dc/ac drives chapter 4,5,6
True
A locked rotor is the condition in which a motor is loaded so heavily that the motor shaft cannot turn.
Armature
A(n) ____ is the rotating part of a DC motor.
True
Autotransformer starting is a motor starting method that uses a taped 3 phase autotransformer to provide reduced-voltage starting.
True
Fans and pumps are typically classified as variable torque/variable horsepower loads.
True
Humidity is considered an environmental condition that affects the operation of a motor.
True
Magnetic motor starters include high-power contacts for switching a motor ON and OFF and typically include auxiliary contacts that are used in the control circuit.
electric motor drives
Most ____ provide manual control functins for starting, stopping, jogging, reversing, speeding up, and slowing down directly from the keypad.
Less
Motors that are not fully loaded draw ____ current than rated nameplate current.
False
Reduced-voltage starting of large horsepower motors typically causes problems in power distribution systems.
False
Some electric motor drives allow control functions to be controlled through standard communication ports such as RS-202C ports.
False
Temperature rise is the temperature of the air surrounding a piece of equipment.
Memory
____ are also known as holding or sealing circuits.
Flexible
A(n) ____ coupling allows a motor to operate the driven load while accommodating for a slight misalignment between the motor and load shafts.
Open Motor Enclosure
A(n) ____ is a motor enclosure with openings to allow passage of air to cool the windings.
Magnetic
A(n) ____ is a starter that has an electrically operated switch (contactor) and that includes motor overload protection.
starting
The industrial standard for reversing a 1 phase motor is to reverse the ____ winding.
True
The most common belt used for power transmission is the V-belt.
True
The nameplate of a motor includes the name of the manufacturer.
converter
The section of an electric motor drive that converts AC voltage to DC voltage is the ____ section.
True
The speed (rpm) of a DC motor is proportional to the voltage applied to the motor.
Poles
The speed of an AC motor is determined by the number of ____ in the motor and the frequency of the supply voltage.
manual motor starting
The traditional methods used to provide reduced-voltage starting of large horsepower motors include all of the following except ____.
False
The voltage of a control circuit is higher than the rating of the motor in most motor control circuits.
False
The wires extended from the series coil of a DC motor are marked A1 and A2.
splashproof
Totally enclosed motor enclosures include all of the following except ____.
three
Transistors are ____-terminal electronic switching devices that control current through the device by referencing the amount of applied voltage to the base.
Solid State
Transistors, silicon-controlled rectifiers, triacs, and alternistors are used as ____ switches.
Field Winding
A DC permanent-magnet motor uses magnets, not a coil of wire, for the ____.
True
A DC shunt motor is a motor with the field connected in parallel with the armature.
True
A pigtail is an extended, flexible connection or braided copper conductor.
False
A rotor is the stationary part of an AC motor that produces a rotating magnetic field.
True
A separately excited shunt field is a shunt field connected to a different power supply than the armature.
False
A shaded-pole motor is an AC motor that has running and starting windings.
Delta
A(n) ____ 3 phase motor has each phase wired end to end to form a completely closed loop circuit.
Motor Control
A(n) ____ circuit is a circuit that provides control functions such as starting, stopping, jogging, direction of rotation control, speed control, and motor protection.
False
Belt deflection must equal 1/16" per inch of shaft center-to-center distance.
False
Continuous duty cycle motors are marked INTER on the nameplate of a motor.
United States
In (the) ____, 60 Hz is the standard power source line frequency.
False
Line frequency is the number of complete electrical cycles per minute of a power source.
True
Line frequency is the number of cycles per second of the supplied voltage.
True
Locked in step is a motor condition that occurs when the field of the stator and the field of the rotor are parallel to one another, not allowing the shaft to rotate.
four
Motors with base-to-shaft center distances 3 1/2" or greater have a three- or ____-digit frame number.
True
Moving a motor or placing shims under the feet of a motor often corrects alignment problems.
IEC
NEMA is primarily associated with equipment used in North America and the ____ is primarily associated with equipment used in Europe.
False
National Electrical Code 400.7 specifies the minimum information that motor manufacturers must provide on the nameplate of a motor.
