Motor Control, Level III - Lesson 1, 2, 3, 4, 5, 6, 7, 8, 9

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What is the temperature range that a Type J thermocouple can sense in a process?

-190°C to +800°C

When using a VFD, a motor's ramp-up speed can be adjusted to vary from a few seconds to more than ? .

120 seconds

Opto-isolators used for AC signals have ? LED(s) in the opto-isolator and DC circuits have ? LED(s) in the opto-isolator.

2 / 1

The standard coil voltage ratings for DC contactors are 12, 24, 48, 120, and ? .

240 V DC

How many DC motor wiring configurations are there?

3

A thermistor is used to measure temperature in a process. The circuit includes an indicator that shows the temperature to be 88°C. Convert the Celsius temperature to its equivalent Fahrenheit value.

32+(88 x 1.8) = 190.4F The correct answer is: 190.4°F

0-10 VDC, 4-20 ma, and 3-15 psi are examples of what type of signal?

Analog

? signals provide a continuous indication of the value or position of the variable or entity being monitored.

Analog

What type of signal is continuous, varying from a minimum to a maximum value?

Analog

What is the speed in Segment 2?

Constant speed

Which section of solid-state DC drives is capable of varying the motor speed above and below the motor base speed?

Control section

What type of flow meter depends upon the twist of the tube containing the flowing fluid to sense flow rate? Select one:

Coriolis

When analog control devices are located large distances from each other, which type of signal is preferable for installing the control wiring?

Current

Using the input module and sensor schematic diagram shown, the output of the sensor field device is ? .

Current sinking

Using the input module and sensor schematic diagram shown, the output of the sensor field device is ? .

Current sourcing

The ? motor can be started manually with a rheostat.

DC

Dynamic braking is a motor braking technique where the motor is operated as a ? after the main power is removed.

DC generator

Which type of pressure sensor replaces atmospheric pressure as a reference pressure with a second process pressure?

Differential pressure

What type of signal has only two states: ON and OFF?

Discrete

Proportional control valves are always controlled with an electronic voltage or current signal. (T/F)

False

Thermocouple transmitters generally produce 0-15 mA output signals. (T/F)

False

Iron and constantan thermocouple wire are required for ? -type thermocouples.

J

? potentiometer position sensors sense the linear motion or position of some object or process that moves in a straight line. As the object moves, the shaft of the potentiometer attached to the object moves, changing the position of the potentiometer.

Linear

If an analog circuit with a 4-20 mA DC-current-based analog signal is reading 12 mA and a 1-5 VDC relay is connected to the circuit with a 250 ohm resistor in parallel with the input terminals, what would be the relay input voltage?

Note: .012 (I) x 250 (R) = 3 VDC signal The correct answer is: 3 V DC

A certain process control system utilizes a tank that is 10 feet tall. The transducer that measures the level of liquid in the tank is located 2 feet from the bottom of the tank. If a 1-5 VDC signal is used to monitor the top 8 feet of water in the tank, how much water is in the tank when the analog value read at the transducer is 3.5 VDC?

Note: A 4 volt signal (5 V - 1 V) represents 8 feet of water in the tank. 4 V/8 feet = 0.5 volts per foot. 3.5 volts represents 3.5 V - 1 V = 2.5 volts of signal. 2.5 V/0.5 V = 5 feet of water. Since the transducer is only monitoring the top 8 feet of water in the tank, the height of water in the tank is 2 feet (not monitored) + 5 feet (the measured value) = 7 feet. There are 7 feet of water in the tank.

Which section of solid-state DC drives supplies the DC voltage to the motor?

Power section

? are analog output devices that document industrial and commercial process data .

Recorders

Which braking method decelerates the motor faster than the other?

Regenerative braking

? potentiometers position sensors detect the angular or rotational position of a shaft. As the shaft rotates, the position of the potentiometer shaft rotates as well, and the resistance output of the sensor changes to indicate that shaft's position.

Rotary

The ? trigger produces a deadband, so the output does not switch ON and OFF as the input moves above and below the trigger point.

Schmidt

What type of device has one type of analog signal as an input, and produces another type of analog signal as an output?

Signal converter

What is the term used to identify the speed change in Segment 3?

Speed ramp-down

What is the term used to identify the speed change in Segment 1?

Speed ramp-up

A 1-5 VDC analog device can be used in a 4-20 mA DC loop circuit if a 250 ohm resistor is connected across the input to the device and the 4-20 mA DC current is routed through the resistor. The current signal produces the proper voltage to operate the 1-5 VDC device. (T/F)

True

A smart or intelligent device contains a solid-state circuit or chip that provides communication and diagnostic capabilities for the device. (T/F)

True

Control of the armature or field voltage is used to control the speed. (T/F)

True

Controller input and output modules have opto-isolation between the field device power and the controller or motor drive system power to eliminate noise and operational problems. (T/F)

True

Discrete control valves are either open or closed. Since these valves have only two states, they do not require analog input signals and operate simply by applying the appropriate voltage to the coil of the valve. (T/F)

True

Efficient troubleshooting of a network control system requires knowledge of the vendor's system software program. (T/F)

True

It is important that proper precautions and handling procedures be understood and followed in order to avoid ESD damage to solid-state devices. (T/F)

True

It is important to make and break contacts as quickly as possible to extinguish the arc promptly and to extend the life of the contacts and contactor. (T/F)

True

Most DC motor drives detect and display common circuit and/or fault numbers to help identify problem conditions. (T/F)

True

Proportional control valves respond to an analog signal and adjust flow over a range of 0% to 100% of the capacity of the valve. The rate of flow in these valves is proportional to the analog signal applied to the valve. (T/F)

