Power (not only semiconductor) converters

Power semiconductor converters Equipment for changing quality of electrical energy (voltage, current, frequency, no. of phases, impedance, etc Conversion of energy „nearly“ without power losses The most often converters: –rectifiers (diodes, not controlled) –frequency converters (non-direct, with DC link) The most often applications: –Power supply, AC drivers

History of converters electro-mechanical principle –beginning by Tesla and Edison –rotating rectifiers, switching of windings, brushes electro-magnetic principle –groups of machines: Ward-Leonardo AC vers. DC end of 19th. century

Selenium based rectifiers: –end of 19. century, low currents Mercury based rectifiers: –current of ions in a steam of Hg –Cathode – liquid of Hg, Anode – solid –range of kA, kV, traction power supply –In Prague from 1929 since 1967 Thyratrone – units of kV, units of A History of converters Siemens 15 kV / 1A

Semiconductor converters In Czech from the end of 50. ČKD Elektrotechnika In 1964 introduced ČKD Polovodiče – Pankrác discrete devices modules converters silicon heat sinks, accessories

Converters - overview rectifiers: AC/DC inverter: DC/AC Frequency converter: AC/AC (direct/indirect) DC converter: DC/DC AC – effective DC - average

Most often converters - SMPS SMPS – Switch Mode Power Source all chargers, PC supplies, household appliances Aim – reducing of mass and dimension of transformers in comparison with classic linear power supply Product S·B · N stands for a cubic (volume) of transformer

Most often converter- DC supply

Power supply for industry DC sources Without PFC Active PFC Power factor correction – better efficiency passive – big choke (coil) active – adapted DC link, better PF, more expensive

4.1 Charakteristika vysokofrekvenčního rušení Example of high frequency disturbance - SMPS Basic blocs of SMPS and frequency spectrum Disturbance /noise voltage/ of brush DC driver

4.3 Šíření rušení po vedení Noise-suppressing filters (EMC) – basic circuit solution symmetric and asymmetric voltage – more types of L, C impedance miss-matching = low efficiency reducing of mass and dimensions of coils limits for capacitors Cx/Cy = leakage currents additional functions = surge protections, switches, etc.

4.3 Šíření rušení po vedení Assembly and mounting of filters placing and mounting of filters = influence of efficiency separating of input/output, no loops, minimizing of lengths/areas placing directly at input good connections between chassis and filters (grounding) YES NO NO NO YES

4.3 Šíření rušení po vedení EMC chokes – most simple solutions connected in series in lines rated for nominal current overdosing of cores (not convenient) compensated chokes –Subtraction of magnetic fluxes –Not efficient for symmetrical voltage not-compensated chokesCurrent compensated chokes

Nízkofrekvenční a přechodné rušivé jevy Harmonic, inter-harmonic current Immediate power p V·AProduct of immediate V and I Apparent power S V·AProduct of effective V and I Active power P WAverage value of immediate power p (for periodical signals) Non-active power Q~Q~ V·A, varSquare root of difference between S and P (just for periodical conditions) Reactive power Q V·A, varNon active power for linear double-pole device (R, L, C) Power factor -general definitions: P/S cos  - Just for harmonic signals is P/S equal to cos  ! Phase angle  °, radAngle from voltage to current vector Definitions according ČSN IEC : Basic circuit theory

Nízkofrekvenční a přechodné rušivé jevy Typical currents - consumption Harmonic conditions: Non-harmonic conditions: voltage current voltage current

Nízkofrekvenční a přechodné rušivé jevy Power triangle, power factor Harmonic conditions: linear devices (R, L, C) sinusoidal current General non harmonic conditions: nonlinear devices (etc. rectifiers) general consumption of current

Nízkofrekvenční a přechodné rušivé jevy Deformation and displacing of current/voltage waveforms Deformation only of current waveformDeformities of voltage and current waveforms (simultaneously) voltage current voltage current

Nízkofrekvenční a přechodné rušivé jevy Influence of higher Harmonics components creation of non-active power, increase of apparent power it makes power factor worse it makes bigger power losses increase of loading for compensation capacitors increase of pulsing moments (AC drivers) higher harmonics currents are not compensated (neutral conductor!!!) overloading of neutral conductor

Nízkofrekvenční a přechodné rušivé jevy Reducing of harmonics currents (components of current) PFC – Power Factor Correction (removing of root cause) compensations (passive/active filters) – removing of consequences principle of PFC – prolongation of current consumption (chokes) passive PFCactive PFC

Nízkofrekvenční a přechodné rušivé jevy Passive PFC Consumption of current – time dependence Spectrum of harmonics voltage current

Nízkofrekvenční a přechodné rušivé jevy Active PFC Consumption of current – time dependence Spectrum of harmonics voltage current

Nízkofrekvenční a přechodné rušivé jevy Filters for compensation Passive filters: resonance LC circuits for actual harmonics short circuit for undesired harmonics disadvantage – accumulation of harmonics from the nearest networks Active filters: transistor based PWM converters active filter are producing (by means of PWM) higher harmonics (I H ) and reactive components (I J ) of the load current (I Z ) more complicated circuit

Main parts of frequency converters Backplain board Power modules Aluminum body (heat sink) Cooling fan (at the bottom) Cooling from bottom to the top Control circuits, keyboard at front side Aluminum and plastics Control panel, keyboard

Cooling of modules

Typical devices Power modules – integrated semicon. devices cooling – passive/active air-based Inductance-less housing Potential-free copper bases DC link (circuit) – battery of electrolytic capacitors Electrolytic cap. – up to 450/500 V 10 2  F / 500 V, endurance up 600 V outlets – screws or SNAP-IN for soldering into PCB

Unconventional converters (I) for car …. 12/24 VDC for power supply… 12VDC / 230 VAC massive outlets (terminals) heat transfer through whole body compact design very expensive Up/down DC converters:

Unconventional converters (II) Traction converter for trains (CZ type 560) supply voltage 2x 465 V output voltage 730 V output current 630 A (permanently) output current 1200 A (1 min) nominal power 420 kW perman. 465 kW per hour IGCT thyristors operating frequency 600 Hz active cooling 4000 m 3 / hour dimensions 1015 × 930 × 1250 mm weight 460 kg

Unconventional converters (III) Extensible rectifier for underground in Prague installed at line C three-phase bridge, all diodes made as pairs input voltage 660 V AC / 50 Hz output voltage 884 V DC max. input voltage 2000 V output current I DC = 3000 A (permanently) I DC = 4500 A (2 hour) I DC = 9000 A (1 min.)