Description : Low horsepower, polyphase, induction motors can be started with full voltage by means of _____________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters
Last Answer : Answer: C
Description : Autotransformer starters or compensators are sometimes used with polyphase induction motors to _____________. A. reduce the voltage applied to the motor during the starting period B. increase the voltage for ' ... to be either stepped up or down, depending on the application, to ensure full torque
Last Answer : Answer: A
Description : Most three-phase induction motors of five horsepower or less, are started by _____________. A. autotransformer starters B. resistor starters C. across-the-line starters D. reactor starters
Description : Most three-phase induction motors used for driving engine room auxiliaries are started by _____________. A. resistor starters B. across-the-line starters C. impedance starters D. reactor starters
Last Answer : Answer: B
Description : Which of the listed types of motor controllers and starters is illustrated? EL-0080 A. Across-the-line B. Primary-resistor C. Autotransformer D. Part-winding
Description : The electrical schematic shown in the illustration represents a/an ____________. EL-0017 A. across-the-line starter B. primary-resistor starter C. autotransformer starter D. part-winding starter
Description : As shown in the illustration, which of the listed types of motor controllers and starters is indicated? EL-0012 A. Across-the-line B. Capacitor C. Autotransformer D. Part-winding
Description : Which of the following types of motors is often designed for use in correcting power factor? A. Polyphase B. Wound-rotor C. Induction D. Synchronous
Last Answer : Answer: D
Description : Across-the-line starters are used with AC motors to provide _____________. A. reduced starting current B. regulated starting current C. high starting torque D. controlled starting acceleration
Description : A resistor placed in parallel to the output of a power supply _____________. A. is a temperature compensator B. corrects power factor C. prevents excessive currents D. aids in output voltage regulation
Description : Which of the following statements is true concerning a polyphase synchronous propulsion motor? A. The motor is started as an induction motor. B. Resistance is gradually added to the rotor circuit. C. ... is held below the rated current. D. The field winding is energized for starting purposes only.
Description : The voltage at the reference electrode of the circuit shown in the illustration is applied to the input of a/an ______________. EL-0090 A. class A detector whose output drives an ... drives an 2-stage isolation transformer D. magnetic amplifier whose output controls a saturable reactor
Description : For practical purposes, in a simple series circuit, the source voltage will be dropped across one resistor if it has ______________. A. half the resistance of the other resistor B. a resistance equal to the other C. at least ten times the resistance of the other D. a partial short circuit
Description : In a simple series circuit, the entire source voltage will drop across ______________. A. the resistor next to the negative terminal B. a short circuit C. the resistor next to the positive terminal D. an open circuit
Description : An advantage of DC motors over AC motors is that they _____________. A. are less expensive B. require less maintenance C. can be started across the line D. offer a more effective means of controlling speed
Description : The function of the autotransformers used with the starters of large AC motors is to provide _____________. A. increased voltage for starting B. increased torque for starting C. reduced voltage for starting D. speed control
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 : If the synchronous speed of a 12 pole, polyphase, induction motor operating at 60 Hz were 600 RPM, how many poles will be required in a similar motor operating at the same frequency but having a synchronous speed of 900 RPM? A. 4 B. 6 C. 8 D. 18
Description : In the illustrated device, the part labeled '1A' _________. EL-0001 A. are start and run windings for a single phase shaded pole induction motor B. is the stator for a polyphase induction ... armature for a squirrel cage rotor motor D. are direct current shunt field windings for a universal motor
Description : In the illustration, the assembly labeled 2 is a ________. EL-0001 A. wound rotor and shaft for a single phase induction motor B. conduction rotor and shaft for a polyphase induction motor C. ... cage rotor and shaft for a polyphase motor D. squirrel cage rotor for a single phase induction motor
Description : What are the types starters used for starting of induction motor?
Last Answer : a. Direct on line starter (air break) mechanically. b. Direct on line starter (air break or oil immersed) electrically. c. Star delta starter. d. Slipring motor starter. e. Auto transformer starter.
Description : Draw the power and control circuit for motors using autotransformer type starter.
Last Answer : Draw the power and control circuit for motors using autotransformer type starter.
Description : In testing a three-phase delta winding for an open circuit using a megohmmeter, you must ______________. A. test each phase with all connections intact B. measure the voltage across the open ... groups to avoid short circuiting D. open the delta-connections to avoid shunting the phase being tested
Description : The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer
Description : Shading coils are installed on AC full-voltage starters to _____________. A. eliminate contact chatter B. dissipate opening contact arcs C. delay current build up in the holding coil D. protect the motor windings from momentary starting current overload
Description : An autotransformer is equipped with a 50% tap, a 65% tap, and an 80% tap. Which of the following statements is true concerning a load connected to the 50% tap? A. The load is ... is receiving maximum voltage and minimum current. D. The load is receiving maximum voltage and maximum current.
