(A)-Correct the false statements - It is not possible to increase the speed of a shunt DC motor above rated using flux field control -The main disadvantage of potential divider control method of shunt DC motor, the speed up to zero is not possible. -The armature voltage of series DC generator is not affected by field current. A - To solve the armature reaction Problem in large machines, this can be achieved by increasing the brush width -In shunt d-c generator the field winding will be constructed from high number of turns and high cross-sectional area of wire.

(A)-Correct the false statements - It is not possible to increase the speed of a shunt DC motor above rated using flux field control -The main disadvantage of potential divider control method of shunt DC motor, the speed up to zero is not possible. -The armature voltage of series DC generator is not affected by field current. A - To solve the armature reaction Problem in large machines, this can be achieved by increasing the brush width -In shunt d-c generator the field winding will be constructed from high number of turns and high cross-sectional area of wire.

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

See similar textbooks

Similar questions

6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor
1) P.f of inductive load is corrected by connecting . . across it. .... ...... 2) Open circuit test measures . losses. 3) The output variables of a motor are and ........ ... .... 4) For a motor output power is given by ...... 5) Flux control, voltage control, and armature control are three methods for ....... of dc motor. 6) A transformer takes 100V at primary and gives 50V at secondary, its turn ratio equals 7) The given set of equations represents . . Ea – laRa = Vr , la = IL , %3D Rf 8) The given set of equations represents. la = !, + IL, VT Rf Ea – laRa = Vr , 9) The given set of equations represents . Ea – laRa – IseRse = Vr, la = Ise = l, %3D | 10). .. has more initial torque than shunt dc motor.
L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no
What is the disadvantage of slip ring induction motor...?
A 220 V DC series motor runs drawing a current of 30 A from the supply. Armature and field circuit resistances are 0.4 and 0.1 respectively. The load torque varies as the square of the speed. The flux in the motor may be taken as being proportional to the armature current. To reduce the speed of the motor by 50% the resistance in ohms that should be added in series with the armature is
Q4) What is the effect in series motor if you assume V = Eb , with low resistance fielding winding ? a) b) The given information about series motor on full – load (with that the flux is proportional to the field current) is a ) takes ( 78A) and runs at (850 r.p.m) , the series winding resistance is (0.04 2) , with diverter in parallel with the field winding is a (0.18 2) and the armature resistance is (0.09 S2). ( 220 V Neglected the iron, friction and windage losses. Determine the efficiency , speed when developing full load torque ,the maximum efficiency .
In DC shunt generator the type of current flows in field winding is AC whereas in armature winding it is DC. * True O False If the field winding of a DC shunt motor gets disconnected while in normal operation the speed will decrease to a tremendously low value and the motor may get stop. * True O False A DC series generator is considered suitable for general electric supply. * True False
A PWM signal is sent to a permanent magnet DC motor through an H-bridge circuit. The PWM frequency is 100 kHz, the DC voltage source is 16 volts, and the specification of the motor is given as: voltage = 16 volts, no load speed = 1500 RPM, holding torque = 2 Nm. a. Draw the voltage signal delivered to the motor when the duty cycle is 20% and 80% (at least draw for 5 periods). Calculate the speed of DC motor when the duty cycle is 20% and 80%. b. C. Estimate the output power when the duty cycle is 20% and 80%. Assume that the motor efficiency is 100%.
1- To control the speed of an induction motor, the supply frequency is reduced by 10%. For the same magnetizing current to remain constant, the supply voltage must be....... a) Reduced by 10%, b) Reduced by 20%, c) Increased by 10%, d) Increased by 20% 2. When maximum starting torqua ic ohtoinod
Reducing the supply voltage so that Vnew = Vold / V3 reduces the maximum torque of the motor so that Tmaxnew= ...Tmaxold . * .... ...
what are the disadvantages of slip ring induction motor?
Assume that a separately excited shunt de machine has a rated terminal voltage of 230 V and a rated armature current of 100 A. Its armature winding resistance, commutating winding resis- tance, and compensating winding resistance are 0.08, 0.01, and 0.00842, respectively. The resis- tance of external wires (i.e., R…) is 0.00242. Determine the following: (a) The induced armature voltage if the machine is operating as a generator at full load (b) The induced armature voltage if the machine is operating as a motor at full load