AC DC Drives Ch 4 - 6 True/False

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Typically, dual-voltage, 3Φ motors have 12 leads coming out of the motor box.

False (Page 107)

DC motors require less maintenance than AC motors.

False (Page 109)

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.

False (Page 109)

The wires extended from the series coil of a DC motor are marked A1 and A2.

False (Page 110)

The voltage of a control circuit is higher than the rating of the motor in most motor control circuits.

False (Page 127)

Reduced-voltage starting of large horsepower motors typically causes problems in power distribution systems.

False (Page 131)

Some electric motor drives allow control functions to be controlled through standard communication ports such as RS-202C ports.

False (Page 131)

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.

False (Page 136)

Typically, triacs are used as solid-state DC switches.

False (Page 137)

National Electrical Code® 400.7 specifies the minimum information that motor manufacturers must provide on the nameplate of a motor.

False (Page 153)

Continuous duty cycle motors are marked INTER on the nameplate of a motor.

False (Page 155)

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.

False (Page 156)

Line frequency is the number of complete electrical cycles per minute of a power source.

False (Page 158)

Temperature rise is the temperature of the air surrounding a piece of equipment.

False (Page 159)

An adjustable motor base complicates the installation of a motor and the tensioning of belts or chains.

False (Page 163)

Belt deflection must equal 1/16" per inch of shaft center-to-center distance.

False (Page 168)

A rotor is the stationary part of an AC motor that produces a rotating magnetic field.

False (Page 94)

Shaded-pole motors produce high starting torque.

False (Page 98)

A shaded-pole motor is an AC motor that has running and starting windings.

False (Page 99)

A capacitor motor is similar in design to a split-phase motor.

True (Page 100)

When connecting a dual-voltage motor, the higher voltage is usually preferred.

True (Page 104)

A DC shunt motor is a motor with the field connected in parallel with the armature.

True (Page 110)

A pigtail is an extended, flexible connection or braided copper conductor.

True (Page 110)

A separately excited shunt field is a shunt field connected to a different power supply than the armature.

True (Page 111)

Direct hard wiring is the most straightforward and oldest motor control method.

True (Page 123)

A locked rotor is the condition in which a motor is loaded so heavily that the motor shaft cannot turn.

True (Page 125)

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.

True (Page 126)

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.

True (Page 128)

DC drives control speed by varying the amount of voltage and current on the field and armature of the motor.

True (Page 129)

Autotransformer starting is a motor starting method that uses a tapped 3Φ autotransformer to provide reduced-voltage starting.

True (Page 134)

Electric motor drives are programmed to apply a voltage boost at low motor speed to compensate for the power loss of a motor.

True (Page 139)

Fans and pumps are typically classified as variable torque/variable horsepower loads.

True (Page 139)

Typically, the control voltage used by electric motor drives is a low voltage, 24 VDC.

True (Page 141)

Analog input devices/signals connected to electric motor drives include potentiometers and variable voltage inputs.

True (Page 142)

The nameplate of a motor includes the name of the manufacturer.

True (Page 153)

Electric motor drive manufacturers build drives to sizes that follow the standard horsepower ratings of motors.

True (Page 155)

When a dual voltage rated motor is used, the higher voltage is preferred.

True (Page 159)

Each National Electrical Manufacturers Association (NEMA) design class of motor has different starting torque values.

True (Page 162)

The most common belt used for power transmission is the V-belt.

True (Page 167)

Angular misalignment is misalignment caused by two shafts that are not parallel.

True (Page 168)

Humidity is considered an environmental condition that affects the operation of a motor.

True (Page 168)

Moving a motor or placing shims under the feet of a motor often corrects alignment problems.

True (Page 168)

The speed (rpm) of a DC motor is proportional to the voltage applied to the motor.

True (Page 92)

Line frequency is the number of cycles per second of the supplied voltage.

True (Page 94)

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.

True (Page 94)


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