For speed control of ac drive, the preferred method using thyristors is 

A) Phase control B) Integral cycle control C) Single pulse PWM control D) Sinusoidal PWM control

1 Answer

Answer :

For speed control of ac drive, the preferred method using thyristors is Sinusoidal PWM control

Related questions

Description : In an adjustable speed ac drive which quantity gets reduced above rated speed ? (A) developed torque (B) stator frequency (C) reduced starting torque (D) stator current

Last Answer : In an adjustable speed ac drive which quantity gets reduced above rated speed ? (A) developed torque (B) stator frequency (C) reduced starting torque (D) stator current

Description : Why thyristors are not preferred for inverters?

Last Answer : Thyristors require extra commutation circuits for turn off which resulting Increased complexity of the circuit. For these reasons thyristors are not preferred for inverters.

Description : RC triggering is preferred over resistance triggering because (A) it provides triggering at a precise instant (B) it gives a longer duration gate pulse (C) it enables triggering at a larger value of firing angle (D) it protects the SCR against high dv/dt

Last Answer : a

Last Answer : For constant torque drive armature voltage control speed control method is preferred.

Description : In v/f control method,   (a) The maximum torque decreases (b) The motor speed increases (c) The maximum torque is constant (d) The maximum torque increases

Last Answer : In v/f control method, The maximum torque is constant 

Description : The direction of rotation of an inverter fed 3-phase ac motor is reversed by (A) a mechanical reversing switch (B) reversing the input dc link voltage (C) operating the inverter as a rectifier (D) changing the sequence of switching

Last Answer : The direction of rotation of an inverter fed 3-phase ac motor is reversed by changing the sequence of switching

Description : In static Kramer drive, motor turns ratio is 0.6, the firing angle is 120o. The motor slip is   (a) 0.633 (b) 0.533 (c) 0.833 (d) 0.733 

Last Answer : In static Kramer drive, motor turns ratio is 0.6, the firing angle is 120o. The motor slip is 0.833

Description : Scherbius Drive System

Last Answer : Scherbius Drive System

Description : Kramer Drive System

Last Answer : Kramer Drive System Kramer drive is a rotor side speed control drive of induction motor. Slip is the difference between synchronous speed and rotor speed. It is the ... and DC motor. The static Kramer drive is costlier because of the cost of DC motor.

Description : In electric traction for a trapezoidal speed-time curve, the time period is (A) free running speed period = constant speed period (B) free running period = coasting period (C) free running period + coasting period = constant speed period (D) average speed period = scheduled speed period

Last Answer : In electric traction for a trapezoidal speed-time curve, the time period is free running period + coasting period = constant speed period

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

Last 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 : Why diodes should be connected in antiparallel with the thyristors in inverter circuits?

Last Answer : For RL loads, load current will not be in phase with load voltage and the diodes connected in antiparallel will allow the current to flow when the main thyristors are turned off. These diodes are called feedback diodes.

Description : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO 

Last Answer : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO 

Description : Which phenomenon is present in thyristors but absent in BJT, MOSFET and IGBT ? (A) forward conduction (B) latching (C) forward blocking (D) reverse breakdown

Last Answer : Which phenomenon is present in thyristors but absent in BJT, MOSFET and IGBT ? (A) forward conduction (B) latching (C) forward blocking (D) reverse breakdown

Description : Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method due to:  (1) Better speed regulation (2) Less loss in external resistance (3) Simplicity in control circuit (4) Reduced cost of controller

Last Answer : Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method due to: Better speed regulation.

Description : In a three phase controlled bridge rectifier with an increase of overlap angles the output dc voltage

Last Answer : In a three phase controlled bridge rectifier with an increase of overlap angles the output dc voltage decreases

Description : In a thyistorised converter a free wheeling diode is used to  A) Add to the conduction current ofthe thyristor B) Oppose the thyristor conduction C) Conduct current during the off period of the thyristor D) Protect the thyristor by providing a shunt path

Last Answer : In a thyistorised converter a free wheeling diode is used to Conduct current during the off period of the thyristor

Description : In d.c. choppers, for periodic time T, the output voltage can be controlled by frequency modulation by varying

Last Answer : In d.c. choppers, for periodic time T, the output voltage can be controlled by frequency modulation by varying T, keeping ton constant

Description : A step-down chopper, fed from a 120 volt DC source, operates a DC motor whose armature e.m.f. and armature resistance are 100 volt and 0.5Ω respectively. With the magnitude control ratio 0.6, the quadrant of operation DC motor is  (a) First (b) Second (c) Third (d) Fourth

Last Answer : A step-down chopper, fed from a 120 volt DC source, operates a DC motor whose armature e.m.f. and armature resistance are 100 volt and 0.5Ω respectively. With the magnitude control ratio 0.6, the quadrant of operation DC motor is First

Description : The ripple factor of a bridge rectifier is  1.0.48 2.0.812 3. 1.11 4. 1.21 

Last Answer : The ripple factor of a bridge rectifier is 0.48

Description : A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% ... to the DC supply is  (a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW

Last Answer : 48

Description : Specific energy consumption of an electric train is the ratio between (A) Specific energy output at driving wheels and efficiency of the traction motor (B) Specific energy output at driving wheels ... (D) Specific energy output at driving wheels and efficiency of the (motor + transmission gear)

Last Answer : Specific energy consumption of an electric train is the ratio between Specific energy output at driving wheels and efficiency of the (motor + transmission gear)

Description : A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is (A) 9997 Ω (B) 10000 Ω (C) 997 Ω (D) 10003 Ω

Last Answer : A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is 9997 Ω

Description : Slip-Energy Recovery (SER) scheme for three phase Induction Motor

Last Answer : Slip-Energy Recovery (SER) scheme for three phase Induction Motor

Description : Chopper controlled DC motor

Last Answer : Chopper controlled DC motor

Description : Why AC systems are preferred over DC systems?

