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 ...

Power Electronic Systems The output of a power electronic converter circuit depends on the requirement of the load. Example If the load is a dc motor, then the output of converter must be an adjustable direct voltage. If the load is a 3-phase induction motor, then the converter may have adjustable voltage and frequency at its output terminals. In power electronic systems, the feedback component measures a parameter of the load and also compare it with the command. For example it measures the speed in case of a rotating machine. To know about this lecture in more detail please visit on https://youtu.be/Yfwi8uHUIxY

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...

Principle of phase control The simplest form of controlled rectifier circuit consists of a single thyristor feeding dc power to a resistive load R. An SCR can conduct only when anode voltage is positive and a gating signal is applied. It is found that a thyristor blocks the flow of load current until it is triggered. Since by varying the firing angle, the phase relationship between the start of the load current and supply can be controlled, hence the term phase control is used for such a method of controlling the load current. Since this circuit produces only one pulse of load current during one cycle of source voltage, so it is single phase half wave circuit. To know about the principle of phase control by using a simplest form of controlled rectifier circuit which includes a thyristor, a resistor and an a.c. source please see our latest video on https://youtu.be/5qwOYhAWHsU The wave pattern of gate current, load voltage, load current an...

Power Devices Introduction of power device Power semiconductor diodes are similar to low power pn-junction diodes. Power transistors are identical with npn or pnp signal transistors. Power diodes are constructed with n - layer, this n - layer is called drift region , which exists between p + layer and n + layer. The p + and the n + layers are known as anode, and cathode (substrate) respectively. The n - layer is used to support a large blocking voltage. This n - layer is not present in low power diodes or signal diodes. Note:   The low power diodes and transistors are also known as signal diodes and signal transistors respectively. Difference between Power semiconductor and Signal semiconductor Power semiconductor diode and transistor Signal semiconductor diode and transistor The voltage, current and power ratings of these devices are high. The voltage, current and power ratings are these devices are ...

Types of Power Diodes The power diodes are mainly classified into following three categories: General purpose diode The value of t rr for these diodes are vey high, and it is about 25µs. The current rating for general purpose diode is from 1A to several thousand amperes. The voltage rating of general purpose diodes are from 50V to 5kV. Uses The general purpose diodes are used in battery charger. These diodes are also used in electric traction. The general purpose diodes are also used in electroplating. In welding works, the general purpose diodes are very useful. These diodes are used in uninterruptible power supply (UPS) too. Fast recovery diode The value of t rr  of fast recovery diode is low and it about 5µs or less. Its current rating is from 1A to several thousand amperes. The voltage rating of fast recovery diodes are from 50V to 3kV. If we require the voltage rating of fast recovery diode below 40...

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 V s from zero value, initially diode current I is zero. From V s = 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 curre...

Introduction of power electronics Power electronics belongs partly to power engineers and partly to electronics engineers. It means it is the combination of power engineering and electronics engineering. Power engineering is mainly concerned with generation, transmission, distribution and utilization of electric energy at high efficiency. The simple engineering is guided by distortion-less production, transmission and reception of data and signals of very low power level of the order of a few watts, or milliwatts without much consideration of the efficiency. Power electronics is also known as industrial electronics. The apparatus associated with power engineering is based mainly on electromagnetic principles, whereas in electronics engineering they are based on physical phenomenon in vacuum, gases/vapours and semiconductors. This subject concerns the application of electronic-principles into situations that are rated at power levels rather than signal levels. It may a...