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Explain the pulse width modulation technique for control of AC output voltage.

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Description : Explain the principle of ON-OFF control and phase control of AC voltage controller with suitable circuit and waveforms.

Answer : The integral cycle control (on-off control) and phase angle control are the two types of AC voltage controller. The principle of ON-OFF control: The on-off control is also called an integral cycle ... control. In phase control, the switch is on for some period of each cycle.  

Description : The clock frequency of an 8085 microprocessor based system is 3 MHz. What should be the minimum pulse width of the INTR signal so that it is recognized successfully? A) 5.6 µs B) 5.7 µs C) 5.8 µs D) 5.9 µs

Answer : The clock frequency of an 8085 microprocessor based system is 3 MHz. What should be the minimum pulse width of the INTR signal so that it is recognized successfully? A) 5.6 µs B) 5.7 µs C) 5.8 µs D) 5.9 µs

Description : Explain series switching control of AC load. Single phase resistance load - Integral half cycle control Phase control - Resistance load

Description : Analyze the effect of supply voltage on performance of LED as regards current, Lumen output, efficacy and life. 

Answer : 1) Effect on Current:- In LED current depends upon supply voltage, if voltage get changes then current also change but this change in current will be control by resistors which are connected in series.  2) ...   4) Effect on Life:- If supply voltage is not stable then life of LED get reduced. 

Description : With the help of N-channel JFET describe the effect of input voltage VGS on output current ID.

Answer : Working of N channel FET: * When a voltage is applied between the drain and source with a DC supply (VDD), the electrons flows from source to drain through narrow channel ... where the channel gets completely blocked and the drain current becomes zero is called pinch- off voltage. 

Description : Define: i) Input Offset Voltage ii) Input offset Current iii) Input Bias Current iv) Output offset voltage

Answer : Definition of parameters of OPAMP is follows:  i) Input Offset Voltage: Input offset voltage is defined as the voltage that must be applied between the two input terminals of an OPAMP to null or ... to ground) and output voltage is obtained non zero such voltage is output offset voltage of opamp.

Description : A linear network has a current input 4cos(ω t + 20º)A and a voltage output 10 cos(ωt +110º) V. Determine the associated impedance.

Answer : Solution

Description : In a battery, the difference between the no-load voltage and the measured voltage output is called ________ A) Internal voltage B) Internal resistance C) External resistance D) All the above

Answer : In a battery, the difference between the no-load voltage and the measured voltage output is called Internal resistance

Description : The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of A) 10 kHz B) 10 Hz C) 5 kHz D) 5 Hz 

Description : Explain how sinusoidal AC voltage is generated by using simple one loop generator.

Answer : An electric current produced by means of electrical machine is known as generator which converts mechanical energy into electrical energy. When conductor cuts the magnetic flux, emf induced in it. (Faraday' ... upon position of armature. The nature of emf is alternating as shown by the waveform. 

Description : Explain the significance of over modulation.

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Answer : The armature voltage control of D.C. motor provides constant torque drive.

Description : What is the difference between a line voltage and low voltage control system?

Description : Why is pulse train gating preferred over pulse gating? Explain with relevant circuit and waveforms, the pulse train gating of SCRs.

Description : Is the power line voltage available in our homes a dc or an ac voltage?

Answer : The power line voltage available in our homes is AC. Mobile dwellings are the most commonly DC-supplied homes and even then they tend to include AC supply for heavier loads.

Description : Draw the waveform of three phase AC supply voltage.

Description : An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be  (1) unaffected (2) decreased (3) increased (4) either decreased or increased depending on the direction of the DC field

Answer : An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be either decreased or increased depending on the direction of the DC field

Description : Explain DC coupled drive circuit with unipolar output.

Answer : DC coupled drive circuit with unipolar output: The figure shows the circuit and waveforms

Description : The ratio of the width to the height of the picture frame is called as A) Rastar B) Aspect Ratio C) Length Ratio D) Efficiency  

Answer : The ratio of the width to the height of the picture frame is called as Aspect Ratio

Description : Explain energy conservation technique “by improving power quality” for induction motor.

Answer : Energy conservation method in induction motor by improving power quality: Electrical energy can be conserved by improving the power quality. It can be achieved by avoiding voltage unbalance, maintaining ... losses can be minimized by using harmonic filter thus reducing the harmonics in the system.

Description : i) State the significance of modulation index in AM transmission. ii) Explain the effect of modulation index on AM wave with waveforms.

Answer : Significance of modulation index in AM transmission  It is used to determine the strength and quality of transmitted signal. If the modulation index is small, then the amount of variation in ... amplitude part of its information is lost in the process of modulation which is undesirable.

Description : Total instantaneous power supplied by a 3-phase ac supply to a balanced R-L load is

Answer : Total instantaneous power supplied by a 3-phase ac supply to a balanced R-L load is constant

Answer : Energy conservation technique in induction motor by minimizing idle and redundant running of motor: 1) Loss of energy as the no load power drawn is approximately about 12% to 16% of rated ... to unnecessary line losses. 4) Reduction in overall system energy efficiency over period of time.

Answer : EPROM EEPROM Flash EPROM Normalize cell size is 1. Normalize cell size is about 1 ... and floating gate, which is insulated by a dielectric material. NAND flash memory and NOR flash memory are the two types of flash memory.

