Electrical Engineering Circuit Analysis

EeroQ researchers published new findings in Physical Review X about controlling individual electrons at temperatures above 1 Kelvin. Here's what they accomplished: Current quantum computers operate near 10 millikelvin. EeroQ demonstrated electron control at temperatures 100 times higher. Their approach uses electrons floating on superfluid helium, integrated with standard superconducting circuits. Why this matters for quantum computing: → Reduces extreme cooling requirements   → Uses existing quantum hardware infrastructure   → Creates a cleaner environment for qubit operations   → May help with scaling challenges Johannes Pollanen, EeroQ's cofounder, noted this "reduces a key barrier to scalable quantum computing." The company has been developing this electron-on-helium technology since 2017. The work validates theoretical predictions about using helium as a platform for quantum operations. The research addresses a practical problem: current quantum systems require expensive, complex cooling to near absolute zero temperatures. For those working in quantum computing: What cooling challenges do you face in your systems? ♻️ Repost to help people in your network. And follow me for more posts like this.

Your power converter is hitting efficiency limits. But what if the problem isn't your design - it's your semiconductor choice? Most engineers still default to silicon MOSFETs because "they've always worked." Yet these devices are bumping against fundamental physics barriers that no amount of clever engineering can overcome. While silicon MOSFETs max out around 500 kHz switching frequency, gallium nitride devices can push beyond 10 MHz. That's a 20x improvement, enabling smaller inductors and higher power density. The numbers tell a compelling story. In a head-to-head comparison using 400V, 15A devices: • At 200 kHz switching frequency, silicon devices show 40W power loss • SiC devices hit 15W loss at the same frequency   • GaN devices achieve just 8W loss—an 80% reduction from silicon Power factor correction converters, solar inverters, and DC-DC systems all benefit from higher switching frequencies. You can shrink those bulky inductors and transformers that dominate your board real estate. GaN devices need only 22% of the gate charge required by equivalent silicon devices. Less gate charge means faster switching transitions and lower driver power consumption. I used to think GaN was just expensive silicon with better marketing. The cost analysis changed my mind. Yes, individual GaN devices cost more upfront. But when you factor in smaller magnetics, reduced cooling requirements, and higher system efficiency, the total cost equation often favors GaN. The adoption curve reminds me of when MOSFETs displaced bipolar transistors in the 1980s. Initially expensive and exotic, but eventually became standard because the performance advantages were undeniable. Solar installations particularly benefit from this technology. Higher switching frequencies enable smaller filter components while efficiency gains directly boost energy harvest. In data centers, every percentage point of efficiency improvement translates to significant operational savings. What surprised me most was the reverse conduction capability. Unlike silicon MOSFETs that rely on body diodes with recovery losses, GaN devices can conduct in reverse without these penalties, eliminating dead time losses. The manufacturing approach also matters. While SiC requires expensive substrates, GaN devices grow on standard silicon wafers using existing fab infrastructure. This manufacturing advantage should drive costs down faster than expected. Recent developments in isolated gate drivers are addressing adoption barriers. Solutions like those from Allegro MicroSystems integrate bias supplies directly into the driver, eliminating external power rails and simplifying system design while reducing EMI. For engineers working on next-generation clean energy systems, the question isn't whether to consider GaN—it's whether you can afford not to. What's been your biggest challenge in improving power conversion efficiency in clean energy applications?

