Application of DC Series Motor
Last Answer : 1. Electric traction 2. Cranes, 3. Passenger elevators, 4. Continuous conveyors, 5. Grinders, 6. Polishers,
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149 views
1 answer
asked
May 26, 2020
by
anonymous

separately excited dc motor controlled by chopper with a frequency of 500hz and source voltage of 230v and rated value of motor is 220v 24A 100 rpm find its duty ratio at 1.2 times rated torgue and 500rpm
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0 answers

If field current is decreased in shunt dc motor, the speed of the motor (a) remains same. (b) increases. (c) decreases. (d) none of the above.
Last Answer : increases
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2.8k views
4 answers
asked
Aug 25, 2019
by
anonymous

What would happen if a DC motor was supplied with AC ?
Last Answer : With three phase induction motor, humming and not rotate, but if single phase universal motor like air blower, home mixture, motor run on constant speed..speed variation not possible...
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120 views
2 answers
asked
Aug 18, 2019
by
anonymous

State the function of following parts of DC motor : i) Yoke ii) Poles iii) Field winding iv) Commutator.
Last Answer : Function : i) Yoke: The yoke serves the following two purposes. i) It supports the other components such as poles and provides mechanical protection for whole machine. ii) It forms a part of ... one pole to another and thus to help the motor to develop a continuous and unidirectional torque
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542 views
1 answer
asked
Jul 30, 2019
by
anonymous

DC series motor should never be started at no-load. Justify.
Last Answer : At no load the field current (which is also the armature current) is very small and hence the useful air-gap field flux. Also the torque is very small. As N ∝ 1/Ф the speed rises to ... on the rotating parts they may get damaged. Hence DC series motor should never be started on no-load.
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208 views
1 answer
asked
Sep 18, 2018
by
anonymous

With the help of neat diagrams,explain the following methods of speed control in DC series motor. i) Field diverter method. ii) Armature diverter method.
Last Answer : (i) Field diverter method: - Resistance connected in parallel with field winding -By adjusting this resistance current can by diverted from field winding -Thus field current decreases and the speed can be ... decreased, the flux must increase and hence speed is decreased than the rated speed.
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237 views
1 answer
asked
Sep 18, 2018
by
anonymous

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.
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206 views
1 answer
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Sep 18, 2018
by
anonymous

Last Answer : Principle of operation of a dc motor: When a current carrying conductor is placed in a magnetic field, the conductor experiences the mechanical force. The magnitude of force is given by F = BIL newton where F – Force , B – Maximum flux density , I – Current , L – Active length of conductor
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66 views
1 answer
asked
Sep 18, 2018
by
anonymous

Give the two functions of yoke in DC motor.
Last Answer : Functions of yoke in DC motor: 1) Provides mechanical support for poles. 2) Acts as protecting cover for machine. 3) Provides path for magnetic flux.
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809 views
1 answer
asked
Sep 18, 2018
by
anonymous

State any two applications of brushless DC motor.
Last Answer : 1) Synthetic fibre drawing works. 2) Turn table drives in record players. 3) Spindle drives in hard disk circuits. 4) Computer peripheral equipments as plotters etc. 5) Gyroscope motors. 6) Biomedical machines as heart pumps.
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96 views
1 answer
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Sep 16, 2018
by
anonymous

With the help of necessary sketch, explain in brief the working of brushless DC motor.
Last Answer : Constructional Diagram of Brushless DC Motor: Working of brushless DC motor: The brushless DC motor is the combination of a permanent excited synchronous motor and a frequency ... Suitable PWM techniques allow regenerative breaking, which increases dynamic and efficiency of the drive.
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77 views
1 answer
asked
Sep 15, 2018
by
anonymous

List the various losses on a DC Motor.
Last Answer : The various losses on a DC Motor: 1) Winding losses (Copper losses): i) Armature winding losses ii) Shunt field losses iii) Series field losses 2) Core losses (iron losses): 3) Brush contact losses: 4) Windage and frictional (Mechanical losses):
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60 views
1 answer
asked
Sep 15, 2018
by
anonymous