Description : In single pulse modulation of PWM inverters, third harmonic can be eliminated if pulse width is equal to   (a) 30o (b) 60o (c) 120o (d) 150o

Answer : In single pulse modulation of PWM inverters, third harmonic can be eliminated if pulse width is equal to 120o

Description :  A pulse radar has a pulse repetition frequency (PRF) of 3 KHz. If the radar is emitting at 10 GHz, what is the maximum unambiguous range for this radar? A) 5 Km B) 5 m C) 50 Km D) 15 m 

Answer :  A pulse radar has a pulse repetition frequency (PRF) of 3 KHz. If the radar is emitting at 10 GHz, what is the maximum unambiguous range for this radar? A) 5 Km B) 5 m C) 50 Km D) 15 m 

Description : A pulse compression radar transmits an encoded pulse having a frequency chirp from 990 MHz to 1010 MHz centred around 1 GHz. The range resolution capability of this radar is A) 7.5 m B) 7.5 Km C) 75 m D) 750 m 

Answer : A pulse compression radar transmits an encoded pulse having a frequency chirp from 990 MHz to 1010 MHz centred around 1 GHz. The range resolution capability of this radar is 7.5 m

Description : What is the Fourier transform of a Gaussian time pulse? A) Uniform B) Gaussian C) Impulses D) Pulse

Answer : What is the Fourier transform of a Gaussian time pulse? A) Uniform B) Gaussian C) Impulses D) Pulse

Description : A 1ms pulse can be stretched to 1 s pulse by using (A) an astable multivibrator (B) a monostable multivibrator (C) a bistable multivibrator (D) a Schmitt trigger circuit

Answer : A 1ms pulse can be stretched to 1 s pulse by using a monostable multivibrator

Description : State the need of modulation in communication system.

Answer : Need of modulation:- 1. To reduce the height of antenna 2. To avoids mixing of signals 3. To increases the range of communication 4. To make multiplexing of maximum signal is possible 5. To improve the quality of reception

Description : The total power of an AM transmitter having a carrier power of 50 W and the percentage of modulation at 80% is A) 50 W B) 66 W C) 68 W D) 70 W 

Answer : The total power of an AM transmitter having a carrier power of 50 W and the percentage of modulation at 80% is 66 W

Description : What is channel length modulation in MOSFET?

Answer : Shortening of lenght of the inverted channel region with increase in drain bias for large drain biases due to which current increases with drain bias and output resistance decreases is called channel length modulation in MOSFET.

Description : An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms?

Answer : An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms, both resistance and inductance carry equal currents.

Description : What is the point-to-point drawing technique?

Answer : Those who have a hobby of drawing may have a question - what is the essence of such a popular point-to-point technique? A modern fashionable artist has the right to depict reality and his ... , but in different shades, a picture can be obtained with an impressive effect of volume and delicacy.

Description : List the energy conservation technique in induction motor. 

Answer : Following are the list of energy conservation techniques in electrical motors: 1) Reduction in iron losses by using low loss silicon steel core material laminated to thinner dimension. 2) Using bigger length ... at light load. 13) By rewinding in induction motor 14) By motor survey

Description : Cache Mapping Technique

Answer : Cache Mapping Technique:-

Description : Explain full wave bridged rectifier with the help of circuit diagram and input output waveform.

Answer : 1. In positive half cycle (0 to Π): The end A of the secondary winding becomes positive and end B negative. This makes diode D1 and D4 forward biased while diode D2 and D3 are reverse biased. These two diodes will ... D2 and D3 when it is conducting is as follows.  B - D2 - RL - D3 - A 

Description : The largest change of input quantity for which there is no output of instrument is called ______ A) Dead time B) Dead input C) Dead output D) Dead zone

Answer : The largest change of input quantity for which there is no output of instrument is called Dead zone

Description : Explain working of static AC circuit breaker. 

Answer : Static AC Circuit breaker: The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

Description : Explain working of AC circuit breaker using SCR with circuit diagram.

Answer : AC Circuit Breaker:  The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... to non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

Description : State the need for reduction of harmonics in inverters. Enlist the various methods for reduction of harmonics in inverter output.

Description : Speed control of the motor using TRIAC

Answer : Speed control of the motor using TRIAC:  This basic phase triggering circuit uses the triac in series with the motor across an AC sinusoidal supply. The variable resistor, VR1 is used ... meaning that it may not trigger at the exact same point for each positive and negative half cycle.

Description : What is a phase control thyristor?

Answer : PWM means the width of pulse signal can be varied by varying ton & tOFF.

Description : Draw and explain bulk correction method for power factor & control.

Answer : Bulk correction method for power factor & control: i) Here individual starter controls the capacitors located at distribution panel. ii) Centralized compensation is employed in large industrial plants where many ... capacitor units in steps to maintain P.F. more than preset limit (0.95). 

Description : How is a thyristor used to convert AC to DC?

Description : Can transformer convert AC to DC?

Answer : No, Transformer cannot convert AC to DC.

Answer : NO IT ONLY CONVERT FROM AC TO DC BECAUSE DIODE WHICH ARE USED IN IT, ARE UNIDIRECTIONAL.

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