A single-phase half-controlled rectifier is driving a separately excited dc motor. The dc motor has a back emf constant of 0.5 V/rpm. The armature current is 5 A without any ripple. The armature resistance is 2 Ohm. The converter is working from a 230 V, single-phase ac source with a firing angle of 30o . Under this operating condition, the speed of the motor will be 

(A) 339 rpm (B) 359 rpm (C) 366 rpm (D) 386 rpm

1 Answer

Answer :

359

Related questions

Description : A separately excited dc motor is required to be controlled, from a 3-phase supply, for its operation in the first quadrant only. The most preferred converter would be  (a) 3-phase fully controlled ... converter with free wheel diode (c) 3-phase dual converter (d) 3-phase half wave converter 

Last Answer : A

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 : A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor :  (A) can be operated in first quadrant (B) ... in first & second quadrants (C) can be operated in first & fourth quadrants (D) cannot be operated

Last Answer : A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor : can be operated in first & fourth quadrants

Description : A separately excited d.c. motor fed from single phase full converter with firing angle 60° runs at 1000 r.p.m. If motor is connected to single phase semiconverter with the same firing angle of 60°, it would run at (a) 2000 rpm (b) 1850 rpm (c) 1500 rpm (d) 1000 rpm 

Last Answer : Ans =1500

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 : Separately Excited DC motor

Last Answer : Separately Excited DC motor

Description : A single phase, half-wave, controlled rectifier has 400 sin (314 t) as the input voltage and R as the load. For a firing angle of 60° for the SCR, the average output voltage is   (a) 240/π (b) 400/π (c) 300/π (d) 200/π 

Last Answer : C

Description : The ripple voltage in the output of a single phase half wave rectifier with 10 V rectified dc voltage with resistive load and without filter will be • 12.1 volt • 1.21 volt • 0.482 volt • 4.82 volt

Last Answer : The ripple voltage in the output of a single phase half wave rectifier with 10 V rectified dc voltage with resistive load and without filter will be 12.1 volt

Description : Which of the following statements represents an application of a silicon controlled rectifier? A. To provide DC power for a main propulsion motor. B. For use as a voltage reference diode. C. For sensing flame in an automated burner. D. To eliminate power supply hum.

Last Answer : Answer: A

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 : What is the difference between self-excited and separately excited DC generator? 

Last Answer : Self-excited generator: In a self-excited generator the field winding is excited by an external DC source like a battery etc. Separately excited generator: In a separately excited generator the field poles ... is again fed to the field winding and goes on till the generator builds up voltage. 

Description : The supply both to field and armature circuits are disconnected simultaneously in a separately excited dc motor and it comes to a standstill in 5 sec. If the armature circuit of this motor is disconnected from supply with field ... rest in (1) 5 sec (2) 7 sec (3) 4 sec (4) A very long time  

Last Answer : 5 sec only.standstill time doesn't depend upon field excitation

Description : As shown in the illustration, the generator field is excited with DC current provided by ____________. EL-0016 A. conductors '1', '2' and '3' B. inductor 'L1' C. rectifier 'CR1' D. winding 'S-2'

Last Answer : Answer: C

Description : On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush ... B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation

Last Answer : Answer: B

Description : what is separately excited motor ?

Last Answer : the field winding have different source power supply and armature have different power supply source

Description : Single-phase mid-point controlled rectifier with RL load

Last Answer : Single-phase mid-point controlled rectifier with RL load : The circuit configuration of single-phase midpoint controlled rectifier is shown in the figure. During positive half-cycle of ... some part of next positive half-cycle of voltage with reversed polarity can appear across load.

Description : Single-phase Midpoint controlled rectifier with Resistive load

Last Answer : Single-phase Midpoint controlled rectifier with Resistive load:  1) During positive half cycle of AC supply, a is positive with respect to b , this makes T1 forward biased and T2 is reverse ... voltage reverses the polarity and T2 is turned off. The operation is as shown in waveforms.