In the prior post, we discussed what reactive power is. Where does the reactive power from SVCs (Static Var Compensator) and voltage-source converters such as STATCOMs (Static Synchronous Compensator) come from?   Before we get there, first we need to discuss how energy is stored in reactive elements, such as inductors and capacitors. We also need to have an image of how it flows in a power system.   For inductors, it is stored in magnetic fields. Inductance is a function of physical and material properties. The current in an inductor cannot change instantaneously. The energy is a function of the current flowing through the inductance, where E = 1/2*L*I^2.   For capacitors, it is stored in electric fields. Capacitance is a function of physical and material properties. The voltage across a capacitor cannot change instantaneously. The energy is a function of the capacitor voltage, where E = 1/2*C*V^2.   What about the flow of reactive power in AC systems, where does it go? Reactive power flows “downhill” from higher voltage magnitude to lower voltage magnitude. This can either be directly influenced by the addition of shunt capacitors and reactors (as is the case for SVCs), or the AC line voltage at the voltage-source converter output can be synthesized to either greater (capacitive/over-excited output, increasing voltage) or less (inductive/under-excited output, decreasing voltage) than the system voltage, allowing direct control of Q (as we’ll see in the next post).   Do AC capacitors and inductors of SVCs provide the reactive power? They sure do, and it's dependent on how open the "valve" is for its active elements (such as Thyristor Controlled Reactors or Thyristor Switched Capacitors), determined by the delay angle of the thyristor valve firing. This regulates the voltage these impedance elements experience (V=I*Z, or V=I*X when considering reactance), thereby changing the amount of reactive current produced. When these valves are fully "open" (visualize a water valve, instead of thyristor valve), these elements are (essentially) directly connected. Reactors in series with these valves also ensure the power electronics are protected from high-frequency transients. For harmonic filters contained within SVCs, these also provide reactive power dependent on their impedance elements, but the voltage they experience is not controllable. The capacitance of a harmonic filter is predominantly responsible for the Mvar and the inductance is predominately responsible for the tuned frequency of resonance. As reactive current is proportional to voltage for a given reactance, SVC capability to provide reactive power is proportional to voltage squared (Q=V^2/X).   Up Next – How reactance is used in STATCOMs (as well as other voltage-source converters).   #PowerSystems #PowerElectronics #ControlSystems #Modeling #SystemStudies #RenewableEnergy #ReactivePower #FACTS #SVC #STATCOM

GaN is not always better than silicon. Below about 500kHz, an optimised silicon MOSFET pair can match or beat GaN on total losses, while being significantly simpler to design around. The reason comes down to what dominates your losses at different switching frequencies. GaN's advantage is almost entirely in switching loss: near-zero Qrr, very low Qgd, negligible Eoss. At 1MHz these parameters matter enormously because you're paying the switching loss penalty a million times per second. At 200kHz you're paying it five times less often, and the gap shrinks proportionally. Meanwhile, conduction loss doesn't care about switching frequency. It depends on RDS(on) and duty cycle. And the best silicon MOSFETs in a given package often match or beat GaN on RDS(on) because silicon process technology is decades more mature at a given voltage class. For a 12V-to-1.8V, 20A converter, an optimised silicon pair (low-Qgd part on the high side, low-RDS(on) part on the low side) dissipates 3.63W at 500kHz. A pair of EPC2045 GaN FETs dissipates 3.42W. That's a 0.21W saving from GaN, about 0.6% efficiency, in exchange for a dedicated GaN gate driver with tight voltage tolerance, no avalanche rating (so tighter layout requirements), and all heat exiting through solder bumps into the PCB. Below 450kHz the silicon pair actually wins because switching losses shrink while conduction losses stay constant. Above 1MHz, GaN pulls away decisively. GaN makes sense at high frequency, tight thermal constraints, or when you need the smallest possible footprint. But if you're switching at 200-400kHz with reasonable board space, optimised silicon is simpler, cheaper, and just as efficient. The industry narrative that GaN is always the better choice doesn't always necessarily hold up. With the work I've been doing to bring real component curves into swtichmode.io, I will be looking at expanding this trade off further. Full worked comparison with loss breakdowns on the switchmode.io blog (link in comments). #PowerElectronics #GaN #MOSFETs

