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How do you test an SCR?

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Description : How do you test a capacitor with a multimeter?

Description : How do you test a triac?

Description : How do we test a diode?

Description : In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in (A) voltage notching (B) harmonic distortion (C) voltage sag (D) voltage swell

Answer : In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in voltage notching

Description : How GTO is advantages over SCR

Answer : i) It is turned-off by negative gate pulse. ii) No commutation circuit required, reducing the cost, size, weight and volume of the circuit. iii) As commutation choke is not used, the associated acoustic ... turn off time permits high switching frequency. v) It has higher di/dt rating at turn-off. 

Description : An inductor is connected in series with SCR to protect it from A) Excessive high voltage B) Excessive high dv/dt C) Excessive high di/dt D) Excessive large forward current 

Answer : An inductor is connected in series with SCR to protect it from Excessive high di/dt

Description : An SCR without any external connections is considered as (A) two diodes in series (B) three diodes in series (C) two n-p-n transistors in series (D) two p-n-p transistors in series

Answer : An SCR without any external connections is considered as three diodes in series

Description : If a 5-bus test system contains 6 transmission lines and one transformer, how many non-zero elements are there in the system Y-bus ? (A) 25 (B) 12 (C) 11 (D) 19

Answer : If a 5-bus test system contains 6 transmission lines and one transformer, 19 non-zero elements are there in the system Y-bus.

Description : drive the expression for the  (1)current that commutates the scr, (2)the peak current, (3) conduction time?  in class B,C,D and E.

Description : Purpose of Selective Catalytic Reduction (SCR)

Answer : Purpose of Selective Catalytic Reduction (SCR) : 1. It reduces Nox 75% to 90% 2. Converts it in to molecular nitrogen and water vapor 3. It reduces HC emission up to 80% 4. It reduces PM emission 20 to 25%.

Description : Explain triggering of SCR using opto-coupler. State its advantages. 

Answer : Triggering of SCR using opto-coupler:  A simple opto-coupler based triggering circuit for SCR is shown in the figure. An optocoupler or opto-isolator is a combination of light source ... is small size and light weight device. iii)Interfacing with logic circuits is easily possible.

Description : Draw the circuit diagram of battery charger using SCR and explain it’s working.

Answer : Battery charger circuit using SCR: The figure shows the battery charger circuit using SCR. A 12V discharged battery is connected in the circuit and switch SW is closed. The singlephase 230V ... not fired. In this way, after full charging, further charging is automatically stopped.

Description : Explain the thermal triggering method of SCR. Enlist different triggering methods of SCR.

Answer : Types of Triggering: 1) Forward voltage triggering 2) Thermal triggering (Temperature triggering) 3) Radiation triggering (Light triggering) 4) dv/dt triggering 5) Gate triggering ... generated leakage current increases. This current gets multiplied internally and thyristor is turned on. 

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 : Temperature controller using SCR

Answer : Temperature controller using SCR The temperature control circuit is used to regulate the temperature. Figure shows the temperature control circuit using thermostat as temperature detector and SCR as ... half-cycle and heater gets connected to source to produce heat and raise the temperature.

Description : Compare SCR and TRIAC

Answer : SCR TRIAC It is an unidirectional device. It is a bidirectional device. It is turned-on by only positive gate current. It can be turned-on by either ... applications including lamp dimmer, heating control, zero voltage switched AC relay, small AC motor control etc.

Description : Describe triggering of SCR using UJT relaxation oscillator. 

Answer : Triggering of SCR using UJT relaxation oscillator: 

Description : Draw a neat labelling V-I characteristics of SCR and explain the region

Answer : (i) Latching current: It is the minimum anode current required to maintain the SCR in the conduction state just after turn-on and the gate signal has been removed.  (ii) Holding current: It is the minimum anode current required to hold the conducting SCR in the ON state. 

Description : Draw construction of SCR using two transistor model. Explain its operation.