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
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231 views
1 answer
asked
Apr 30, 2018
by
anonymous

In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these
Last Answer : In a DC motor, it is important to place the brushes along Magnetic Neutral Axis
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96 views
1 answer
asked
Apr 29, 2018
by
anonymous

In a 4-pole wave winding connected dc motor, the cross-magnetizing AT/pole for a brush shift of θ radians (A) Armature amp-conductors × (θ/360o) (B) Armature amp-turns × (θ/360o) (C) Armature amp-conductors × (1/4 - θ/360o) (D) Armature amp-conductors × (1/8 - θ/360o)
Last Answer : In a 4-pole wave winding connected dc motor, the cross-magnetizing AT/pole for a brush shift of θ radians Armature amp-conductors × (1/8 - θ/360o)
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124 views
1 answer
asked
Apr 28, 2018
by
anonymous

In a differentially compounded dc motor (A) the speed is constant as the torque increases (B) the speed falls non-linearly as the torque increases (C) the speed increases non-linearly as the torque increases (D) the flux increases as the load increases
Last Answer : In a differentially compounded dc motor the speed increases non-linearly as the torque increases
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82 views
1 answer
asked
Apr 25, 2018
by
anonymous

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
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169 views
2 answers
asked
Apr 25, 2018
by
anonymous

A DC shunt motor having unsaturated magnetic circuit runs at 1000 rpm with rated voltage If the applied voltage is reduced to half of the rated voltage, the motor will run at (A) 2000 rpm (B) 1000 rpm (C) 750 rpm (D) 500 rpm
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281 views
0 answers
asked
Apr 14, 2018
by
anonymous

To enable dc series motor work satisfactory with an AC supply, the following modifications should be done (1) The yoke and poles should be completely laminated (2) The poles should be made of ... (3) The air gap between stator and rotor be reduced (4) Compensating poles should be introduced
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asked
Apr 11, 2018
by
anonymous

A dc series motor when connected across an AC supply will (1) Develop torque in same direction (2) Not develop any torque (3) Draw dangerously high current (4) Develop a pulsating torque
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90 views
0 answers
asked
Apr 11, 2018
by
anonymous

A dc shunt motor runs at 500 r.p.m at 220 V. A resistance of 4.5 Ω is added in series with the armature for speed control. The armature resistance is 0.5 ohms. The current to stall the motor will be (1) 44 A (2) 50 A (3) 44.4 A (4) 60 A
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198 views
0 answers
asked
Apr 11, 2018
by
anonymous

The dc motor used for intermittent high torque loads is (1) dc series motor (2) dc shunt motor (3) differential compound motor (4) cumulative compound motor
Last Answer : 4 cumulative compound motor
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542 views
1 answer
asked
Apr 10, 2018
by
anonymous

A cumulative dc compound motor runs at 1500 rpm. on full load. If its series field is short-circuited, its speed (1) becomes zero (2) remains unchanged (3) increases (4) decreases
Last Answer : Increases. As it's cumulative compound motor, both series and shunt field both assist each other. If series field is short circuited, the overall field strength will decrease and atop of that ... speed is inversely proportional to field strength. So, the speed will increase overall.
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531 views
1 answer
asked
Apr 10, 2018
by
anonymous

If the back emf of a dc motor is doubled and its speed is also doubled, the torque developed in the machine will (1) get doubled (2) become 4 times (3) get halved (4) remain unaltered
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189 views
0 answers
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Apr 10, 2018
by
anonymous

The method of speed control used for increasing the speed of a dc shunt motor above its rated speed is 1) armature resistance control 2) field control (3) armature voltage control (4) series parallel control
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0 answers
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Apr 10, 2018
by
anonymous