LSIG Protection in Air Circuit Breakers (ACB) 1. L – Long-time protection Protects cables and equipment from sustained overloads. Adjustable pickup (0.4–1.0 × In) and delay (up to 24s at 6×Ir). 2. S – Short-time protection Deals with short circuits below the instantaneous range. Includes a time delay for coordination with downstream devices. Option for I²t ON (thermal mimic curve) or I²t OFF (faster clearing). 3. I – Instantaneous protection Trips without delay on high-magnitude faults (busbar faults). Ensures quick disconnection to protect the system. 4. G – Ground fault protection Detects earth leakage/ground faults often missed by phase protection. Adjustable pickup (typically 0.2–0.6 × In) with a short delay. Short-circuit current (approx): Example 1250 kVA, 11/0.415 kV transformer, 6% Z: FLC ≈ 1739 A Short-circuit current ≈ 29 kA Typical ACB LSIG Settings L: 1440 A, delay 12s S: 7200 A, delay 0.2s, I²t ON I: 19.2 kA, no delay G: 480 A, delay 0.2s 🔹 Advantages ✔ Complete protection (overload, short circuit, ground fault) ✔ Flexibility & coordination with downstream devices ✔ Enhanced reliability & safety ✔ Monitoring, event logs, and ZSI (in advanced trip units) 🔹 Disadvantages ✘ Needs proper studies & setting coordination ✘ Longer delays = higher arc-flash energy ✘ Higher cost & complexity than LI units ✘ Requires periodic testing LSIG protection ensures comprehensive safety, selectivity, and reliability in LV power distribution. The key is correct setting & coordination—always verify with TCC curves, cable ampacities, and downstream breaker data. Standards for LSIG Protection in ACBs IEC 60947-2 – Low-voltage circuit breakers (defines performance, trip units, and protection settings for ACBs). IEC 60364 / IS 732 – Electrical installations in buildings (protection against overcurrent, short circuit, and earth faults). IEC 60947-4-1 – Contactors & motor-starters (relevant for coordination with downstream feeders). IEEE 242 (Buff Book) – Protection and coordination of industrial & commercial power systems. ACBs & LSIG trip units are tested and certified as per IEC 60947-2 (and IS/IEC 60947-2 in India). Coordination studies (selectivity, discrimination, arc-flash) often follow IEC 60364, IEEE 242, and utility-specific codes. #ElectricalEngineering #PowerSystems #Protection #ACB #LSIG #Safety

Understanding LSIG Protection in ACB (Air Circuit Breaker) In modern LV power distribution systems, protection is not just about tripping — it's about selectivity, reliability, and system stability. The LSIG protection functions in an ACB play a critical role in achieving this. Let’s break it down L – Long Time Protection (Overload): Protects against sustained overcurrent conditions. Adjustable current (Ir) and time delay Prevents nuisance tripping during inrush (e.g., motors, transformers) S – Short Time Protection: Handles short circuits with intentional delay. Ensures selectivity with downstream breakers Uses I²t characteristics for coordination I – Instantaneous Protection: Trips immediately under severe fault conditions. No intentional delay Protects system from high fault currents G – Ground Fault Protection: Detects leakage or insulation failure. Protects equipment and prevents fire hazards Adjustable pickup and delay for coordination The curve shown represents the time-current characteristics, where: Vertical axis. --- Time (log scale) Horizontal axis. --- Current (log scale) Different regions define how the breaker responds under various fault conditions Proper LSIG setting ensures: Selective tripping (only faulty section isolates) Equipment protection System continuity Safety of personnel A well-coordinated LSIG curve is the backbone of any reliable LV protection system. #ElectricalEngineering #PowerSystem #Power #CB #Relay #OCProtection #Protection #Switchgear #ACB #LSIG #ElectricalSafety #EngineeringLife

💡 Ever wondered how firing angle impacts your rectifier's DC output? When it comes to power electronics, controlling the output isn’t magic — it’s all about timing. 🎯 Meet: The Single-Phase Full-Wave Controlled Rectifier Using thyristors, this circuit allows us to delay conduction and control the average DC output precisely. ⚡ But how does it work? A simple adjustment in the firing angle (α) changes the entire game. 👇 Quick Breakdown: ✅ Firing Angle = 0° → Thyristors conduct from the start → Max DC output ✅ Firing Angle = 45° → Mid-conduction → Reduced DC output ✅ Firing Angle = 90° → Peak-conduction only → Low DC output ✅ Firing Angle = 135° → Barely any conduction → Very low DC output 🔧 The result? The more you delay the thyristor triggering, the lower your output voltage becomes. 💡 Engineer's Insight: → This principle powers motor speed control, soft starters, and even HVDC converters. 📊 Visualization is the key! That’s why I created this simulation-style GIF — so you can “see” theory in action. 💬 What other power electronics topics would you love to see visualized next? Let’s make complex concepts simple, one diagram at a time! ♻️ Repost to share with your network if you find this helpful. 🔗 Follow Ashish Shorma Dipta for posts like this. #PowerElectronics #Rectifier #Thyristors #LearningMadeSimple

Introduction to Air Circuit Breaker (ACB): An Air Circuit Breaker (ACB) is a low voltage protective device used in power systems to control, protect and isolate electrical circuits. It uses air as the arc quenching medium. ACBs are designed to make, carry and break current under normal as well as fault conditions such as overload, short circuit and earth fault. They are widely used in industries, substations and commercial buildings due to their high breaking capacity, reliability and safety. Working Principle of ACB: The working of an ACB is based on fault detection and interruption of current. Under normal conditions, current flows through closed contacts. When a fault occurs, the trip unit senses the abnormal condition and sends a trip signal. The operating mechanism opens the contacts, and an arc is formed. This arc is extinguished by air in the arc chamber, interrupting the current flow and protecting the system. Construction of ACB: An ACB consists of various components such as main contacts, arcing contacts, arc chute, operating mechanism, trip unit and control circuit. These parts work together to ensure safe and efficient operation. The breaker can be of fixed type or drawout type depending on application. Main Components: The main components include control terminals, electronic trip unit, operating mechanism, closing spring, spring charging motor, arc chamber, main contacts, moving contacts and insulating frame. Each component plays a specific role in operation and protection of the breaker. Arc Chamber (Arc Chute): The arc chamber is responsible for extinguishing the arc formed during contact separation. It splits the arc into smaller parts, cools and de-ionizes it, ensuring safe interruption of current. Contacts in ACB: ACB uses two types of contacts – main contacts and arcing contacts. Main contacts carry current in normal condition, while arcing contacts handle arc during opening and protect main contacts from damage. Operating Mechanism: The operating mechanism uses stored energy in springs to open or close the contacts quickly. The spring charging motor charges the spring automatically, ensuring readiness of the breaker. Trip Unit in ACB: The trip unit is the brain of the ACB. It detects abnormal conditions such as overload, short circuit and earth fault. It processes the fault information and sends a trip signal to open the breaker. Modern trip units are microprocessor-based and provide adjustable protection settings, monitoring, communication and high accuracy, ensuring reliable and safe operation of the power system.

Operational amplifiers (op-amps) are powerful components used in many signal-processing applications. By simply changing the feedback elements, the same op-amp can perform different mathematical operations on electrical signals. 🔹 Inverting Amplifier The signal enters through a resistor into the inverting input. The output is amplified and phase-shifted by 180 degrees. The amplification level (gain) depends on the ratio between the feedback resistor and the input resistor. For example, if the ratio is 5:1, the output becomes five times larger but inverted. 🔹 Integrator Circuit When a capacitor is placed in the feedback path, the circuit integrates the input signal over time. A square wave input will produce a triangular wave output. The rate of change depends on the RC time constant. 🔹 Logarithmic Amplifier By using a diode or transistor in the feedback loop, the output voltage becomes proportional to the logarithm of the input signal. This is especially useful for audio signals or sensors that operate over a wide dynamic range. 🔹 Transimpedance Amplifier This configuration converts input current (such as from a photodiode) into a voltage output. The output voltage equals the input current multiplied by the feedback resistor value. These examples show how versatile an op-amp can be — small changes in the feedback network completely change the function of the circuit.

🔍 Not every fault in a power system is the same — and neither should the response be. ⚡ Differential Protection Relays – The Intelligent Shield of Electrical Assets When it comes to protecting transformers and other critical equipment, even a fraction of a second can decide whether the system keeps running smoothly or suffers a major failure. This is exactly where differential relays prove their value. By constantly monitoring and comparing the current at the input and output of protected equipment, they make rapid decisions on whether action is required. 💡 Their behavior under different scenarios: ✅ Normal Operation Incoming current equals outgoing current. No tripping is needed, and equipment remains in safe operation. ⚠️ External Faults The disturbance occurs outside the protected zone. Relay stays stable and avoids unnecessary tripping. 🚨 Internal Faults Current entering does not match the current leaving. Relay issues an immediate trip command to isolate the faulty section and safeguard the equipment. 👉 The brilliance of differential protection lies not in the magnitude of the fault current but in where the fault takes place. 💭 Have you ever witnessed a differential relay in action protecting a transformer? I’d love to hear your experience in the comments. 🔄 If you found this useful, feel free to share it with your network. #PowerSystems #ProtectionSystems #SubstationAutomation #TransformerProtection #DifferentialRelay