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 A _____ is produced by the fields poles, and a loop of wire in the armature turns and cuts this magnetic field. - ANSWER -Magnetic field CEMF - ANSWER -Counter electromotive force (CEMF) Horsepower: (Definition) - 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) - ANSWER -Hp= Watts/746 Types of DC motors - ANSWER -Shunt Series Compound Types of AC motors - ANSWER -Synchronous and Induction (Single and Polyphase) Periodic duty: (Definition) - ANSWER -Intermittent operation at a substantially constant load for a short and definitely specified time. Revolutions per minute (rpm): (Definition) - 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) - 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) - 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) - 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 ____. - ANSWER -Armature The principle reason for developing the brushless DC motor was to ___. - ANSWER -eliminate commutator problems The electrical energy required to produce 1hp of mechanical energy is _____. - ANSWER -746W When there is a wide variation in both torque and speed requirements, such as a blower or hoist, use a _____. - ANSWER -series DC motor The name of the stationary motor part that produces the magnetic field during operation is the ____. - ANSWER -stator The rpm of a 60Hz motor with two poles is ___. - ANSWER -3,600rpm In three-phase motors, the rotor most commonly used is the _____. - ANSWER -squirrel cage rotor The starting torque characteristics of a wound-rotor motor are defined by _____. - ANSWER -rotor resistance A three-phase synchronous motor is started with a(n) _____. - ANSWER -amortisseur winding The speed of an induction motor depends on the power supply frequency and the ___. - ANSWER -numbers of poles The speed on a multiple-winding motor is normally changed by ____. - ANSWER -switching contacts in the motor controller A consequent-pole motor has _____. - ANSWER -two speeds The method of braking in which DC is applied to the motor windings after AC is removed is known as ____. - ANSWER -injection braking Reconnecting a running motor to act as a generator is known as ____. - ANSWER -dynamic braking The two primary types of motor enclosures classified by NEMA are ____. - 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) _____. - ANSWER -sealed windings(type) The NEMA frame designation for gasoline pump motors is ____. - ANSWER -G