Description : An across-the-line starter provides ___________________. A. maximum torque B. slow starting power C. high speed D. reduced voltage
Last Answer : Answer: A
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
Last Answer : Answer: C
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 : 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
Description : What is the function of the interpoles installed in DC motors? A. To provide greater torque by strengthening the main field. B. To provide sparkless commutation without having to shift the brushes. C. To limit the production of counter-electromotive force. D. To limit the starting surge current.
Last Answer : Answer: B
Description : Moisture accumulating in electric motors and generator windings having a cold insulation resistance greater than 50,000 ohms may be baked out with internal heat. This heat can be developed by ____________. ... an electric welder and feeding it into the armature while running the motor at full speed
Description : As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively ____________ at the start. (A) Lower armature resistance. (B) Stronger series field. (C) Fewer series turns. (D) Larger armature current.
Last Answer : (D) Larger armature current.
Description : Which of the following operating characteristics for DC motors is considered to give high starting torque? A. series B. shunt C. cumulative-compound D. differential-compound
Description : Why do we use capacitor-start induction motors in applications requiring high starting torque in preference to repulsion induction motors?
Last Answer : Capacitors are easily available, cheaper and reliable. Repulsion-induction motors posses a special commutator and brushes that require maintenance. Most manufacturers have stopped making them.
Last Answer : Ans : Capacitors are easily available, cheaper and reliable. Repulsion-induction motors posses a special commutator and brushes that require maintenance. Most manufacturers have stopped making them.
Description : A double squirrel-cage motor is designed to have __________. A. low starting torque B. low starting current C. high starting voltage D. low starting resistance
Description : Excessive heat in an operating motor controller can result from _____________. A. a closed starter contact B. loose connections C. missing arc chutes D. low motor starting torque
Description : Reduced voltage applied to a motor during the starting period will _____________. A. result in decreased acceleration time only B. lower the starting current and increase accelerating time C. cause a greater starting torque D. increase the starting current and pump capacity
Description : The rotor slots of a repulsion-type motor are generally skewed (placed nonparallel to the rotor axis) to _________. A. produce a constant starting torque B. permit a greater air gap with the starter C. permit a smaller air gap with the starter D. reduce eddy current losses
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
Description : Which of the following is a characteristic of fractional horsepower repulsion start motors? A. They start with a rotating stator field. B. The short circuiting ring is removed from the commutator while ... brushes are removed from the commutator while starting. D. They have a low starting torque.
Description : A characteristic of a wound-rotor induction motor, with a high resistance rotor winding, is _____________. A. low starting torque B. high starting torque C. high speed D. low starting voltage
Description : One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for ... placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections
Description : The wiring diagram for the motor starting circuit shown in the illustration indicates ______________. EL-0007 A. resistance starting B. reduced voltage starting C. low voltage protection D. low voltage release
Description : Some large A.C. motors are equipped with with heaters. These could be ___________. I. resistance heaters bolted directly to the frame II. low voltage windings embedded in the motor windings A. I only B. II only C. either I or II D. neither I or II
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
Last Answer : Answer: D
Description : In general, polyphase induction motors can be started on full line voltage by means of ______________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters
Description : Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?
Last Answer : DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.
Description : Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?
Description : In a DC series circuit, all the conductors have the same ____________. A. power expended in them B. voltage drop across them C. resistance to current flow D. current passing through them
Description : If a unloaded shunt motor's field were weakened by rheostat resistance or by an open circuit, the motor would _________. A. overspeed due to reduced CEMF B. stop because of low flux C. continue to run at base speed D. slow down and overheat
Description : The most common source of excitation for synchronous motors is a/an _____________. A. low voltage battery B. motor attenuator set C. DC exciter generator D. AC supply
Last Answer : A direct online starter is used for starting motors up to 5 H.P.
Description : Universal motors will operate on AC or DC current, and are generally found in _____________. A. portable tools B. large pump motors C. turbo electric main motors D. forced draft fans
Description : If an induction motor were to be operated at 90% rated voltage, _____________. A. there would be an increase in starting torque B. starting current would increase slightly C. synchronous speed would decrease slightly D. the slip would increase
Description : What are the effects of increasing rotor resistance on starting current and starting torque?
Last Answer : The additional external resistance reduces the rotor current and hence the current drawn from the supply. It improves the starting torque developed by improving the power factor in high proportion to the decrease in rotor current..
Description : Reduction in the capacitance of a capacitor-start motor, results in reduced (A) Noise. (B) Speed. (C) Starting torque. (D) Armature reaction.
Last Answer : Ans: C Reduction in the capacitance reduces starting voltage, which results in reduced starting torque.
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 : To check the three line fuses of a three-phase system consisting of a three-phase motor, you must _____________. A. place the starter in the 'stop' position B. make sure the motor is operating at full ... leads across the 'hot' ends of the fuses D. place the leads across the bottom ends of the fuses
Description : A characteristic of an induction motor with a low resistance rotor winding is _____________. A. high starting voltage B. high starting current C. high slippage D. low starting voltage
Description : When troubleshooting electronic equipment, you should use a high impedance multimeter ________________. A. to prevent excess current flow through the meter that would damage it B. for AC measurements only ... being tested D. so as not to load down the circuit and obtain erroneous voltage readings
Description : What is the minimum voltage required for starting of 6.6 kV motors?
Last Answer : Minimum 80% of rated voltage.
Description : Motor starter or controller contacts may become welded together if the contacts _____________. A. open too quickly and arc B. close under excessive pressure C. open or close too quickly D. close under excessive starting current
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 : In a 15 HP induction-type motor with a cage rotor, the current required at standstill to produce starting torque is approximately ____________. A. half the full load current B. equal to the full load current C. five times the full load current D. ten to twenty times the full load current
Description : A single-phase induction motor having a relatively high starting torque, is the ___________. A. shaded pole motor B. wound-rotor motor C. capacitor-start motor D. resistance-start motor
Description : Why is the starting torque of a resistance split-phase induction motor not high?
Last Answer : The starting torque is given as, Ts = K Im Is Sin Ф Where K = constant whose magnitude depends upon the design of the motor (i) The angle between Is and Im is small ... Im are not equal in magnitude, the rotating magnetic field is not uniform and the starting torque produced is small.
Description : Low voltage releases as used in some shipboard motor starter and control equipment will have which of the following characteristics? A. They trip circuit contactors when the motor starts to overspeed. B. ... coil of the starter. D. They allow the motor to restart upon restoration of normal voltage.
Description : Shunt, series, and compound wound motors, are all DC motors designed to operate from _____________. A. constant potential, variable current DC sources B. variable potential, constant current DC ... C. variable potential, variable current DC sources D. constant potential, constant current DC sources
Description : Damp armature windings in a D.C. motor may lead to ____________. A. reduced voltage B. reduced current C. increased resistance D. overheating
Description : Which of the following actions must be carried out before a voltage tester can be used to test the three line fuses to a three-phase motor? A. The fuses must be removed from the circuit. B. The ... disconnected and tagged. D. Nothing need be done as long as the motor is running under a light load.
Description : Squirrel cage induction motor has a) Zero starting torque b) Very small starting torque c) Medium starting torque d) Very high starting torque
Last Answer : Ans: B
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
Description : If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced ... speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop