Motor Control 3: Lesson 5 - Variable Frequency Drives Flashcards
Speed and ______ are two physical quantities that must be controlled in a motor drive.
a. direction
b. temperature
c. torque
c. torque
Motor control systems that control motor speed without feedback data for torque or speed are called ______ control systems.
a. closed-loop
b. open-loop
b. open-loop
Lower initial cost and easier installation are two advantages of a(n) _______ motor control system.
a. closed-loop
b. open-loop
b. open-loop
The VFD controls the speed of an AC motor by varying the ______ to the motor.
a. current
b. frequency
c. voltage
frequency
A tachometer/generator produces a feedback voltage which is directly proportional to the ______ of the motor.
a. horsepower
b. speed
c. torque
speed
A motor control system that uses a tachometer to control the speed of the motor is called a(n) ______ system.
a. closed-loop
b. open-loop
closed-loop
Drive, comparator, sensor, and amplifier are the four parts of a(n) ______ system.
a. closed-loop
b. open-loop
closed-loop
Tachometer/generators and optical encoders are two types of devices that are generally used to provide speed reference signals in a(n) ______ speed control system.
a. closed-loop
b. open-loop
closed-loop
In a closed-loop speed control system, the ______ is the desired speed selected for the motor connected to the drive.
a. feedback speed value
b. feedback summing amplifier
c. set point speed value
set point speed value
What is the term used to identify the speed change in Segment 1?
a. Constant speed
b. Speed ramp-down
c. Speed ramp-up
speed ramp-up
What is the speed in Segment 2?
a. Constant speed
b. Speed ramp-down
c. Speed ramp-up
constant speed
What is the term used to identify the speed change in Segment 3?
a. Constant speed
b. Speed ramp-down
c. Speed ramp-up
speed ramp-down
When using a VFD, a motor’s ramp-up speed can be adjusted to vary from a few seconds to more than ______.
a. 60 seconds
b. 120 seconds
c. 180 seconds
120 seconds
Which type of motor is generally less expensive and requires less maintenance?
a. AC
b. DC
AC
______ are installed on power lines feeding VFDs to lessen the effects of harmonics generated by the VFDs.
a. Line reactors
b. Load reactors
Line reactors
What DC control voltage is used to control the speed of the motor connected to the VFD?
a. 5 VDC
b. 10 VDC
c. 24 VAC
10 VDC
If a worker was connecting a normally open discrete contact to the terminal block for the VFD and needed to turn the motor on and run the motor in the forward direction, to which two terminals would the worker connect the contact?
a. 02COM / 020
b. 10COM / 100
c. ACOM / A101
10COM / 100
When connecting an alarm light or audible alarm to the “02” (02COM, 02C, or 020) terminals of the VFD, the alarm would be ? powered.
a. externally
b. internally
externally
What type of connector is required to connect the communications cable when connecting an external personal computer to the VFD to monitor or program the device?
a. HDMI
b. RJ-11
c. RS232
RJ-11
The VFD is an example of a(n) ______ control.
a. closed-loop
b. open-loop
b. open-loop
How many factory default speeds are available for this VFD?
a. 2
b. 3
c. 4
3
Where would the device be connected if the VFD could be converted for use in a closed-loop system by connecting an appropriate analog device that produced a 0-10 VDC output to the VFD?
a. 02COM / 020
b. 10COM / 100
c. ACOM / A101
ACOM / A101
The motor, connected to the VFD, can be run in the reverse direction.
True or False
True
When considering the environmental concerns of VFD installations, factory enclosures should have a(n) ______ rating appropriate to the level of protection for the installation.
a. IEC
b. NEMA
c. NFPA
NEMA
The equipment manual and labels on the VFD equipment are two sources of information that should be consulted before installing a VFD.
True or False
True
The ______ of a VFD establish(es) the speed, rotation direction, and stopping parameters for the motor.
a. control set points
b. factory preset parameters
c. incoming power source
control set points
All VFDs are configured and programmed the same way.
True or False
False
A drive-mounted programming interface, handheld programmer, external laptop computer, or other computers on a data network can be used as programming devices to configure VFDs.
True or False
True
Which programming software feature monitors and displays the value of all drive and motor parameters in real time?
a. Display drive status
b. Error messages and alarms
c. Parameter updates
Display drive status
Match the load characteristics that the VFD is required to deliver to each type of load.
Fans, centrifugal blowers, and centrifugal pumps -
Hoists, conveyors, mixers, and reciprocating or rotary compressors -
Wheel grinders, large driller machines, lathes, planers, and boring machines -
Choices:
- Constant Torque Loads
- Variable Torque Loads
- Constant Horsepower Loads
Fans - Variables
Hoists - Constant Torque
Wheel Grinders - Horsepower
Which drive programming software feature displays drive parameters, such as voltage, current, frequency, speed, and power consumed?
a. Display drive status
b. Error messages and alarms
c. Parameter updates
Parameter updates
Re-torquing is a good procedure to use to check the status of terminals that are held in place with bolts or screws.
True or False
False
To begin troubleshooting a VFD, four sections of a drive circuit must be inspected: input devices, output devices, programming configuration, and VFD internal components.
True or False
True
Most ______ problems are identified and corrected during startup.
a. input device
b. programming
c. VFD internal component
programming
The three basic categories of tasks necessary to maintain a VFD in proper operating condition are: keep it clean, keep it dry, and keep connection tight.
True or False
True
