9. The synchronous speed of a three-Phase induction motor depends on the number of magnetic poles in the machine and the actual speed of rotation the actual speed of rotation and the applied Voltage in RMS the actual speed of rotation and number of magnetic poles intensity on the rotating magnetic field and the applied Voltage in RMS frequency of the applied voltage and the number of magnetic poles in the machine

9. The synchronous speed of a three-Phase induction motor depends on the number of magnetic poles in the machine and the actual speed of rotation the actual speed of rotation and the applied Voltage in RMS the actual speed of rotation and number of magnetic poles intensity on the rotating magnetic field and the applied Voltage in RMS frequency of the applied voltage and the number of magnetic poles in the machine

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter30: Dc Motors

Section: Chapter Questions

Problem 3RQ

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This question refers to a three-phase induction motor. which statement are false (A) The slip speed is the synchronous speed minus the rotor speed. (B) As the rotor speed is loaded, the slip decreases. (C) The frequency of induced rotor EMF's increases with load on the rotor (D) The toque on the rotor is due to the interaction of magnetic fields.
2) the armature windings of a 12-pole DC machine are composed of 72 coils with 10 windings, and the windings are 5the layered wave is yellowish. The Rotor speed is 1000 rpm and the flux value per pole is 25mWb.Resistance of Armature windings, commutation windings and compensation windings is 70mΩ, 10mΩ and5mω. (d) calculate the voltage value induced in the machine. (e) DC machine as a foreign (external) excitation generator with a rated current of 100A at full loadif it is started, what is the terminal voltage value? Calculate. (Enter the formulas that you use for calculations and enter the names of the corresponding parameters.)
E-1). The amount of torque developed by a 3-phase squirrel-cage induction motor from no-load to rated-load is_________ proportional to the amount of current flow through the rotor conductors. a) directly b) inversely E-2). If a 3-phase squirrel-cage induction motor were to run at synchronous speed, there would be no relative motion between the rotating magnetic field and the rotor conductors. As a result, there would be no voltage induced in the rotor conductors and no torque developed. a) true b) false E-3). What is the difference between synchronous speed and rotor speed of a 3-phase squirrel-cage induction motor called? a) outrun rpm b) sub-synchronous speed c) slip d) none of the above
P-1).. Which of the following determine the amount of torque produced by a single-phase split-phase motor? a) The strength of the magnetic field of the stator b) The strength of the magnetic field of the rotor c) The phase angle difference between the current in the start winding and the current in the run winding d) all of the above P-2). The phase angle difference between the currents in the start winding and run winding of a single-phase split-phase motor is typically 90 degrees. a) true b) false P-3). A centrifugal switch is used to disconnect the________ winding of a non-hermetically sealed single-phase split-phase motor at approximately 75% of rated speed. a) run b) start c) either "a" or "b" d) neither "a" nor "b" P-4). Where an internal centrifugal switch cannot be used, an external______ relay can be used to perform the same function in a single-phase split-phase motor. a) hot-wire b) current c) solid-state starting d) all of the above
6.a. When the core loss of a synchronous motor is measured, the machine is operatedA. at rated full-load current.B. with excitation and no load.C. at less than rated speed.D. with its brushes lifted off its slip rings.6.b. To calculate the armature current of a synchronous generator, you do NOT need to know itsA. kilovolt-amperes.B. power factor.C. voltage.D. losses.
14.a. The reason for using a laminated stator core in a universal motor is toA. limit the eddy currents and the iron losses.B. limit the saturation of the magnetic circuit.C. maintain a constant level of magnetic flux.D. decrease the doc reactance of the field winding.14.b. If an induction motor has two protective housings for capacitors, it is aA. single-voltage capacitor-start motor.B. permanent-split capacitor-start motor.C. capacitor start-and-run motor.D. dual-voltage capacitor-strut motor.
A 500 V, 6-pole, 50Hz, three phase, 8.5 kW, star connected induction motor has a no load slip of 1.8% and full load slip of 4.5%. Determine the following: (1) The speed of the rotating magnetic flux in r/min. (2) The no-load speed in r/min. (3) The full-load speed in r/min. (4) The frequency of the rotor current at full-load in hertz. (5) The full-load shaft torque in NM.
{Q.1} A three-phase induction motor runs at almost 1198 revolutions per minute (rpm) at no load and 1112 rpm at full load when supplied from a 60-Hz, three-phase source. (a) How many poles does this motor have? (b) What is the slip in percent at full load? (C) What is the corresponding frequency of the rotor currents? (D) What is the corresponding speed of the rotor field with respect to the rotor and with respect to the stator?
A separately excited DC shunt generator produces a no-load voltage of 150 Vdc at 1200 RPM. If the armature resistance is 3 Ohms, calculate the output voltage under the following conditions: (Note all calculations for each problem are to be performed from the base values given above). a) The speed is reduced to 875 RPM. Vout = __________________ b) The field current is increased by 22% (assume a linear field current/flux relationship). Vout = __________________ c) The speed is increased to 1738 RPM Vout = __________________ d) The field current is reduced by 12% and the speed is increased to 1600 RPM Vout = _________________
A 15-kV 35-KVA 0.76-PF-lagging 50-Hz four-pole Y-connected steam-turbine generator has a synchronous reactance of 3.50 Ω per phase and an armature resistance of 0.75 Ω per phase. This generator is operating in parallel with a large power system (infinite bus).a) What is the magnitude of EA at rated conditions?b) What is the generator’s torque angle at rated conditions?c) If the field current is constant, what is the maximum power possible out of this generator? How much reserve power or torque does this generator have at full load? d) Sketch the corresponding phasor diagram and calculate for the armature current (assume the field current is still unchanged) e) At the absolute power possible, how much reactive power will this generator be supplying or consuming?
A 15-kV 35-KVA 0.76-PF-lagging 50-Hz four-pole Y-connected steam-turbine generator has a synchronous reactance of 3.50 Ω per phase and an armature resistance of 0.75 Ω per phase. This generator is operating in parallel with a large power system (infinite bus). a) What is the magnitude of EA at rated conditions? b) What is the generator’s torque angle at rated conditions? c) If the field current is constant, what is the maximum power possible out of this generator? How much reserve power or torque does this generator have at full load? d) Sketch the corresponding phasor diagram and calculate for the armature current (assume the field current IF is still unchanged) e) At the absolute power possible, how much reactive power will this generator be supplying or consuming?
M1. Which of the following is the preferred method of changing the direction of rotation of a DC compound motor? a) by reversing the direction of current flow in the armature conductors b) by reversing the polarity of the magnetic field poles c) either "a" or "b" d) neither "a" nor "b M2. If the resistance of a DC motor's shunt-field circuit is increased, what happens to the speed of the motor? a) it speed decreases b) it stays the same c) it speed increases d) none of the above M3. What is a common method of controlling the speed of a DC shunt motor? a) by adding rheostat in series with the armature b) by adding rheostat in series with the shunt field c) could be either "a" and "b" d) neither "a" nor "b"