Last Answer : Due to following reasons, AC systems are preferred over DC systems: a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution. b. Plant cost for AC ... the sine wave current will naturally tend to zero at some point making the current easier to interrupt.

Description : HVDC transmission is preferred to EHV AC because  (a) HVDC terminal equipments are inexpensive  (b) VAR compensation is not required in HVDC systems  (c) System stability can be improved  (d) Harmonic problem is avoided 

Last Answer : C- system stability can be improved

Description : The most practical method of controlling the RPM of a step-speed AC motor is to _____________. A. change input voltage B. vary the number of poles C. vary power factor D. change the number of brushes

Last Answer : Answer: B

Description : The standard method of controlling the output voltage of a 440 volt, 60 Hz, AC generator is accomplished by adjusting the ____________. A. prime mover speed droop B. number of poles C. alternator field excitation D. load on the alternator

Last Answer : Answer: C

Description : The most practical way to control the voltage output of an AC generator is to vary the _____________. A. number of windings B. speed of the rotating field C. strength of the rotating magnetic field D. power factor of the load

Last Answer : Answer: C

Description : Automatic voltage regulators provided on switchboards function to _____________. A. regulate the AC load on the generator B. protect the switchboard from high voltage C. govern prime mover speed to control voltage D. vary the field excitation to the generators

Last Answer : Answer: D

Description : The function of the autotransformers used with the starters of large AC motors is to provide _____________. A. increased voltage for starting B. increased torque for starting C. reduced voltage for starting D. speed control

Last Answer : Answer: C

Description : A large dc motor is required to control the speed of the blower from a 3 -phase ac source. The suitable ac to dc converter is, 3 -phase (a) Fully controlled bridge converter ( ... bridge converter with freewheeling diode (c) Half controlled bridge converter (d) Converter pair in sequence control

Last Answer : a fullu control

Description : While paralleling two (2) AC generators using synchronizing lamps only, both lamps will go dark when the generators are ____________. A. running at the same speed B. grounded C. of the same polarity D. in phase

Last Answer : Answer: D

Description : Do you have a preferred method of preparing kale chips?

Last Answer : When I did them they were very dark green, almost the same color of seaweed snacks. I rinsed then, patted them dry and toasted them in the oven. To do that I laid them in a single layer, on a sheet ... to taste with salt. I usually put a clove of garlic or two so I have some roasted garlic as well.

Description : What's your preferred method for making iced tea?

Last Answer : Sun tea is my favorite. You just put a bunch of teabags in a tightly sealed jar of water and leave it in direct sunlight for a few hours. Best tasting iced tea in the world.

Description : Which method of purchase is preferred for micro-purchases?

Last Answer : An offeror's experience as an evaluation factor consistsprimarily of:

Description : Which of these is a preferred method of death and destruction by terrorists?

Last Answer : IEDs

Description : Dilution method of disposing of sewage, is not preferred to A. When sewage is fresh B. When diluting water has high dissolved oxygen content C. When diluting water is used for water supply near the point of sewage disposed D. When the diluting water is having flow currents

Last Answer : ANS: C

Description : For locating a distant object visible from two transit stations, the method usually preferred to, is  (A) Angles and distances from transit stations  (B) Angles from two transit stations  ... from two transit stations  (D) Angle from one transit station and distance from the other 

Last Answer : (B) Angles from two transit stations 

Description : The method generally preferred to for contouring an undulating area, is (A) Chain surveying (B) Plane table surveying (C) Tacheometrical surveying (D) Compass surveying

Last Answer : (C) Tacheometrical surveying

Description : What is the preferred method for stripping wire?

Last Answer : By use of a wire-stripping tool

Description : What is the preferred method of repairing cracked runs on boards?

Last Answer : Clinched staple.

Description : What is the most preferred method of troubleshooting?

Last Answer : Testing components by comparison

Description : ………………… is preferred method for enforcing data integrity A) Constraints B) Stored Procedure C) Triggers D) Cursors

Last Answer : A) Constraints

Description : ……………. is a preferred method for enforcing data integrity A) Constraints B) Stored procedure C) Triggers D) Cursors

Last Answer : A) Constraints

Description : Delta Air Lines wishes to purchase five new aeroplanes. Management seeks information from several aircraft manufacturers, screens the offers, and discusses price and terms of sale with the preferred company until a ... method of pricing is: A)administered. B)sealed bid. C)open bid. D)negotiated.

Last Answer : D)negotiated.

Description : For enhancing the power transmission in along EHV transmission line, the most preferred method is to connect a  (A) Series inductive compensator in the line (B) Shunt inductive compensator at the ... (C) Series capacitive compensator in the line (D) Shunt capacitive compensator at the sending end

Last Answer : For enhancing the power transmission in along EHV transmission line, the most preferred method is to connect a Series capacitive compensator in the line

Description : Which light emitter is preferred for high-speed data in a fiber-optic system? ∙ A. incandescent ∙ B. LED ∙ C. neon ∙ D. laser

Last Answer : D. laser