True
Placing contactors and soft starters in parallel allows for soft starting and soft stopping of motors without the need for large heat sinks during motor operation.
False
Shaded-pole motors produce high starting torque.
Increasing
Soft starting is achieved by ____ a motor's voltage gradually in accordance with the setting of the ramp-up control.
Compound
The DC ____ motor is used when high starting torque and constant speed are required.
Synchronous
____ speed is the theoretical speed of a motor based on the number of poles of the motor and line frequency.
Primary Resistor
____ starting is a motor starting method that uses resistors connected in the motor conductors to produce a voltage drop.
Reduced Voltage
____ starting is used to reduce the large current drawn from the power company when full-voltage starting is applied to large horsepower motors.
Centrifugal Switch
A(n) ____ opens to disconnect the starting winding when the rotor reaches a preset speed.
Induction
A(n) ____is a motor that has no physical electrical connection to the rotor because there are no brushes.
T1;T3
Although any two line can be interchanged to change the direction of rotation of a 3 phase motor, the industrial standard is to interchange ____ and ____.
False
An adjustable motor base complicates the installation of a motor and the tensioning of belts or chains.
True
Analog input devices/signals connected to electric motor drives include potentiometers and variable voltage inputs.
True
Angular misalignment is misalignment caused by two shafts that are not parallel.
PLC
Combining a(n) ____ and an electric motor drive allows for maximum control and monitoring of a motor.
False
DC motors require less maintenance than AC motors.
True
Direct hard wiring is the most straightforward and oldest motor control method.
True
Each National Electrical Manufacturers Association (NEMA) design class of motor has different starting torque values.
Voltage
The ____ applied to the stator of an AC motor must be decreased by the same amount as the frequency when controlling speed.
Duty Cycle
The ____ rating of a motor is determined by whether the motor delivers rated horsepower continuously or for short periods of time.
False
The field is the part of the armature that connects each armature coil to the brushes by using copper bars that are insulated from each other with pieces of mica.
True
When a dual voltage rated motor is used, the higher voltage is preferred.
series
When a dual-voltage, wye-connected, 3 phase motor is connected to high voltage, the individual coils of each phase will be in ____.
True
When connecting a dual-voltage motor, the higher voltage is usually preferred.
Parallel
When connecting a dual-voltage, delta-connected, 3 phase motor to low voltage, the individual coils of each phase are in ____
False
When electric motor drives are used to control motors, the type and level of the input supply voltage must match the rated type and voltage level of the motor.
Two
When motor starters are used to perform motor reversing, ____ contactors are required.
True
A capacitor motor is similar in design to a split-phase motor.
2
A capacitor start-run motor uses ____ capacitor(s) for successful operation.
500
DC series motors can develop ____ % of a full-load torque upon starting.
True
Electric motor drive manufacturers build drives to sizes that follow the standard horsepower rating of motors.
AC
Electric motor drives are either AC drives or DC drives, with ____ drives being the most common.
True
Electric motor drives are programmed to apply a voltage boost at low motor speed to compensate for the power loss of a motor.
True
DC drives control speed by varying the amount of voltage and current on the field and armature of the motor.
0.95
Typical service factors include all of the following except ____.
False
Typically, dual-voltage, 3 phase motors have 12 leads coming out of the motor box.
18
Typically, for every ____ F temperature rise above the NEMA rating, the usable service life of a motor is cut in half.
True
Typically, the control voltage used by electric motor drives is a low voltage, 24 VDC.
False
Typically, triacs are used a solid-state DC switches.
Local
When using the ____ method, motor sped is controlled from the keypad of the electric motor drive.
False
Wye-delta motors are specially wound with nine leads extending from the motor to enable the windings to be connected in either a wye or delta configuration.
Name Plate
____ information is used when taking electrical measurements to verify proper operation of a motor or to troubleshoot a problem.
Slip
____ is the difference between the synchronous sped and the actual speed of a motor.
Motor Efficiency
____ is the measure of the effectiveness with which a motor converts electrical energy to mechanical energy.
Parallel
____ misalignment is misalignment caused by two shafts that are parallel but not on the same axis.
Special Purpose
____ motors are used when motors are required to operate in abnormal service conditions such as high ambient temperature or extreme dampness.
