog page from the age selling parts for streetcars.
Sprague’s unique undercarriage motors made the steep inclines a trivial task.
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Beyond streetcars: Sprague’s broader impact on technology In 1890, Sprague Electric Railway and Motor was absorbed by Edison General Electric. It was here when the real problems with Edison started, with Edison removing Sprague’s name and replacing it with the word EDISON. The irony is that he left Edison’s company six years earlier to avoid this exact thing from happening. Sprague’s wife, Harriet Sprague, writes about this experience in her book ‘Frank J Sprague and the Edison Myth,’ some years after his death.
his legacy has been shadowed by Thomas Edison, but many of his inventions and techniques are still used today in freight trains and elevators worldwide. Sprague raised a family that returned to North Adams, where his son Robert C. Sprague started Sprague Electric Company. Sprague Electric became renowned for its innovation in electronic components, particularly tantalum capacitors. In the 1960s, his son, John L. Sprague, became more involved and directed the company towards the new world of semiconductors, where it was successful for many years. Suggested reading Engineering Invention: Frank J. Sprague and the U.S. Electrical Industry by Frederick Dalzell The Mechanization of Urban Transit in the United States by Eric Schatzberg Report on The Exhibits at the Crystal Palace Electrical Exhibition by Frank J. Sprague American Experience: The Race Underground Frank J Sprague and the Edison Myth by Harriet Sprague Frank J Sprague: Seventy-Fifth Anniversary Richmond Union Passenger Railway IEEE Milestone Listing The Growth of Electric Railways by Frank J Sprague
References [1] "Report on Transportation Business in the United States at the Eleventh Census," U.S Government Printing Office, Washington, DC, 1894. [2] E. Schatzberg, "The Mechanization of Urban Transit in the United States," in Technological Cpmpetiveness (Ed: William Aspray), IEEE Press, 1993. [3] F. Dalzell, Engineering Invention: Frank J. Sprague and the U.S. Electrical Industry, Cambridge, Ma: The MIT Press, 2010. [4] "IEEE Milestones: Richmond Union Passenger Railway, 1888," [Online]. Available: https://ethw.org/ Milestones:Richmond_Union_Passenger_ Railway,_1888. [Accessed 2024 07 21]. [5] F. J. Sprague, The Growth of Electric Railways, Atlantic City, NJ: American Electric Railway Association, 1916.
Frank J Sprague is born in Milford Connecticut July 25, 1857
1866 Mother dies and he moves to North Adams, Massachusetts 1876 The Centennial Exposition in Philadelphia
1874 Sprague starts attending the Naval Academy in Annapolis, Maryland. 1878 - 1880 Sprague leaves Annapolis and is assigned to the USS Richmond.
1881 - 1883 Serves on the USS Lancaster in Europe
1882 Served on the Jury at the 1882 Crystal Palace Exposition in London
1883 Left the Navy to Work for Edison
May 1883 Files First Patent Application – Dynamo-Electric Motor • Patent Link
1884 Leaves Edison to Start the Sprague Electric Railway & Motor Company
After feeling bamboozled by Edison, he decided to leave the streetcar business altogether—for a while anyway. He would continue changing the world by developing the first practical electric elevator, regenerative braking, and electric locomotives. In 1906, he was responsible for electrifying New York’s Grand Central Terminal lines. Many consider Frank J. Sprague to be one of the most influential inventors of the nineteenth and early twentieth centuries. Unfortunately,
1886 Invents Regenerative Braking
1888 Opens the Richmond Union Passenger Railway (Twelve Miles in Length with Forty Cars) 1890 Sells to Edison General Electric
1890 Contracts 200 Trolley Systems
Sprague Legacy: Electrical Inventions and Innovation
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How to use residual current monitors to ensure electrical safety when charging electric vehicles By Jens Wallmann Contributed By DigiKey's European Editors
Power electronic circuits such as rectifiers, switching converters, frequency inverters, along with inverter and phase-angle control systems, have a wide variety of load current characteristics. The resulting potential residual currents are categorized as sinusoidal AC, pulsed DC, and straight DC. These residual current forms are dangerous to humans. Table 1 shows typical load current signals of various circuit topologies and the resulting residual current waveforms. Columns 1 to 3 assign RCD types suitable for detection.
Frequent charging of the high- voltage battery of electric vehicles (EVs) translates to high mechanical stress requirements for charging cables and connectors. If the insulation breaks and live metal parts are exposed, or shunts appear in the onboard electronics, life-threatening residual currents can occur in the EV user’s body. Particularly problematic are various DC residual current forms that cannot be detected by the AC- sensitive Type-A residual current devices (RCDs). To prevent electric shock accidents, manufacturers of EV supply equipment (EVSE) must incorporate RCDs into their power electronics products that trip within a few milliseconds for both AC and DC residual currents of a few milliamperes (mA). This article explains forms of residual currents, how to measure them, and where to install the RCD in the charging circuit. It then introduces residual current monitors (RCMs) from Littelfuse that system designers can use to add protection against DC electric shock in their EVSE devices in a cost and time-efficient manner. The article also demonstrates which EV charging modes these current sensors are suitable for and how they are used.
Residual currents in the EV charging circuit Charging EVs at voltages up to 400 volts AC and 1000 volts DC requires extensive protective measures for the EV user when handling charging equipment. Due to the harmonic-rich and asymmetric switching pulses of charging stations and onboard chargers, as well as several hundred volts of DC link voltage, various types of AC and DC residual currents can occur via shunts, coupling effects, insulation faults, and leakage faults.