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
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1.2k views
1 answer
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Apr 10, 2018
by
anonymous
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Variation in dc excitation of a synchronous motor causes variation in (a) Speed of motor (b) Power factor (c) Armature current (d) Both armature current and power factor
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0 answers
asked
Apr 10, 2018
by
anonymous

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.
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279 views
1 answer
asked
Apr 9, 2018
by
anonymous

A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, having a flux of 0.4 mWb and total number of conductors 1000. The value of e.m.f. will be: (A) 100 Volts (B) 0.1 Volts (C) 1 Volts (D) 10 Volts
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617 views
0 answers
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Apr 9, 2018
by
anonymous
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A 750 Hp, 250 V, 1200 r/min DC motor is connected to a 208 V, 3 phase, 60 Hz, line using a 3 phase bridge converter. The full load armature current is 2500 A and the armature resistance is 4 m ohm. Calculate ... angle under rated full load conditions. (A) 45 deg (B) 208 deg (C) 27 deg (D) 32 deg
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0 answers
asked
Apr 5, 2018
by
anonymous

If the load current and flux of a DC motor are held constant, and voltage applied across its armature is increased by 10%, its speed will: (A) Decrease by 10%. (B) Remain unchanged. (C) Increase by 10%. (D) Increase by 20%.
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86 views
0 answers
asked
Apr 5, 2018
by
anonymous

What is the order of the characteristic equation of an armature controlled DC motor? (A) First order equation (B) Second order equation (C) Zero order equation (D) Third order equation
Last Answer : third order
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1.1k views
1 answer
asked
Apr 5, 2018
by
anonymous

Which type of starter is used to start the DC motor?
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77 views
0 answers
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Mar 15, 2018
by
anonymous

What are the advantages of DC series motor?
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92 views
0 answers
asked
Mar 15, 2018
by
anonymous

Why dc series motor should not be started at no load?
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629 views
0 answers
asked
Mar 15, 2018
by
anonymous

Why a dc series motor has a high starting torque?
Last Answer : motor
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86 views
1 answer
asked
Mar 15, 2018
by
anonymous

What is the principle of DC motor?
Last Answer : principle
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95 views
1 answer
asked
Mar 15, 2018
by
anonymous

What is the back EMF of a dc motor?
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2.6k views
0 answers
asked
Mar 15, 2018
by
anonymous

Last Answer : Fleming's left hand rule.
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114 views
1 answer
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Sep 27, 2017
by
anonymous

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

Selecting a correct DC stepper motor for a project?
Last Answer : You will need to calculate the moment of inertia of the shaft you are turning so you can determine the required torque. You will get that after you determine the peak acceleration from the velocity ... Once you have acceleration, displacement, and moment of inertia you can size the motor for power.
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1 answer
asked
Mar 2
by
anonymous

What is DC Motor ?
Last Answer : : An electric motor that receives electricity from a DC power source is therefore a DC motor.
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1 answer
asked
Jan 28
by
anonymous

What battery is recommended with a 3 volt DC motor?
Last Answer : Need answer
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1 answer

Why is it dangerous yo supply power to an unloaded series connected dc motor?
Last Answer : Need answer
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1 answer

If the supply voltage is 220 volts 60 Hz, what is the operating voltage of the motor controller circuitry illustrated? EL-0011 A. 110 volts DC B. 110 volts AC C. 220 volts DC D. 220 volts AC
Last Answer : Answer: D
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1 answer

When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt ... C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing
Last Answer : Answer: B
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1 answer

Sparking at the brushes of a DC propulsion motor can be the result of ____________. A. improper brush pressure B. improper brush seating C. reversed interpole polarity D. all of the above
Last Answer : Answer: D
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1 answer

Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer
Last Answer : Answer: D
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1 answer

The torque produced by a DC motor armature is the product of the force acting at the armature surface multiplied by _____________. A. work done by the armature in one revolution B. effective ... arm at the center of rotation of the armature D. perpendicular distance to its center of rotation
Last Answer : Answer: D
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