Description : When the firing angle a of a single-phase, fully controlled rectifier feeding constant direct current into a load is 30°, the displacement power factor of the rectifier is

Last Answer : When the firing angle a of a single-phase, fully controlled rectifier feeding constant direct current into a load is 30°, the displacement power factor of the rectifier is √3/2

Description : A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 ... three phase source, the phase sequence being consistent with the direction of rotation. In steady state

Last Answer : A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 1pm. ... rotation. In steady state DC machine acts as a motor and the induction machine acts as a generator  

Description : Why back emf used for a dc motor? highlight its significance.

Last Answer : The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the ... speed of rotation of the armature conductors. In starting, the value of back emf is zero.

Last Answer : Back emf: When the armature of DC motor rotates under the fixed magnetic field and cuts it, by Faraday's law an emf is induced in them. The induced emf acts in opposite direction to the ... the flow of armature current i.e. it automatically changes the armature current to meet load requirements. 

Description : A silicon controlled rectifier (SCR) is a solid state device used to change ________________. A. DC to AC and control relatively low load current B. AC to DC and control relatively high load ... to AC and control relatively high load current D. AC to DC and control relatively low load current

Last Answer : Answer: B

Description : The correct term for the illustrated circuit is a ________. EL-0063 A. single phase half wave high power rectifier B. three phase half wave rectifier C. three phase full wave rectifier D. a single phase full wave rectifier

Last Answer : Answer: C

Description : A single-phase induction motor with only the main winding excited would exhibit the following response at synchronous speed  (A) Rotor current is zero (B) Rotor current is non-zero and is ... and backward rotating fields are equal (D) Forward rotating field is more than the backward rotating field

Last Answer : A single-phase induction motor with only the main winding excited would exhibit the following response at synchronous speed  (A) Rotor current is zero (B) Rotor current is non-zero and is ... backward rotating fields are equal (D) Forward rotating field is more than the backward rotating field

Description : A three-phase, 440 V, 50 Hz ac mains fed thyristor bridge is feeding a 440 V dc, 15 kW, 1500 rpm separately excited dc motor with a ripple free continuous current in the dc link under all operating conditions, Neglecting the ... at half the rated speed is  (A) 0.354 (B) 0.372 (C) 0.90 (D) 0.955

Last Answer : A three-phase, 440 V, 50 Hz ac mains fed thyristor bridge is feeding a 440 V dc, 15 kW, 1500 rpm separately excited dc motor with a ripple free continuous current in the dc link under all operating conditions, Neglecting the losses, the power factor of the ac mains at half the rated speed is 0.354

Description : A single-phase fully controlled thyristor bridge ac-dc converter is operating at a firing angle of 25o and an overlap angle of 10o with constant dc output current of 20 A. The fundamental power factor (displacement factor) at input ac mains is  (A) 0.78 (B) 0.827 (C) 0.866 (D) 0.9

Last Answer : A single-phase fully controlled thyristor bridge ac-dc converter is operating at a firing angle of 25o and an overlap angle of 10o with constant dc output current of 20 A. The fundamental power factor (displacement factor) at input ac mains is 0.78

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

Last 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 : What is meant by phase controlled rectifier?

Last Answer : It converts fixed ac voltage into variable dc voltage.

Description : What is delay angle or what is firing angle of phase controlled rectifier?

Last Answer : The delay angle is the angle at which thyristors are triggered after zero crossing. After zero crossing of supply voltage, one pair of thyristors is forward biased. After delay angle(α) these SCRs are triggered.

Description : The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Last Answer : Answer: A

Description : The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Last Answer : Answer: B

Description : What causes counter emf in a dc motor

Last Answer : Generator action.

Description : A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? (A) 100 Volts. (B) 0.1 Volts. (C) 1 Volts. (D) 10 Volts.

