Description : 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.
Description : What is brushless DC motor?
Last Answer : An inverter fed trapezoidal permanent magnet AC motor drive operating in self-controlled mode is called brushless dc motor.
Description : What is Brushless DC Motor (BLDC) ?
Last Answer : Brushless DC Motor (BLDC) The motor is made up of rotor and stator . In BLDC motor the rotor is a ferromagnetic material (permanent magnet). The rotor may be ... winding gives low torque at low speed and start winding gives high torque at low speed.
Description : Advantages and Disadvantages of Permanent Magnet Brushless DC (PMBLDC) Motor
Last Answer : Advantages and Disadvantages of Permanent Magnet Brushless DC (PMBLDC) Motor
Description : Where can I learn how to repair a brushless motor?
Last Answer : You can actually learn how to repair a brushless motor online. First for some background and tips read this message board string (http://www.rcgroups.com/forums/showthread.php?t=419334). There are also ... that show you how to begin fixing your motor (http://www.youtube.com/watch?v=I6GCyLm7mIw)
Description : State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.
Last Answer : Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows: 1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine
Description : State any four applications of DC shunt motor.
Last Answer : Applications of DC shunt motor: 1) Lathe machines 2) drilling machines 3) milling machines 4) Printing machinery 5) Paper industry 6) centrifugal and reciprocating pumps 7) blowers 8)fans
Description : The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor.
Last Answer : (B) a dc shunt motor.
Description : DC Motor Applications in Industries
Last Answer : In spite of wide use of ac supply, dc machines have some advantages compared to ac motors and are used in industries for some applications. Some of the applications where dc motors employed ... , conveyers, heavy planers, for shears and punches, for intermittent high torque loads and air compressors
Description : Is there anywhere in Edinburgh, Scotland, I can buy brushless motors?
Last Answer : It appears that Claremont Electric Motors and AD Auto Electrics are two places that would either carry brushless motors or at least provide you with information on where you can buy brushless motors.
Description : Why brushless screwdriver is more preferred over brush screwdriver. From where we can buy best electric screwdriver.?
Last Answer : Brushless screwdriver has low noise low vibration and do not have the sparking issue . Brush screwdriver may give low torque after carbon brush damage.We can get best electric screwdriver from Microntech engineers . They provide kilews screwdriver
Description : Which of the following statements, concerning the general maintenance of a brushless generator, is correct? A. Paint should be applied to insulating surfaces on an annual basis. B. Alcohol should be used to ... . D. Accessible generator parts should be wiped with a clean dry rag on a periodic basis.
Last Answer : Answer: D
Description : Brushless generators are designed to operate without the use of ___________. A. brushes B. slip rings C. commutators D. all of the above
Description : What are the parts of a brushless AC generator?
Last Answer : Yoke, armature, stator, rotor, primary exciter, main exciter, rotary diode rectifier assembly, impeller, bearing & housing, end cover, terminal block, AVR.
Description : 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
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
Description : State working principle and applications of servo motor.
Last Answer : Working Principle of Servo Motor: Basically servo motor is made up of DC motor, which is controlled by a potentiometer and some gears. Its angle of rotation is controlled by the duration of ... Packaging 6) Woodworking 7) Textiles 8) Printing 9) Robotics 10) Portable drilling 11)Process control
Description : State any four applications of regulated DC power supply.
Last Answer : * Amplifiers * Mobile Phone power adaptors * Regulated power supplies in appliances * Various oscillators
Description : 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.
Description : Application of DC Series Motor
Last Answer : 1. Electric traction 2. Cranes, 3. Passenger elevators, 4. Continuous conveyors, 5. Grinders, 6. Polishers,
Description : 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
Description : 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...
Description : 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.
Description : 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.
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 : 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):
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 : 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
Description : 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)
Description : 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
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 : 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
Description : 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.
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 : 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 : 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
Description : Why a dc series motor has a high starting torque?
Last Answer : motor
Description : What is the principle of DC motor?
Last Answer : principle
Last Answer : There are three types of self excited DC motor 1. series wound 2. shunt wound 3, compound wound 1.Applications of DC series motor are : DC ... DC compound motor is use for punches. These are some applications of DC compound motor.
Last Answer : Fleming's left hand rule.
Last Answer : Self excited Dc motor have same source of power to armature and field winding
Description : applications of each: i) Universal motor ii) Stepper motor.
Last Answer : i) Applications of Universal motor: 1) portable drills 2) hair dryers 3) grinders 4) mixers 5) table-fans 6) blowers 7) polishers 8) Kitchen appliances ii) Applications of Stepper motor ... 7) robotics 8) CNC machine 9) Control systems 10) Biomedical applications 10) XY recorder 11) plotters
Description : Which of the following motor would suit applications where constant speed is absolutely essential ? (A) Brushless dc motor (B) Disk motor (C) Permanent -magnet synchronous motor (D) Stepper motor
Last Answer : stepper motor
Description : The most suitable motor for low power applications is a/an: (A) dc series motor (B) dc shunt motor (C) ac two-phase induction motor (D) ac series motor
Last Answer : The most suitable motor for low power applications is a/an: dc shunt motor
Description : An across-the-line starter is typically used for which of the following applications? A. Reduced-current starting of large motors B. Low torque starting of small motors C. Low resistance starting of DC motors D. Full-voltage starting of motors
Description : What are the applications of dc chopper?
Last Answer : Chopper provides a. High efficiency b. Smooth acceleration c. Fast dynamic response d. Regeneration
Last Answer : a. Battery operated vehicles b. Traction motor control in electric traction c. Trolly cars d. Marine hoists e. Mine haulers f. Electric braking.
Description : State at least one function and the material used for the following parts of DC Motor.
Last Answer : Part Function Material Yoke -Provides mechanical support for poles -Acts as protecting cover for machine -Provides path for magnetic flux Cast Iron OR Cast Steel Field Winding - ... Pole core Provides mechanical support to field winding. Cast Iron OR Cast Steel
Description : State the function of overload coil and No volt coil in dc motor starter.
Last Answer : Function of Overload Coil: When DC motor is overloaded, the overload coil carries the overload current and produces strong magnetic field to attract a plunger, which short the terminals of ... dc motor is prevented from restarting automatically on recovery of supply without starter and protected.
Description : State two applications of 1) Shaded pole motor 2) Universal motor
Last Answer : (i)Applications of Shaded pole motor: 1. Small fans 2. Toy motors 3. Hair dryers 4. Ventilators 5. Electric clocks 6. Record players 7. Motorized valves 8. Gramophones 9. Photocopying ... 5. Portable Drilling Machines 6. Electric Shavers 7. Mechanical computing Machines 8. Machine Tools etc.