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The speed control of universal motor used for sewing machines is by varying the resistance.

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Answer : Speed control of a universal motor is achieved by varying field flux with tapped field windings, connecting rheostat in series, applying variable voltage by means of silicon controlled rectifier, applying variable voltage by means of variable auto-transformer.

Answer : The speed of a universal motor is usually reduced by using gearing.

Answer : The speed/load characteristics of a universal motor is same as that of D.C. series motor.

Answer : The speed of a universal motor is generally reduced by using gear trains.

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Answer : Series motor has the poorest speed control.

Description : What are the speed control methods of dc motor?

Answer : Field control of DC motor Armature control of DC motor

Description : speed control methods of three phase induction motor?

Answer : Speed control of three phase induction motor

Description : Speed control of the motor using TRIAC

Answer : Speed control of the motor using TRIAC:  This basic phase triggering circuit uses the triac in series with the motor across an AC sinusoidal supply. The variable resistor, VR1 is used ... meaning that it may not trigger at the exact same point for each positive and negative half cycle.

Answer : The wattage of motor for driving domestic sewing machine will be around 100 to 150 W.

Answer : The direction of rotation of universal motor can be reversed the by reversing the flow of current through either armature winding or field winding.

Answer : Speed control by Ward Leonard method gives uniform speed variation in both directions.

Answer : A universal motor is one which can be operated either on D.C. or A.C. supply at approximately the same speed and output.

Answer : In a universal motor, the most common cause of brush sparking is open armature winding, shorted armature winding, shorted field winding, high commutator mica.

Answer : Usually wide and sensitive speed control is desired in case of colliery winders.

Answer : In D.C. machines fractional pitch winding is used to reduce the sparking.

Answer : In Ward-Leonard control the lower limit of speed is imposed by residual magnetism of the generator.

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

Description : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min (A) 100 rpm (B) 200 rpm (C) 400 rpm (D) 800 rpm

Answer : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm

Description : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

Answer : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

Answer : The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.

Answer : For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.

Description : State working principle of universal motor with the help of diagram.

Answer : Working Principle of Universal motor : It is modified DC series motor which can work on AC as well as DC supply. According to basic motor principle, whenever a current carrying conductor is placed in magnetic ... They have nearly same operating characteristic for both AC and DC supply. 

Description : applications of each: i) Universal motor ii) Stepper motor.

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 : State two applications of 1) Shaded pole motor 2) Universal motor

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.

Description : Draw and explain working of universal motor. Give two applications of universal motor.

Answer : Figure of Universal motor:   Operation of universal motor on A.C. and D.C. supply:   *A universal motor works on either DC or single phase AC supply. When the universal motor is ... , regardless of AC or DC supply, universal motor works on the same principle that DC series motor works.  

Answer : A universal motor can run on either A.C. or D.C.

Answer : The armature voltage control of D.C. motor provides constant torque drive.

Description : Armature control of DC motor

Answer : Armature control of DC motor

Description : Field control of DC motor

Answer : Field control of DC motor

Description : Silicon steel is used in electrical machines because it has?

Answer : Silicon steel is used in electrical machines because it has low hysteresis loss.

Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

Answer : In variable speed motor a weaker commutating field is needed at low speed than at high speed.

Answer : As the load is increased the speed of D.C. shunt motor will reduce slightly.

Answer : The speed of a D.C. series motor is inversely proportional to the armature current.

Answer : In a D.C. shunt motor, speed is independent of armature current.

Answer : In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.

Answer : Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.

Answer : Speed torque characteristic of a repulsion induction motor is similar to that of a D.C. compound motor.

Answer : If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.

Description : Why the speed of synchronous motor is constant?

Description : Regulating-transformers are used in power systems for control of

Answer : Regulating-transformers are used in power systems for control of power flow

Answer : The type of D.C. motor used for shears and punches is cumulative compound D.C. motor.

Answer : The motor used for the compressors is capacitor-start capacitor-run motor.

Answer : The shaded pole motor is used for low starting torque.

Answer : The operating speed of a synchronous motor can be changed to new fixed value by changing frequency.

Description : A differentiator is not usually used in control system, because it : - (A) reduces damping  (B) increases error  (C) reduces gain margin  (D) increases input noise

Answer : A differentiator is not usually used in control system, because it : - increases input noise

Description : What are the electromagnetic waves used in remote control?

Answer : The electric motor used in portable drills is universal motor.

Description : Why does the speed of a DC shunt motor decrease as the load increases?

Answer : Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.

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