Last Answer : Ans: D Given N = 1500 rpm, Φ = 0.4 mWb, Z = 1000, P = 4, & A= 4 Therefore, Eb = NΦPZ / 60 A = 1500 x 0.4 x 4 x 1000 x 10^-3 / 60 x 4 = 60/6 = 10 volts

Description : The illustrated device is a _______. EL-0064 A. full wave bridge rectifier B. half wave bridge rectifier C. solid state voltage regulator D. direct current (DC) filter

Last Answer : Answer: A

Description : The most common source of excitation for synchronous motors is a/an ______________. A. stepup transformer B. half-wave rectifier C. DC supply D. AC supply

Last Answer : Answer: C

Description : In a half wave rectifier the rms value of AC component of the waves (a) Zero (b) Equal to DC value (c) More than DC value (d) Less than DC value

Last Answer : b) Equal to DC value

Description : An AC supply of 230 V is applied to half wave rectifier circuit. A transformer turns ratio is 20 : 1. Find i) Output DC voltage (ii) Peak Inverse Voltage (PIV)

Last Answer : Solution:

Description : A separately excited generator as compared to a self-excited generator (a) is amenable to better voltage con-trol (b) is more stable (c) has exciting current independent of load current (d) has all above features

Last Answer : Ans: d

Last Answer : In a separately excited generator supplying rated load the armature reaction is always present.

Last Answer : A separately excited generator as compared to a self-excited generator is amenable to better voltage control, more stable, has exciting current independent of load current.

Last Answer : Self excited Dc motor have same source of power to armature and field winding

Description : A single phase full-wave half-controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode.  (A) ... to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR.

Last Answer : A single phase full-wave half-controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode. because the converter does not provide for free-wheeling for high values of triggering angles

Description : In a single phase induction motor driving a fan load, the reason for having a high resistance rotor is to achieve (A) low starting torque (B) quick acceleration (C) high efficiency (D) reduced size

Last Answer : In a single phase induction motor driving a fan load, the reason for having a high resistance rotor is to achieve quick acceleration

Description : A stepper motor is (A) a dc motor. (B) a single-phase ac motor. (C) a multi-phase motor. (D) a two phase motor.

Last Answer : Ans: D Stepper motor works on 1-phase-ON or 2-phase –ON modes of operation

Description : Explain concept of back emf in DC machine. State how it governs armature current. 

Last Answer : Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.

Description : In a three phase half wave rectifier feeding resistive load, if the input source is a three phase 4 wire system and line to line voltage is 100 V. The supply frequency is 400 Hz. The ripple frequency at the output is: (1) 400 Hz (2) 800 Hz (3) 1200 Hz (4) None of these

Last Answer : In a three phase half wave rectifier feeding resistive load, if the input source is a three phase 4 wire system and line to line voltage is 100 V. The supply frequency is 400 Hz. The ripple frequency at the output is: 1200 Hz

Description : In a 3-phase half-wave rectifier, if per phase input is 200 V, then the average output voltage is   (a) 233.91 V (b) 116.95V (c) 202.56 V (d) 101.28V 

Last Answer : a

Description : An a.c. tachometer is just a ________with one phase excited from the carrier frequency. (A) two-phase A.C. servomotor (B) two-phase induction motor (C) A.C. operated universal motor (D) hybrid stepper motor.

Last Answer : Ans: D This is a special purpose machine whose stator coil can be energized by electronically switched current.

Description : Which one of the following is the advantage of connecting two dry cells in parallel instead of in series? Is it because the parallel arrangement: w) gives twice the EMF of one dry cell x) has no ... circuit half as fast as would a single cell z) has half the internal resistance of a single cell

Last Answer : ANSWER: Z -- HAS HALF THE INTERNAL RESISTANCE OF A SINGLE CELL 

Description : (a) Define permeability. (b) Define MMF. (c) Define form factor of an alternating quantity. (d) Define frequency and time period of an alternating quality. (e) Define transformation ratio of transformer. ... and state the meaning of each term used. (g) Give two applications of single phase motors. 

Last Answer : Permeability : It is the ability of a magnetic/Non magnetic material to allow setting up of flux in it.  MMF : The magneto motive force (MMF) is the force required to setup flux in a magnetic / ... applications of single phase motors : Water pumps, ceiling fan, lathe machine