Chapter 1 TEST Flashcards
List two examples of controlled variables for motion control applications and two examples from process control applications.
speed Position
Temperature and pressure
An open loop system does not have a
feedback loop
T or F
The basic concept of feedback control is that an error must exist before some corrective action can be made.
True
A pressurized tank must maintain a gas at 325 PSI. A pressure sensor is used to measure the condition of the controlled variable. As the gas cools, the pressure in the tank decreases. When it drops to 300 PSI, a valve is opened, which allows steam to flow to a heat exchanger inside the tank. The additional steam heats the gas and causes pressure to rise.
What is the controlled variable in this process? Gas pressure What is the manipulated variable in this process? Steam flow What is the setpoint? 325 PSI What is the measured variable pressure
Altering the________ variable causes the condition of the ______variable to change
manipulated
controlled
The manipulated variable and controlled variable are synonymous terms in a closed-loop system
FALSE
List another name for each of the following terms.
Motion control
Process control
Batch proces
Servo
Instrumentation / temperature
Sequential Process
The output of the measurement device is called the
Feedback signal
Feed-forward control is seldom used except in combination with feedback control.
True
The control method used in ?servo/process? control applications is to sustain a constant condition of the controlled variable.
process
A DC series motor has____
highest
A cumulative compound motor has__ than a differential compound
higher starting torque
Torque is produced by a motor when the load it is driving
does not move
moves
both
both
In a DC motor, an increasing mechanical load
Increases Armature current
has no effect on armature current Decreases Armature current
Increases Armature current
Work is performed by a motor when the load it is driving ___________ moved a distance.
is not
Is
either answer
fis
When connecting a compound motor for operation, which leads are wired in parallel with the power supply?
A1 - A2
C1 - C2
F1 - F2
S1 - S2
F1 - F2
Which of the following are functions of the brushes and commutator? _________
(choose all that apply)
to provide a path for field current flow
to provide a path for armature current flow to connect and disconnect armature coils in sequence
t provide a path for armature current flow
to connect and disconnect armature coils in sequence
Refer to figure 5-14. work = distance x force
How much work in ft-lb is accomplished when a motor exerts a torque to lift a 473 pound load a distance of 28 feet. Do not include the unit designation ft-lb: example 3250
fr13244.0
Motor efficiency. Percent:efficiency=\frac{power:out}{power:in:}x:100 and power out = hp x 0.746kW
The power consumed by a motor is 10.652 kW , the motor produces 12 hp of output power. Round your answer to 2 decimal places and do not include the symbol %: example 94.52
t84.04
The RPM that the rotating field moves around the Stater is called ____________ (two words )
synchronous speed
In a synchronous motor, the DC excitation is applied to the stator or rotors magnetic field.
rotor’s
To change the rotation of a split-phase AC motor,_______.
reverse the main and auxiliary windings with respect to each other
reverse the power leads
both answers
reverse the main and auxiliary windings with respect to each other
Which components of a DC motor are not found in an AC motor? fan assembly Armature brushes and commutator field windings
brushes and commutator
In a resistance start motor, current in the auxiliary winding always LEADS OR LAGS the current in the main winding.
Leads
Once the split-phase motor reaches [A] percent of its synchronous speed, the centrifugal switch [B] to [C] the________ windings.
75 to 80
opens
Disconnect
Auxiliary
The capacitor-start capacitor-run motor has how many capacitors?
2
In a synchronous motor, stator current will lead the applied voltage if the DC motor field is
over excited or under excited
overexcited
In actual practice, the _____ leads are interchanged to reverse the direction of a universal motor.
Armature
Micro stepping is achieved by__________
both answers
The maximum number of steps a stepper motor can make in a second is called ___________
stepping rate
The difference between the two classifications of PM motors is whether the rotor and field are made of permanent magnets or coils.
T F
True
In a variable reluctance motor, if the salient poles are 15° apart and the rotor poles are 20° apart, the step angle is ____ degrees.
5
In an AC Servo motor, the phase-shifted voltage is supplied to the ____ winding.
auxiliary
The stepper motor is typically used in a(n) ____ -loop system.
open
The speed of an AC Servo motor is changed by varying the voltage applied to ______
the auxiliary windings
The amount of force required to move the rotor of the BDCM away from the held position is called
holding torque
The speed of a wound armature PM motor is varied by changing the current applied to the
armature
The speed at which a stepper motor turns is increased by ______ applied to the stator.
Increasing the stepper rate
Find the cross product of vectors U and V such that U x V
U=0i+0j+1k
V= 0i+1j+0k
-1 0 0
The speed at which a stepper motor turns is increased by ______ applied to the stator.
Increasing the voltage
The Capacitor/resitance – start motor has the largest starting torque.
Capacitor
The difference between the setpoint in the feedback signal is referred to as the
_______ signal, and is produced by the _________
detector.
error
error
Which of the following influences causes a controlled variable to change?
the setpoint is adjusted
a load demand varies
A disturbance occurs
all three answers
all three answers
The controller can be considered the brain of a closed-loop system.
True
The _______ is sent to the final control element
control signal
The objective of _____ control is to prevent the controlled variable deviating from the setpoint.
feed-forward
The device that provides the muscle to perform the work in the closed loop system is referred to as the
actuator
When the load on a DC shunt motor is increased, its speed will________ and the amount of torque developed will _________
decrease, increase
Armature reaction is corrected by _________ , which is/are used to shift the neutral plane back to the proper position.
interpoles
The interpoles are always connected in parallel with the armature
False
When the motor speed increases, the CEMF in the Armature
increa/decreas
increase
How much power is needed when a torque is applied to a 413 lb mass that is moving 33 ft for 2 minutes. Do not include the unit designation ft-lb/min: example 3250
6815.0
AC motors that run at the same speed as the rotating magnetic field are called__________ motors.
synchronous
During operation, if the resistance of a wound – rotor motor is set to zero, it performs very much differently than a squirrel cage motor.
False
A(n) ____ in the external resistance of a wound – rotor motor causes an increase in the rotor resistance and therefore a reduction in the rotor current and speed.
increase
A Duty Rating of 20 on the nameplate of a motor indicates that it is designated to run continuously for 24 hours a day.
False
The A(amps) value on the nameplate for a three – phase motor indicates how much current will draw.
each phase
the entire motor
each phase
Calculate the percent slip of an induction motor that has a synchronous speed of 3600 RPM and a motors speed of 3330 RPM. Compute your answer to 2 decimal places and do not include the % symbol: example 4.03
actual-synch
////
synch
7.5
The CAP/RES – start motor is well suited for applications that require frequent starting loads, such as a refrigerator.
Capacitor
In a synchronous motor, stator current will lead the applied voltage if the DC motor field is
overexcited
Find the cross product of vectors U and V such that U x V
U=-2i+3j+4k
V= 3i+7j+2k
-22 4 4
A differential compound motor has __________ then a cumulative compound motor.
better constant speed
Which of the following conditions is compensated for by using the forward-control?
Excessive lag time
feedback signal
large disturbances
an error signal
Excessive lag time
large disturbances
List one example of a measurement device for motion control application and one example for process control application
motion control
process contro
Tachometer
thermometer
List two favorable features of synchronous motors.
power factor correction
constant speed
The speed of an AC motor depends on the
of the power supply and the
frequency
number of poles
What is the RPM speed of a single-phase 10-pole AC motor operating from a 60 Hz power source?
720.0
The speed of a universal motor can be controlled by________.
Tapping a field coil at various points
Either answer
Using a variable resistor
Either answer
The direction of the torque in a shaded – pole motor is towards the
Shaded pole
The amortisseur windings of a synchronous motor perform a similar function to the bars and shorting rings of a squirrel cage induction motor.
TRUE
If the stator’s magnetic field of the VR stepper motor moves clockwise, the rotor turns
counterclockwise
A stepper motor with twice the step angle of a second stepper motor will turn at _____ the RPM if the stepper rate applied to both is the same.
TWICE
The measured variable represents the condition of the controlled variable.
t f
True
To change the direction of the DC shunt motor with compensating windings, you must interchange leads ___ or ____.
F1 and F2
A1 and A2
In a DC series motor, if the Armature current is reduced to one half of its full load rating, the torque is ________
reduced
A(n) ___ field must be established in a split-phase motor to produce the starting torque.
rotating
When feedback and feedforward control are performed together, the primary function of the feedforward is to make corrections for ____disturbances, and feedback control is to make corrections for ________ disturbances.
measurable
unmeasurable
A DC shunt motor operating at 240 V draws 4.5 A. It has an output of 1 hp. Its efficiency is_____ %.
69
