Skip to main content

अब औरत को लुगाई पढेंगे बच्चे

अब नई शिक्षा नीति के तहत मातृ भाषा में होगी प्राथमिक स्तर तक की पढ़ाई, औरत को लुगाई पढेंगे बच्चे शेखावटी के प्राथमिक स्कूलों के विद्यार्थी अब औरत को लुगाई, आग को बासते और इंसान को मिनख पढ़ते नजर आएंगे। नई शिक्षा नीति के तहत प्राथमिक कक्षाओं में मातृ भाषा में शिक्षा देने की नीति लागू होने से ऐसा होगा। इसके लिए राज्य शैक्षिक अनुसंधान एवं प्रशिक्षण संस्थान ने प्रदेश में संभागवार भाषाई सर्वेक्षण करवाकर स्थानीय भाषा के शब्द कोष तैयार करवाए हैं। शेखावटी के शब्द कोष में शोर को रोला, आदत को बाण, इधर को अठीने, इंतजार को उडीकणों, इकट्ठा को भैळो एवं सांवठो, अध्ययन को पढ़णो, आवास को ठिकाणो, इतना को अतरो, इनकार को नटणों, इसके लिए को इकेपाई एवं अधिक बोलने को लपर-लपर कहा गया है। नई शिक्षा नीति के लिए बच्चों-शिक्षकों की भाषा से शब्दकोष तैयार किया गया है। नई शिक्षा नीति के तहत हुए सर्वेक्षण में प्राथमिक कक्षा के बच्चों की भाषा एवं पढ़ाने वाले शिक्षक की भाषा की जानकारी ली गई थी। इसमें बच्चों के नाम के साथ उनके घर की भाषा, शिक्षक की भाषा, स्कूल का माध्यम, भाषा को समझने एवं बोलने की विद्यार्थियों की क्षम...
Post a Comment

Power diodes | Power electronics

Power diodes

Introduction of power diode

  • Power diode is a two layer, two terminal, p-n semiconductor diode.
  • The two terminal of diode are called anode and cathode.

Characteristic of power diodes

Circuit diagram for characteristic curve of power diode
  • When diode is positive with respect to cathode, diode is said to be forward biased.
  • With increase of Vs from zero value, initially diode current I is zero.
  • From Vs = 0 to cut-in voltage (threshold voltage or truth-on voltage), the forward diode current is very small.
  • After cut in voltage, the forward diode current increases rapidly and the diode is said to conduct.
  • For Si diode, the value of cut-in voltage is 0.7V
  • When diode conduct, there is a forward voltage drop of the order of 0.8 to 1V.
Characteristic curve of power diode
  • When cathode is positive with respect to anode, the diode is said to be reverse biased.
  • In reverse bias condition, a small reverse current, known as leakage current flow in the circuit and this current is of the order of µA or mA.
  • The value of leakage current increases slowly with the increase in reverse voltage up to breakdown or avalanche voltage.
  • At breakdown voltage, the diode is turned on in the reverse direction.
  • The reverse avalanche breakdown of a diode is avoided by operating the diode below specified peak repetitive reverse voltage VRRM.
  • PIV = peak inverse voltage of a diode.
  • The PIV of a diode is the maximum reverse voltage to which a diode may be subjected during its working. It is same as VRRM.

Diode reverse recovery characteristics

  • After the forward diode current decays to zero, the diode continuous to conduct in the reverse direction, due to the presence of stored charges in the two layers.
  • The reverse current flows for a time called reverse recovery time trr.
Reverse recovery characteristic of power diode

Reverse recovery time (trr)

  • Reverse recovery time is defined as the time between the instant forward diode current becomes zero and the instant reverse recovery current decays to 25% of its reverse peak value IRM.
  • trr = ta + tb
  • ta : The time between zero crossing of forward current and peak reverse current IRM. During this time the charge stored in depletion region is removed.
  • tb : It is measured from the instant of IRM to the instant where 0.25 (or 25%) IRM is reached. During this time the charge from the semiconductor layers is removed.
  • During trr, the stored or reverse recovery charge QR must be removed.