True

The self-diagnostic capabilities of smart devices are helpful when troubleshooting smart systems. (T/F)

True

To check if a rheostat is working properly, test each tap for a different resistor value using a DMM. (T/F)

True

When considering response time to a change in stator temperature in a motor, thermocouples are faster than RTDs and would provide a quicker response than an RTD. (T/F)

True

When performing maintenance with the motor off, a visual inspection should include a check for excess dirt accumulation, burns, or damaged starter components. (T/F)

True

When stopping heavy loads without a brake, the large inertia of the load continues to rotate the motor after the ramp down voltage has stopped. (T/F)

True

When the core of a linear variable differential transformer (LVDT) is in the center or null position, the voltages in the two secondary transformers are equal. Since these transformers are connected to oppose each other, the resulting output voltage is zero since the voltages cancel each other out. (T/F)

True

What type of flow meter requires that particles must be present in the fluid being monitored to reflect signals back to the flow sensor?

Ultrasonic

DC currents stay ? the zero axis and maintain a constant current flow to the motor.

above

A(n) ? signal can be used to control the speed of a motor, determine the position of a valve, or indicate the level of a tank at every level as the tank fills or empties.

analog

Transducers convert a variable such as temperature, position, flow, or pressure into a(an) ? signal that is used by the control system.

analog

The braking resistor is connected to the ? during dynamic breaking.

armature leads

The magnetic ? coil produces a magnetic field between the breaking contacts that forces the arc up, increasing the length of the arc and causing it to dissipate faster.

blowout

A ? pressure sensor often uses an LVDT to sense position relative to the pressure applied to the sensor.

bourdon tube

A motor control system that uses a tachometer to control the speed of the motor is called a(n) ? system.

closed-loop

Drive, comparator, sensor, and amplifier are the four parts of a(n) ? system.

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.

closed-loop

The ? section of a DC drive is also capable of controlling the motor direction.

control

Generally, ? signals with a very low source resistance are less sensitive to electrical noise from welders and electric motor starters.

current

A limit switch is an example of a(n) ? signal.

discrete

Most new or upgraded DC systems use what type of starting method?

electronic DC drive

A(an) ? event is the rapid flow of electrons between two bodies of unequal charge.

electrostatic discharge

Turbines and paddlewheels are often immersed directly in a process liquid and are used to measure ? .

flow

The VFD controls the speed of an AC motor by varying the ? to the motor.

frequency

Arc chutes typically absorb ? than 80% of the energy released during the interruption of current flow as the contacts open.

greater

When starting a DC motor with a rheostat, the current at the field winding is ? and the current at the armature is ? .

high / low

During the operation of a DC rheostat motor starter, the resistance is ? in the field winding and ? in the armature until the motor is brought up to full speed.

increased / reduced

AC/DC, DC current-sinking, DC current-sourcing, and transistor-to-transistor logic (TTL) are the four most common types of ? circuits used in controller input modules.

input

The voltage level of a class 1 solid-state device that may cause potential damage is ? .

less than 1,000 V

A common type of pressure sensor used to measure weight is the ? sensor.

load cell

Constant temperature and calorimetric sensors are types of ? flow sensors.

mass

Thermocouples are temperature-sensing devices that produce a ? when the temperature increases.

millivolt level voltage

Most DC motor contactors consist of ? set(s) of contacts.

one

Lower initial cost and easier installation are two advantages of a(n) ? motor control system.

open-loop

Motor control systems that control motor speed without feedback data for torque or speed are called ? control systems.

open-loop

AC, DC, and transistor-to-transistor logic (TTL) are the three most common types of output circuits used in controller ? modules.

output

Analog devices connected using a voltage type analog signal are connected in ? with each other.

parallel

Regenerative braking returns the regenerated power of a DC motor back to the ? .

power source

DC drives use a ? method to smoothly accelerate and decelerate the motor.

ramping

RTDs and thermistors are temperature sensing devices that exhibit a change in ? , which is dependent upon the temperature of the device.

resistance

Because solid-state drives do not use ? , energy is not wasted in the form of heat.

resistors

A linear variable differential transformer has three windings. The primary winding is connected to an AC voltage. The secondary windings are connected in ? , and the output from these windings represents the position of the process being monitored.

series

Analog devices connected using a current loop analog signal are connected in ? with each other.

series

When two or more thermocouples are connected in ? to increase the output voltage from the sensor, the connection is referred to as a thermopile.

series

In a closed-loop speed control system, the ? is the desired speed selected for the motor connected to the drive.

set point speed value

A(n) ? converts from one analog signal range to a different analog signal range when the analog signal values do not match.

signal conditioner

Sensors that use an NPN transistor to switch the output circuit are current- ? devices.

sinking

Motor driven proportional control valves are generally ? to operate than pneumatic control valves.

slower

Ramping works well for ? loads.

small

Sensors that use a PNP transistor to switch the output circuit are current- ? devices.

sourcing

A tachometer/generator produces a feedback voltage which is directly proportional to the ? of the motor.

speed

Tachometer and encoder are two devices that are used to monitor the ? of the motor.

speed

Resistance temperature detectors (RTDs) and thermocouples are typical of analog sensing devices that measure ? in a process.

temperature

Speed and ? are two physical quantities that must be controlled in a motor drive.

torque

A ? is a device that receives one type of energy and converts it to another type of energy and generally includes a sensor and a transmitter.

transducer

A(n) ? flow sensor uses an object called a bluff body, which is placed in the fluid flow to produce whirlpools or eddies in the fluid flow stream.

vortex

Which type of analog signal can be used to not only control the speed of a motor, but also the direction of rotation of the motor?

±5 VDC


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