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महाराणा प्रताप ट्रेल सज्जनगढ़ उदयपुर

महाराणा प्रताप ट्रेल सज्जनगढ़ उदयपुर में इको ट्रेल 30 नवम्बर को राजस्थान वन विभाग उदयपुर डिविजन तथा WWF-India उदयपुर डिविजन के सानिध्य में महाराणा प्रताप ट्रेल सज्जनगढ़ उदयपुर में इको ट्रेल की गई, जिसमें WWF-India के स्टेट काॅर्डिनेटर श्रीमान अरूण सोनी तथा वन विभाग कीे ओर से डाॅ. सतीश कुमार शर्मा, सेवानिवृत्त अधिकारी मौजूद थे। मुझे भी इस इको ट्रेल में जाने का सुअवसर प्राप्त हुआ, जो गोरीला व्यू पाॅइंट से बड़ी-लेक व्यू पाॅइंट तक की गई इसमें मुझे विज्ञान की एक नई शाखा के बारे में पता चला, जिसे टट्टी विज्ञान कहा जाता है। सुनने में आपको थोड़ा अजीब लगेगा, मुझे भी सुनकर हैरानी हुई, परन्तु वास्तव में एक ऐसा भी विज्ञान है, जिसके बारे में डाॅ. सतीश शर्मा ने बड़े ही विस्तार पूर्वक बताया कि किस प्रकार वनों में जानवरों की टट्टी देखकर यह पता लगाया जा सकता है कि यहां कौनसा जानवर आया था। जानवरों की टट्टी कितनी पुरानी है, वह गीली है या सूखी है। इसी के आधार पर उस विशेष जंगल में कौन-कौनसे जानवर विचरण करते हैं, उसके बारे में वन विज्ञान के कर्मचारी पता लगा लेते हैं। जानवरों की टट्टी का विश्लेषण करके यह पता लगा...
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MCT | MOS- controlled thyristor | Power electronics

MOS Controlled thyristor (MCT)

  • It is basically a thyristor with two MOSFETs built into the gate structure.
  • One MOSFET is used for turning on the MCT and the other for turning off the device.
  • MCT is a high frequency, high power, low-conducting drop switching device.
  • A practical MCT consists of thousands of these basic cells connected in parallel just like a power MOSFET.
  • This is done to achieve a high current carrying capacity of the device.
Basic structure of MCT
  • The equivalent circuit of MCT consists of one on-FET, one off-FET and two transistors.
  • The on-FET is a p-channel MOSFET and off-FET is an n-channel MOSFET.
  • An arrow towards the gate terminal indicates n-channel MOSFET and the arrow away form the gate terminal is the p-channel MOSFET.
  • The two transistor in the equivalent circuit represents that there is regenerative feedback in the MCT just same as in an ordinary thyristor.
(a) Equivalent circuit of MCT and (b) Circuit symbol of MCT

Turn-on process

  • An MCT can be turned on by applying a negative voltage pulse at the gate with respect to anode.
  • By getting this negative voltage pulse, on-FET gets turned-on and the off-FET is off.
  • During this time current begins to flow from anode A, through on-FET and then as the base current (iB) and emitter current (iE) of npn transistor and then to cathode C.
  • It turns on transistor and therefore collector current (iC) begins to flow in npn transistor.
  • Since off-FET is off, so this iC of npn transistor acts as the iB of pnp transistor, and hence pnp transistor is also turned on.
  • When both the transistors are on, the regenerative action of the connection scheme takes place, and the MCT is turned on.

Turn-off process

  • For turning-off the MCT, off-FET is energized by positive voltage pulse at the gate with respect to anode.
  • So this FET is turned on, and on-FET is tuned off.
  • After off-FET is tuned on, either base terminals of pnp transistor are short circuited by it.
  • So the anode current begins to flow through off-FET and therefore iB of pnp begins to decrease.
  • So iC of pnp transistor that forms the iB also begins to decrease.
  • In this way iB of pnp and npn transistors divide storage charge in their n and p bases respectively, begins to decay.
  • This regenerative action turns off the MCT.

Advantages of MCT

  • MCT has low forward conduction drop.
  • The turn-on and turn-off time of MCT is very fast.
  • The switching loss of MCT is very low.
  • The gate input impedance of MCT is very high.
To know about this lecture in more detail please visit on https://youtu.be/KtNQJ3Sueo0
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