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Power electronics switching circuit

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  • Welcome back friendsNow lets start with power electronics switchingHow to switch AC and Power Load by using Microcontroller?This can be done in two waysElectromagnetic relay switchingStatic SwitchingDue to long life efficient silent and reliable operation static switching is preferred over electromagnetic RelayHere my discussion is concerned only with static switching i.e Power electronics switchingAs I had said earlier Power electronics the most dominating technology of this centuryA link between computer and Real life applications(i.e Electrical system)Widely used in almost all the electrical systems of todayEither it be POWER TRANSMISSION – FACTSOr MOTOR CONTROL-ELECTRIC DRIVE today even inside Advanced electric machine power electronic circuit are used for better commutation and efficient operation
  • Let’s start to build switching circuit

Transcript

  • 1. Module for Static Control of 220V AC Devices by Arduino/IR remote
  • 2. Selection of Power switching Device Isolation between Arduino and Power circuit Circuit & Load connection
  • 3. Selection of Power switching Device There are lots of Power semiconductor switches 1. Diode(Uncontrolled Turn ON/OFF) 2. Thyristors(Controlled turn ON and Uncontrolled Turn OFF ) • SCR • TRIAC • GTO 3. Transistors(Controlled turn ON and controlled Turn OFF ) • Power BJT • Power MOSFET • IGBT Desired Characterstics • Pulse Gate • Controlled Turn ON • Bipolar voltage • Low cost (low switching frequency)
  • 4. Selection of Power switching Device TRIAC is Best suited • Low Cost • Bipolar voltage • Isolator Driver is easily available • Zero crossing Detection can be used to Turn ON • Voltage control is possible for Dimming of Bulb/Speed control of Fan
  • 5. Selection of Power switching Device Basic Operation of TRIAC TRIACs are like 2 antiparallel SCRs with a common gate They are thus able to switch both sides of an AC sine wave A TRIAC switch controls the current through a load Because it can be controlled to trigger at different voltage points on the sine wave it can be used to effectively control the RMS power delivered to the load rather just crude on / off.
  • 6. Selection of Power switching Device Basic Operation of TRIAC It's like a switch that can turn on and off at different times on the sine wave. Is this only what we need to do? Of course not
  • 7. Selection of Power switching Device What we want to do with TRIAC What is basically difference between last waveform and this one? We want to Switch ON and OFF AC load To Generate Vg we Use MOC 3041 in our case
  • 8. • These devices provide sufficient gate trigger current for high current, high voltage Triac, while providing a guaranteed 7.5 kV dielectric withstand voltage between the power line and the control circuitry • An integrated, zero-crossing switch on the detector chip eliminates current surges and the resulting electromagnetic interference (EMI) and reliability problems for many applications. Isolation between Arduino and Power circuit WHY?? The high transient immunity of 5000 V/μs, combined with the features of low coupling capacitance, high isolation resistance and up to 800 volt specified V DRM ratings qualify this Triac driver family as the ideal link between sensitive control circuitry and the ac power system environment. The zero-cross family of optically isolated Triac drivers is an inexpensive, simple and effective solution for interface applications between low current dc control circuits such as logic gates and microprocessors and ac power loads
  • 9. • OptoIsolators are Used in case of TRIAC • MOC 304_ series I.C. are used Isolation between Arduino and Power circuit HOW??
  • 10. Isolation between Arduino and Power circuit How does Zero crossing optically isolated Triac driver works? Gates of the individual SCRs are connected to high speed zero crossing detection circuits. This insures that with a continuous forward current through the LED, the detector will not switch to the conducting state until the applied ac voltage passes through a point near zero The detector chip is a complex monolithic IC which contains two infrared sensitive, inverse parallel, high voltage SCRs which function as a light sensitive Triac .
  • 11. • A forward current flow through the LED generates infrared radiation which triggers the detector. • zero crossing detection circuit insures that the detector will not switch to the conducting state until the applied ac voltage passes through a point near zero Isolation between Arduino and Power circuit
  • 12. Isolation between Arduino and Power circuit Electrical Characteristics The detector/Triac may be triggered "on“ in following ways • This LED trigger current (IFT) • Exceeding the forward blocking voltage between the two main terminals (MT1 and MT2) • Voltage ramps (transients, noise, etc.) which are common in ac power lines may trigger the detector accidentally if they exceed the static dV/dt rating Accidental triggering of the main Triac is a more likely occurrence thus a form of suppression network commonly called a "snubber" must be used to prevent false "turn on" of the main Triac
  • 13. Isolation between Arduino and Power circuit BASIC SWITCHING CIRCUIT With TRIAC , TRIAC DRIVER & LOAD The gate resistor RG is only necessary when the internal gate impedance of the Triac or SCR is very high .These devices display very poor noise immunity and thermal stability without RG Resistor R (in combination with R-C snubber networks) prevents possible destruction of the Triac driver in applications where the load is highly inductive. LIMITATION Use of a gate resistor combined with the current limiting resistor R can result in an unintended delay or phase shift between the zero-cross point and the time the power Triac triggers.
  • 14. BASIC SWITCHING CIRCUIT With TRIAC , TRIAC DRIVER & LOAD Load connection
  • 15. Calculation of Rs and Cs If R, L and C are chosen to resonate, the voltage waveform on dV/dt due to damped quarter- cycle of oscillation will look like. Load connection
  • 16. Calculation of Rs and Cs Load connection
  • 17. Load connection
  • 18. DEMO