Answer : Two Transistor Model of SCR or Thyristor

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 : SCR is more utilized as compared to Triac because it is

Answer : SCR is more utilized as compared to Triac because it is available with higher ratings

Description : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) ... proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

Answer : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ directly proportional to α and inversely proportional to Φ

Description : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is (A) 4.5 V (B) 6.75 V (C) 9 V (D) 13.5 V

Answer : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is 9 V

Description : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is (A) sinusoidal current (B) constant dc current (C) continuous rectangular pulses (D) alternating rectangular pulses

Answer : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is alternating rectangular pulses

Description : Why SCR is called as thyristor?

Description : Is a SCR a thyristor?

Answer : Yes, SCR is a thyristor. Thyristor is the family and SCR is the member of that family but SCR is universally known as thyristor.

Answer : Yes, SCR is a unidirectional switch.

Answer : SCR turned off when the anode current falls below holding current.

Description : What is holding current and latching current in SCR? Draw the gate characteristics of an SCR and explain the characteristics. What are the different signals which can be used for turning on SCR by gate control? compare them.

Answer : (i) Holding Current: Holding current is defined as the minimum anode current required to maintain conducting SCR in the on-state.  (ii) Latching Current: Latching current is defined as the ... the on-state immediately after the SCR has been turned on and the gate signal has been removed.

Description : What is the use of SCR?

Answer : SCR are use in lamp dimming, power regulators, motor control, rectifications of high power AC, control of welding machines and also use as switch these are some uses of silicon controlled rectifier.

Description : Slip test is performed to determine :  (A) Slip in an induction motor  (B) Xd and Xq in a salient pole alternator  (C) Synchronous impedance in an alternator  (D) Positive and negative sequence impedances of an alternator

Answer : Slip test is performed to determine :  Xd and Xq in a salient pole alternator 

Description : An open-circuit test on a transformer is conducted primarily to measure?

Answer : The open-circuit test in a transformer is used to measure

Description : What is an insulation resistance test?

Description : Earth General Knowledge Test

Answer : Earth General Knowledge Test Its a common perception that the earth began billions of years ago as a huge ball of swirling dust and gases. Lightning strikes about 6,000 times per minute on earth. and ... Oxygen is the most abundant element in the Earth's crust, waters, and atmosphere (about 49.5%)

Description : Animal General Knowledge Test

Answer : Animal General Knowledge Test The Earth has over 12,00,000 species of animals, 3,00,000 species of plants & 1,00,000 other species. All polar bears are left handed A cow gives nearly 200, ... animal by tearing off with its dagger like claw. The largest frog in the world is called Goliath frog.

Description : Polarity Test of Transformer

Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Description : Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.

Description : With the help of neat diagram, describe the procedure to carry out phasing out test on a 3 phase transformer. Also state the purpose of conducting this test on 3 phase transformer.

Answer : i) This test is carried out on 3-ph transformer to identify primary & secondary winding belonging to the same phase. ii) As shown in fig above all primary & secondary phases ... of this test is to check the respective phases of primary & secondary windings in 3-ph transformer

Description : Explain the open delta (delta-delta) test on transformer.

Description : DC motor brake test numerical

Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Description : Brake test on DC series motor

Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Description : Explain the need and steps to conduct the reduced voltage running up test on the three phase induction motor.

Description : Why phasing out and polarity test is carried out on three phase transformer?

Answer : The phasing out test is carried out to identify the windings (primary and secondary) of corresponding phase of the three phase transformer. The polarity test is carried out to identify the ... identical polarity of the primary and secondary windings of each phase of the three phase transformer.

Description : What is test bench? Write its applications

Answer : Test Bench: A test bench is used to verify the functionality of the design. We need to stimulate our designs in order to test their functionality. Stimulus in a real system is from an ... the entity under test and to collect output responses. 6. To compare output responses with expected values.

Answer : Murray loop test can be used for location of both the ground fault and the short-circuit fault.

Answer : Hopkinson's test on D.C. machines is conducted at full-load.

Answer : The duration of sudden short-circuit test on a synchronous motor is usually about one second.

Description : During open circuit test of a transformer?

Answer : During open circuit test of a transformer primary is supplied rated voltage.

Answer : Short circuit test on transformers is conducted to determine copper losses.

Description : A no-load test is performed on a transformer to determine?

Answer : A no-load test is performed on a transformer to determine magnetizing current and loss.

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