Answer :
The speed of a universal motor is usually reduced by using gearing.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed/load characteristics of a universal motor is same as that of D.C. series motor.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed control of universal motor used for sewing machines is by varying the resistance.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a universal motor is generally reduced by using gear trains.
asked
Mar 20, 2018
by
anonymous
Answer :
A universal motor can run on either A.C. or D.C.
asked
Mar 20, 2018
by
anonymous
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.
asked
Aug 17, 2019
by
anonymous
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
asked
Aug 17, 2019
by
anonymous
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.
asked
Jul 26, 2019
by
anonymous
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.
asked
Jul 20, 2019
by
anonymous
Answer :
Sparking, is discouraged in a D.C. motor because commutator gets damaged.
asked
Mar 20, 2018
by
anonymous
Answer :
Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.
asked
Mar 20, 2018
by
anonymous
Description : The function of a brush and commutator arrangement in a dc motor is to (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking
Answer :
The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque
asked
Apr 29, 2018
by
anonymous
Description : A universal RLC bridge uses?
Answer :
A universal RLC bridge uses Maxwell Wein bridge for measurement of inductance and modified De Santy's bridge for measurement of capacitance.
asked
Mar 21, 2018
by
anonymous
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)
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)
asked
Apr 28, 2018
by
anonymous
Answer :
If a single phase induction motor runs slower than normal, the most likely defect is worn bearings.
asked
Mar 20, 2018
by
anonymous
Description : For using regenerative breaking, the most suitable motor is : (A) DC series motor (B) Slip ring induction motor (C) Squirrel cage induction motor (D) Synchronous motor
Answer :
For using regenerative breaking, the most suitable motor is : Slip ring induction motor
asked
Apr 29, 2018
by
anonymous
Description : What can cause high amperage on a motor?
Answer :
High amperage can result in a motor when the amount of load increases. when load increases , it reduces the rotor speed which increases the slip at constant synchronous speed ... , as a result more current shall have been drawn to maintain the additional load.
asked
Mar 15, 2018
by
anonymous
Description : Damper winding in a synchronous motor
Answer :
Damper winding in a synchronous motor Serves to start the motor.
asked
May 8, 2018
by
anonymous
Description : In a double squirrel cage induction motor, good starting torque is produced as (A) Large current flows through the outer high resistance winding. (B) Large current flows through the inner high resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.
Answer :
In a double squirrel cage induction motor, good starting torque is produced as Large current flows through the outer high resistance winding.
asked
May 8, 2018
by
anonymous
Description : A change of 4% in the supply voltage to an induction motor will produce a change of approximately
Answer :
A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque
asked
May 8, 2018
by
anonymous
Description : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :
Answer :
In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075
asked
Apr 29, 2018
by
anonymous
Description : In a split-phase induction motor, the resistance/reactance ratios of windings are such that (A) current in the auxiliary winding leads the current in the main winding (B) current in the auxiliary winding lags the current in the main winding (C) both windings develop the same starting torque (D) both windings develop high starting current
Answer :
In a split-phase induction motor, the resistance/reactance ratios of windings are such that current in the auxiliary winding leads the current in the main winding
asked
Apr 28, 2018
by
anonymous
Description : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then (A) the flux is constant (B) the flux first decreases and then increases in the same direction (C) the flux increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor
Answer :
In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then the flux first decreases and then increases in the same direction
asked
Apr 28, 2018
by
anonymous
Description : In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is (A) 0.2 Ω (B) 0.3 Ω (C) 0.4 Ω (D) 0.5 Ω
Answer :
In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is 0.3 Ω
asked
Apr 28, 2018
by
anonymous
Answer :
In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.
asked
Mar 20, 2018
by
anonymous
Description : As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?
Answer :
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.
asked
Mar 20, 2018
by
anonymous
Answer :
In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.
asked
Mar 20, 2018
by
anonymous
Answer :
In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. shunt motor, speed is independent of armature current.
asked
Mar 20, 2018
by
anonymous
Answer :
The starting winding of a single-phase motor is placed in stator.
asked
Mar 20, 2018
by
anonymous
Answer :
In a A.C. series motor armature coils are usually connected to commutator through resistance.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.
asked
Mar 20, 2018
by
anonymous
Answer :
In a ceiling fan employing capacitor run motor secondary winding surrounds the primary winding.
asked
Mar 20, 2018
by
anonymous
Answer :
In a hysteresis motor, the rotor must have retentivity.
asked
Mar 20, 2018
by
anonymous
Description : In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times
Answer :
In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth
asked
May 1, 2018
by
anonymous
Answer :
In variable speed motor a weaker commutating field is needed at low speed than at high speed.
asked
Mar 20, 2018
by
anonymous
asked
Mar 20, 2018
by
anonymous
Answer :
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because it has low starting as well as running currents at relatively high power factor.
asked
Mar 20, 2018
by
anonymous
Answer :
In repulsion motor, zero torque is developed when brush axis coincides with the field axis and brush axis is 90° electrical to field axis.
asked
Mar 20, 2018
by
anonymous
Answer :
The purpose of stator winding in the compensated repulsion motor is to improve power factor and provide better speed regulation.
asked
Mar 20, 2018
by
anonymous
Answer :
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it helps in reducing the tendency of the rotor teeth to remain under the stator teeth.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In repulsion motor, maximum torque is developed when brush axis is at 45° electrical to the field axis.
asked
Mar 20, 2018
by
anonymous
Answer :
In split phase motor main winding is of thick wire placed at the bottom of the slots.
asked
Mar 20, 2018
by
anonymous