Table 1: Fault current forms and their detection according to the type of RCD that is most suitable (columns 1 to 3). (Image source: Wikipedia)
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How to use residual current monitors to ensure electrical safety when charging electric vehicles
thresholds in the EV charging circuit are 6 mA DC and 30 mA AC. System designers can now easily implement specific personal protection requirements in the charging circuit by selecting an RCD type of the appropriate standard. Table 2 lists residual current forms and trip tolerance of the different RCD or ground fault circuit interrupter (GFCI) types.
The IEC 62196 standard, therefore, defines two residual current protection options: the use of an all-current sensitive RCD of Type B (or Type B+), or an RCD of Type A in conjunction with a residual DC monitoring system according to IEC 62955 with IΔn DC ≥ 6 mA. The DC fault current monitoring can be arranged in the wall box, in the building electrical installation, or at both locations. Since an AC-sensitive Type-A or Type-F RCD is usually present in building electrical systems, designers can cost-effectively add 6 mA residual DC monitoring to Mode 3 wall boxes or charging stations, as well as to the in-cable control boxes (ICCB) of Mode 2 charging cables (Figure 1, cases 2 and 3). Charging modes for EVs The EV battery can be charged via different charging modes, depending on the available on-site power connection, connection plug, charging cable, and the charging technology installed in the vehicle, as well as in the charging station. In Europe, the electrical energy can be fed into the vehicle via single- phase AC (230 volt/3.6 kilowatt (kW), three-phase AC (400 volts/22 kW), or via high-voltage DC charging stations (up to 1000 volts DC/500 kW). Figure 2 illustrates the four charging modes defined in the IEC 61851 standard.
Installing RCDs in the EV charging circuit Type-A or Type-F RCDs only detect AC residual current and DC pulsating current, which is insufficient for protecting an EV charging circuit. A wide range of straight DC residual currents that can occur in the onboard charger or battery management system must also be considered.
Tripping characteristic of RCD types In general, personal protection against electric shock on electrical installations is regulated by IEC 60479 and UL 943. Both standards define significant AC and DC residual currents in the range of 6, 30, 100, 300, 500, and 1000 mA, at tripping times ranging from 20 to 500 ms. Common tripping
Figure 1: EVSE devices must add a DC RCM downstream of the AC-sensitive Type-A RCD (case 2), or have one connected to AC mains directly via a Type-B RCD (case 4). (Image source: goingelectric.de)
Table 2: Tripping characteristics of different GFCI or RCD types. (Table source: abb.com)
Figure 2: Illustration of the four charging modes defined in the IEC 61851 standard. (Image source: bestchargers.eu)
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How to use residual current monitors to ensure electrical safety when charging electric vehicles
Mode 1 (single-phase AC charging up to 3.6 kW; default mode of charging) In this case, the electric or hybrid vehicle is connected to a standard 230-volt household socket using a simple passive cable and will be charged using low power at a maximum of 3.6 kW via the onboard charger. This charging scenario does not provide sufficient protection against residual DC for the user. Usually, only an AC- sensitive Type-A RCD is installed in the building's electrical system.
Mode 2 (single/three-phase AC charging up to 22 kW via an ICCB charging cable) A Mode 2 charging cable equipped with a Type 2 vehicle plug contains an ICCB that performs safety and communication functions when charging EVs using domestic and three-phase sockets to prevent overloading them. The following protection functions must be integrated with the ICCB: ■ Determination of polarity and protective conductor (PC) monitoring; only a few ohms of loop impedance are permitted between neutral and the PC.
■ Testing of the electrical connection between the PC and the metal body. ■ An AC and DC residual current circuit breaker prevents current accidents. ■ Monitoring/shutdown of the charging process in the event of anomalies (for example, current fluctuations due to corroded plug contacts or cable breakage). ■ Monitoring of the temperature inside the ICCB and both plugs and perform shutdown if necessary.
■ Control of the charging power: Pull-down resistors on the control pilot (CP) wire to signal the cable current load rating to both the wall box and the EV; the pulse width modulation (PWM) signal on the charging control (CC) wire signals the wall box charging power capability to the EV. Mode 3 (single-phase/three- phase AC charging up to 22 kW via wall box) For EV charging, a passive Mode 3 cable is connected to a wall box in private households or a public AC charging station in parking lots. Both have integrated the same protection functions as the ICCB above. Mode 4 (direct battery DC fast charging up to 500 kW) DC high-power charger (DC/HPC) stations for EVs deliver significantly higher charging currents compared to Mode 2 and Mode 3. Shock protection from residual AC and DC is implemented in this supercharger; the different charging cables are always firmly attached. Measure AC and DC fault currents in the EVSE circuit RCMs, from the RCM14 series from Littelfuse Inc., detect DC and/or AC residual currents in AC or DC systems and deliver an
Figure 3: If a fault current (I g ) flows into the ground potential via the human body, the GFCI total current differs from zero, and the circuit breaker trips. (Image source: Littelfuse)
output signal to control an external disconnect (cutoff relay). In contrast, RCDs and residual current circuit breakers (RCCBs) have an integrated cutoff relay. AC residual currents are detected using an inductive current transformer (CT). For this purpose, the current forward conductor (IL) and current return conductor (IN) are fed through a soft magnetic toroidal core, causing both current vectors to normally compensate for each other and add up to zero. If a fault current (I g ) flows into the ground potential via the human body in the circuit behind the detector, the RCM or GFCI total current differs from zero, and the circuit breaker trips (Figure 3).
By integrating a fluxgate magnetometer probe into a slot of the toroidal core and compensating the magnetic flux to zero by means of a compensation coil, the CT can also detect differential DC. More accurate than Hall effect sensors or shunt resistors, this method detects tiny DC fault currents from 6 mA at heavy DC load currents up to 500 amperes (A). RCMs featuring control output for disconnector Littelfuse’s RCM14 series is ideal for use in ICCB charging cables for EVs (Mode 2) and EV charging stations (Mode 3). They are available in three residual current detection options in accordance
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