Softness factor or S factor

  • The ratio of  tb and ta is known as softness factor or S-factor.
  • The S factor is a measure of the voltage transient that occur during the time, diode recovers.
  • Usually the value of softness factor is found to be unity, which indicates low oscillatory reverse recovery process.
  • If softness factor is small, then diode has large oscillatory over voltages.
  • If S-factor is 1, the diode is called soft-recovery diode.
  • If S-factor is less than 1, the diode is called or fast recovery diode. or snappy recovery diode.
  • If vf is forward voltage drop across diode, and if is forward current
  • vf x if is power loss in diode
  • Fig (c) shows that major power loss in a diode occurs during tb
  • From fig (a), IRM = ta (di/dt)
  • Here IRM = Peak inverse current, and di/dt = Rate of change of reverse current
  • If we assume that reverse recovery characteristic of fig. (a) is triangular, then
  • QR = ½ IRM x trr ⇒ IRM = 2 (QR / trr)
  • ∵  IRM = ta (di/dt)  and  ta = trr 

  • Thus trr (reverse recovery time) and IRM (peak inverse current) depends on QR (storage charge) and di/dt (rate of change of current)
  • Since QR depends on if (forward diode current)
  • So trr and IRM also depends on if.
  • So a power electronics engineer must know the value of IRM, QR, S-factor and PIV to design the circuit in which power diodes are used.
To know more about this topic please click on https://youtu.be/TjZ4fGWCOZI
Labels:

Comments

Post a Comment

Popular posts from this blog

Advantage and Disadvantage of Power Electronics

Advantage and Disadvantage of Power Electronics Advantage of Power electronics Power electronics is used in space shuttle power supplies Since there is very low loss in power electronic devices so its efficiency is very high. Power electronic converter systems are highly reliable. Since there is no moving parts in power electronic systems so it has long life and also its maintenance cost is very less. The power electronic systems has fast dynamic response in comparison to electromechanical converter systems. Since the power electronic system has small size and also it has less weight so they occupy less floor space and hence their installation cost is also less. Now these days power equipments are being mostly used, so power semiconductor devices are being produced on a large scale, resulting in lower cost of converter equipment. Power electronics are used in computer and office equipments. It is used in uninterruptible power supplies. Power...
Post a Comment
Read more

फर्मी डिराक सांख्यिकी | Fermi Dirac statistics in Hindi

फर्मी डिराक सांख्यिकी यह सांख्यिकी फर्मीऑन या फर्मी कणों पर आरोपित की जाती है, अर्थात् वे कण जो अविभेदित हों तथा जिनकी चक्रण क्वांटन संख्या अर्द्ध पूर्णांक हो। कण एक दूसरे से अविभेदित होते हैं। प्रत्येक कोश या उपस्तर में 0 या 1 कण हो सकता है, अर्थात्‌ g i,  >> n i निकाय में कुल कणों की संख्या सदैव नियत रहती है, n = Σn i  = नियत विभिन्न समूहों में स्थित सभी कणों की ऊर्जा का योग अर्थात् निकाय की कुल ऊर्जा सदैव नियत रहती है E = Σn i ε i  = नियत हम n स्वतंत्र समरूप कण, जिनका चक्रण अर्द्ध पूर्णांक है, पर विचार करते हैं। इन कणों को क्वांटम समूहों या स्तरों में इस प्रकार वितरित करना है कि ऊर्जा स्तर             ε 1,  ε 2,  ε 3, ... ε i  अपभ्रष्टता             g 1,  g 2,  g 3, ... g i  कणों की संख्या     n 1,  n 2,  n 3, ... n i  हम एक बक्से पर विचार करते है। इस बक्से में g i  भाग हैं, जिसमें n i  कणों ...
1 comment
Read more

Electric field due to circular loop of charge | Electromagnetics

Electric field due to circular loop of charge Electric field The space around a charged particle in which another charge experience a force is known as electric field. The source of electric field is either a charge or a time varying magnetic field. If the value of electric field does not change with time, then it will be uniform electric field, otherwise it will be non-uniform electric field. Electric field due to circular loop of charge If λ is linear charge density, then the charge on d l dq = λ d l      ⇒     dq = (q / 2πa) d l Electric field at P due to charge dq Special cases When P lies at the centre of the loop i. e., r = 0, then E = 0 When P lies very far from the centre of the loop i. e., r >> a, then E = kq / r 2 In this case circular loop behaves as a point charge. To know more about this topic please click on the link  https://youtu.be/54MIe0Ow43w   or...
Post a Comment
Read more