NCCER Electrical Module 2 Level 2 Motors Theory and Application Exam Questions and Answers.

NCCER Electrical Module 2 Level 2 Motors Theory and Application Exam Questions and Answers. How DC motors operate? - correct answer -Magnetic lines of force are continuous and always form closed loops; Magnetic lines of force do not cross. Armature: (Definition) - correct answer -The rotating windings of a DC motor. The ____ is a movable electromagnet located between the poles of another fixed permanent (field) magnet as shown. - correct answer -Armature A twisting force called ______ must be developed. _____ is produced by mounting a loop in a fixed magnetic field and as long as the fields of the magnet and armature interact. - correct answer -Torque Commentator: (Definition) - correct answer -A device used on electric motors or generators to maintain a unidirectional current. In the neutral plane, no ____ is produced and the rotation of the armature should stop - correct answer -Torque A _____ is produced by the fields poles, and a loop of wire in the armature turns and cuts this magnetic field. - correct answer -Magnetic field CEMF - correct answer -Counter electromotive force (CEMF) Horsepower: (Definition) - correct answer -The rated output capacity of the motor. It is based on breakdown torque, which is the maximum torque a motor will develop without an abrupt drop in speed. Horsepower: (Equation) - correct answer -Hp= Watts/746 Types of DC motors - correct answer -Shunt Series Compound Types of AC motors - correct answer -Synchronous and Induction (Single and Polyphase) Periodic duty: (Definition) - correct answer -Intermittent operation at a substantially constant load for a short and definitely specified time. Revolutions per minute (rpm): (Definition) - correct answer -The approximate full-load speed at the rated power line frequency. The speed of a motor is determined by the number of poles in the winding. Rotation: (Definition) - correct answer -For single-phase motors, the standard rotation, unless otherwise noted, is counterclockwise facing the lead or opposite shaft end. All motors can be reconnected at the terminal board for opposite rotation unless other wise indicated. Synchronous speed: (Definition) - correct answer -The speed of the revolving field of the stator, which is dependent on the supply frequency and number of poles in a stator winding. Field poles: (Definition) - correct answer -The stationary portion of a DC motor that produces the magnetic field. The name of the motor part that rotates during operation is the ____. - correct answer -Armature The principle reason for developing the brushless DC motor was to ___. - correct answer -eliminate commutator problems The electrical energy required to produce 1hp of mechanical energy is _____. - correct answer -746W When there is a wide variation in both torque and speed requirements, such as a blower or hoist, use a _____. - correct answer -series DC motor The name of the stationary motor part that produces the magnetic field during operation is the ____. - correct answer -stator The rpm of a 60Hz motor with two poles is ___. - correct answer -3,600rpm In three-phase motors, the rotor most commonly used is the _____. - correct answer -squirrel cage rotor The starting torque characteristics of a wound-rotor motor are defined by _____. - correct answer -rotor resistance A three-phase synchronous motor is started with a(n) _____. - correct answer -amortisseur winding The speed of an induction motor depends on the power supply frequency and the ___. - correct answer -numbers of poles The speed on a multiple-winding motor is normally changed by ____. - correct answer -switching contacts in the motor controller A consequent-pole motor has _____. - correct answer -two speeds The method of braking in which DC is applied to the motor windings after AC is removed is known as ____. - correct answer -injection braking Reconnecting a running motor to act as a generator is known as ____. - correct answer -dynamic braking The two primary types of motor enclosures classified by NEMA are ____. - correct answer -open and totally enclosed An open AC squirrel cage motor that makes use of form-wound coils and an insulation system is known as a(n) _____. - correct answer -sealed windings(type) The NEMA frame designation for gasoline pump motors is ____. - correct answer -G