POWER ELECTRONICS QUIZ by ELECTRICAL ZINDAGI
Table of Contents
Power Electronics — Quick Search-Focused One-line Topics & Tricks
(Each entry is written to match common search intent and provide a quick trick or familiar example — presented in colorful 3D blocks.)
Power electronics basics — Understand converters vs. inverters: converters change AC↔DC while inverters create AC from DC — trick: follow the arrow of power flow, not the signal name.
Turn ratio of transformers — Use N1/N2 = V1/V2 quickly: if primary is 1000 turns and secondary 200, voltage scales by 5× — memory tip: "turns turn volts".
DC-DC converters (buck/boost) — Buck reduces voltage, boost raises it; test mentally with battery examples: 12V→5V is buck, 5V→12V is boost.
Rectifiers & diodes — Full-wave bridge produces smoother DC than half-wave; trick: add a capacitor to the bridge to see the difference instantly on a scope.
Thyristor (SCR) basics — Latch behavior: once gated, SCR conducts until current drops below holding value — quick check: use series lamp to watch unlatch.
Pulse Width Modulation (PWM) — PWM controls effective voltage by duty cycle: 50% duty ≈ half RMS; practical: dim an LED with PWM to feel the effect.
Inverter topologies — Single-phase vs three-phase inverters: for motors use three-phase for smoother torque; mnemonic: "more phases = smoother rotation".
IGBT vs MOSFET — Use MOSFETs at high switching freq and low voltage; IGBTs excel at high-voltage, medium-frequency switching — shortcut: MOSFET = speed, IGBT = strength.
SMPS essentials — Switching regulators are smaller and efficient compared with linear regulators; remember to add EMI filters near the input to reduce noise.
Power factor correction (PFC) — Active PFC shapes input current to be sinusoidal; trick: if your equipment draws weird harmonics, measure PF and then add PFC stage.
Harmonics & THD — Total harmonic distortion reduces efficiency and may overheat transformers; test by observing odd harmonics (3rd, 5th) on spectrum analyzer example.
Snubber circuits — Use RC or RCD snubbers across switches to limit dv/dt and protect semiconductors; try small RC across MOSFET in lab to see ringing drop.
Gate driving techniques — Proper gate resistor and driver reduce switching losses and ringing; rule: faster edges = lower switching loss but more EMI — balance with RC.
Thermal management — Heatsinks + thermal paste reduce junction temperature; quick method: measure case temp under load then double-check with improved cooling.
Switching losses calculation — Psw ≈ 0.5·V·I·tsw·fs — use a calculator or spreadsheet to estimate switching loss early in design to size heatsinks correctly.
Soft-start & inrush limiting — Use NTC or pre-charge resistor for capacitive loads in rectifiers; simple classroom demo: add NTC to a big electrolytic bank and note start current drop.
Phase-controlled rectifiers — Use SCR firing angle control to regulate DC output; memory trick: later firing angle → lower DC average.
Bidirectional converters — Needed for battery-to-grid or regenerative braking systems; think "both arrows" for charging and discharging control strategies.
Isolation & safety — Isolation transformers and optocouplers prevent dangerous common-mode faults; simple test: always start by checking isolation resistance before student experiments.
EMI filtering basics — Use common-mode chokes and Y capacitors to reduce conducted EMI; tip: place filters as close to the input as possible on the PCB.
Snubber and clamp selection — TVS diodes, RCD clamps and RC snubbers each solve different overvoltage problems; pick TVS for spikes, RCD for energy dissipation.
Current sensing techniques — Shunt resistors, Hall sensors and current transformers each trade accuracy vs isolation; quick guide: use shunts for low-value accurate DC sensing.
Control loops & stability — PI/PID control is common in power supplies; hint: slow integral avoids oscillation; test with step changes to verify settling time.
Protections (OCP/OVP/OTP) — Design overcurrent, overvoltage and overtemp protections into supply; simple demo: induce a short through a current-limited supply to observe OCP action.
Energy efficiency metrics — Use efficiency (%) = Pout/Pin and always evaluate at typical load (not just full load); trick: log a few load points to get real-world efficiency curve.
DC link capacitors — Choose low-ESR caps for high ripple currents; visual tip: film caps survive longer under ripple than electrolytics in many SMPS designs.
Isolation ratings & creepage — For mains designs, always check creepage/clearance distances on PCB to meet safety standards; rule of thumb: larger clearance for higher voltages.
Design for manufacturability — Keep test pads for gate, drain, source and sense lines to speed up production testing; helper: label pads clearly in silkscreen.
Basic troubleshooting steps — Start with visual inspection, measure passive values, then power-on tests with current limits; tip: use a series lamp for safe bench testing.
Practical exam tips — Learn formulas (turn ratio, duty cycle, RMS), memorize common component values, and practice sketching waveforms for rectifiers and inverters.
Real-life examples — EV charger inverter, SMPS phone charger, and grid-tie inverter share the same blocks; remember by mapping real product → block diagram.
Quick revision checklist — Key items: transformer turns, duty cycle, switching freq, snubber, gate resistor, thermal path, and protection thresholds — tick them in any design review.
Study trick — Convert problems into energy flow diagrams and label losses; learn to estimate losses (~10–30% in some legacy designs) then iterate on improvements.
Mock-quiz challenge — Create 10-min quizzes focusing on turn ratio, PWM duty-to-voltage, and rectifier outputs to boost recall under exam conditions.
Career pointers — Learn power device datasheets, thermal modeling and EMI; employers love candidates who can prototype and explain tradeoffs with simple demos.
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