Description : What would be the voltage drop across the series resistor of the circuit shown in the illustration if the source is 30 volts, the resistance of R1 is 10 ohms, R2 is 10 ohms and R3 is 10 ohms? EL-0032 A. 5 volts B. 10 volts C. 20 volts D. 30 volts
Description : Which of the following statements concerning a simple parallel resistance circuit is correct? A. The voltage drop across each resistor is the same. B. The total current flow equals the reciprocal ... resistances. D. The total voltage equals the sum of the individual voltages across each resistance.
Description : Routine A.C. motor maintenance should include periodic ______________. A. thermometer readings at normal loads to detect abnormal temperature rises B. inspection of the motor's internals for loose rotor bars ... C. bearing replacement each year using sealed units if available D. all of the above
Description : The most common source of excitation for synchronous motors is a/an ______________. A. stepup transformer B. half-wave rectifier C. DC supply D. AC supply
Description : The advantage(s) of the method of D.C. motor speed control shown in the illustration is/are ______________. EL-0101 A. elimination of armature starting resistor losses B. elimination of speed instability with variable loads C. the ease of reversing motor direction D. all of the above
Description : The purpose of resistor bank 'R1-R5' in the winch circuit shown in the illustration is to ______________. EL-0102 A. limit armature current in lower and 'series field' current in hoist to ... required speeds D. regulate the strength of the brake solenoid 'B1-B2' in both directions of operation
Description : The third color band on a resistor is used to indicate the ______________. A. tolerance of the resistor B. number of zeros following the first two significant figures in the resistance value C. first significant figure of the resistance D. second significant figure of the resistance
Description : Which ofthe following materials is used in the manufacture of resistance grids to be used in the starters of large motors ? (a) Copper (b) Aluminium (c) Steel (d) Cast-iron
Last Answer : (d) Cast-iron
Last Answer : Starters are used with D.C. motors because to restrict armature current as there is no back e.m.f. while starting.
Description : When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. This means the ______________. A. frequency of the incoming ... the bus D. terminal voltage of the incoming alternator is approaching that of the bus
Description : The horizontal line which cuts across 'L1' shown in figure 'A' of the illustration indicates a/an ______________. EL-0091 A. iron core B. saturable core C. air gap D. capacitive coupling
Description : Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under ... A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.
Description : A series wound DC motor has its armature and field connected in series with a resistor. When the motor is disconnected from its power supply, this motor will exemplify __________. A. the ... the proper connections for an automatic strip heater C. a reversing controller circuit D. dynamic braking
Description : The 'reset' contacts of the master switch shown in the illustration are ______________. EL-0102 A. closed only when the master switch is 'off' B. closed only when the master switch selects a 'run' condition C. opened separately by the winch operator D. opened when line voltage drops 10%
Description : A three-phase, squirrel cage, induction motor will run hot due to a/an ______________. A. improper brush position B. reversed commutating pole C. shorted stator D. high power factor
Description : The reversal of an AC, three-phase, induction motor is accomplished by ______________. A. changing all three motor leads B. reversing the position of the slip rings C. interchanging any two of the three motor leads D. interchanging any two brushes
Description : The basic operating principle of a transformer is attributed to ______________. A. electromagnetic induction B. variance of a conductor in a magnetic field C. mutual reaction D. thermionic emission
Description : An ammeter has a full-scale deflection current of 100mA. If the same ammeter is used to measure a full-scale current of 1.0ampere, what is the value of the shunt resistor in ohms if the voltage across the meter is 9.0 volts?
Last Answer : 10 ohms
Description : increases the steady state accuracy. (a) Integrator (b) Differentiator (c) Phase lead compensator (d) Phase lag compensator Ans:A 10.As a result of introduction of negative feedback which of the following will not decrease ? (a) Band width (b) Overall gain (c) Distortion (d) Instability
Last Answer : Ans: A
Description : What component in the telephone set has the primary function of interfacing the handset to the local loop? A. Varistor B. Induction coil C. Resistor D. Capacitor
Last Answer : B. Induction coil
Description : What is the effect of following on induction motors: (1) Voltage unbalance (2) Harmonic distortion
Last Answer : i) Effect of voltage unbalance: For three phase motors this leads to unequal currents in the three phase windings that result in unbalance in the fields produced due to which negative phase ... currents thereon). This leads to motor failures, lower life and improper torque speed characteristics.
Description : State starters used for i) 3-Ph squirrel cage induction motor (3HP) ii) D.C. motor
Last Answer : Name the starters used for following motors : i) 3 H.P. 3-Ph squirrel cage I.M: i) DOL starter OR ii) Star-Delta Starter OR ii) Auto transformer starter OR iii) Soft start starter. ii) D.C Shunt Motor : 1) Armature resistance starter (Three Point Starter) OR 2) Four Point Starter
Description : The speed and torque of induction motors can be varied by which of the following means: 1) Stator voltage control 2) Rotor voltage control 3) Frequency control 4) All of these
Last Answer : All can off them can control speed and torque of induction motor.This is because increased supply frequency increases synchronous speed which will definetly affect torque and speed . .Both stator and rotor voltage control are proportional to torque and slip.