Electrical Motor Controls, Chapters 21-30 Tech-Cheks

Even at full conduction, an SSR presents some residual resistance, which can create a voltage drop of up to approximately _____ V in the load circuit.

1.5

A voltage-output pressure sensor typically outputs 0 VDC to _____ VDC proportional to the rating of the pressure sensor.

10

A current-output pressure sensor typically outputs 4 mA to _____ mA proportional to the rating of the pressure sensor.

20

The high-frequency sound waves of an ultrasonic sensor are typically in the _____ kHz range.

200

Cold resistance is measured at _____ °C

25

_____ drives are the most common drives because they can easily vary the speed of a 3 phase motor.

AC

_____ sensors can detect materials such as plastic, glass, water, moist wood, etc.

Capacitive

Pressure sensors are suited for a wide variety of pressure measurements on _____, pumps, and other similar equipment.

Compressors

_____ current glow is the movement of electrons from positive to negative.

Conventional

The _____ flowing through a photodiode increases as the resistance decreases.

Current

_____ is one of the most suitable industrial applications of SCRs.

DC motor control

_____ mode is a method of ultrasonic sensor operation in which the emitter and receiver are placed opposite each other so that the sound waves from the emitter are received by the receiver.

Direct

The operation of a thermistor is based on the _____ -hole theory.

Electron

_____ is a ratio of the amplitude of an output signal to the amplitude of an input signal.

Gain

_____ is a phenomenon that occurs when a relay fails to turn off because the current and voltage in the circuit reach zero at different times.

Half-waving

A(n) _____ sensor detects the proximity of a magnetic field.

Hall effect

_____ actuation is an active method of Hall effect sensor activation in which a magnet is oriented perpendicular to the surface of the sensor and is usually centered over the point of maximum sensitivity.

Head-on

_____ trip is the trio point after the overloads have tripped and have been reset (motor operating near or over nameplate rated current).

Hot

_____ and contamination are the primary causes of photocell failure.

Humidity

_____ heated thermistors are used for precision temperature measurement and temperature compensation.

Indirectly

The primary difference between a photodiode and a regular diode is that a photodiode has an addition of a _____ in it's housing for focusing light on the PN junction.

Lens

A photoconductive cell (photocell) is a device that conducts current when energized by _____

Light

_____ current is the amount of current drawn by a load when energized.

Load

With a(n) _____ thermistor, an increase in temperature causes the resistance of the thermistor to decrease.

NTC

_____ error is a slight mismatch between internal components.

Offset

_____ control is the control of the time relationship between two events when dealing with voltage and current.

Phase

Without light, the _____ of the photodiode is high.

Resistance

A photocell is, in effect, a variable _____

Resistor

_____ scan is a method of scanning in which the transmitter and receiver are housed in the same enclosure and the transmitted light beam is reflected back to the receiver from the reflector.

Retroflective

_____ start is the most common solid-state starting method.

Soft

_____ stop is the most common solid-state motor starter stopping method.

Soft

_____ scan distinguishes between shiny and nonshiny (matte) surfaces.

Specular

A thermistor is a(n) _____ -sensitive resistor.

Temperature

_____ is the largest problem in applications that use an SSR.

Temperature rise

A flow detection sensor operates on the principle of _____ conductivity.

Thermal

A(n) _____ switching relay has a built-in synchronizing circuit that controls the amount of output voltage as a function of the input voltage.

analog

An op amp is often used in digital circuits that require the _____ amplification of a weak signal.

analog

Hall voltage varies depending on how close the magnet is to the Hall generator, which acts as a(n) _____ signal.

analog

The _____ starting method provides the highest possible starting torque per ampere of line current and is the most effective means of motor starting for applications where the inrush current must be reduced with a minimum sacrifice or starting torque.

autotransformer

The N-type material in a unijunction transistor functions as the _____ and has two leads.

base

In a two-lead phototransistor, the _____ is replaced by a clear covering that allows light to fall on the base region.

base lead

In any transistor circuit, the _____ junction must always be forward biased.

base/emitter

A _____ device is a device in which both holes and electrons are used as internal carriers for maintaining current flow.

bipolar

A gate current is used to reduce the level of _____ voltage necessary for an SCR to conduct or fire.

breakover

Amplifiers connected together are called _____ amplifiers.

cascaded

The _____ method is a method of SSR replacement in which a logical sequence is used to determine the reason for a failure.

circuit analysis

The _____ is the first layer of protection for the glass or plastic core of an optical fiber cable.

cladding

A(n) _____ system may have automatic correction control.

closed-loop

An SSR circuit consists of an input circuit, a _____ circuit, and an output circuit.

control

It is possible for small amounts of _____ (OFF-state leakage) to pass through an SSR because some conductance is still possible even though the SSR is turned off.

current

The _____ region is the point at which the transistor is turned off and no current flows.

cutoff

As electrons move across the _____ of a light-emitting diode (LED), they give up extra kinetic energy, which is converted to light.

depletion region

Generally, any material with a _____ constant greater than 1.2 may be detected.

dialectric

An optocoupler uses a glass _____ sandwich to separate input from output.

dielectric

The _____ provides wide bandwidth and high impedance in an op amp.

differential amplifier

When transistors are used as switches, a _____ can be mounted across the transistor to prevent damage from high-voltage spikes (transients).

diode

The best scanning method for height and distance monitoring is _____ scan with modulated controls.

direct

The input circuit is deactivated when a voltage less than the specified minimum _____ voltage of the relay is applied.

dropout

Inductive proximity sensors operate on the _____ principle.

eddy current killed oscillator

The _____ light beam is the area of light that travels directly from the transmitter to the receiver.

effective

Communication is the transmission of information from one point to another by means of _____ waves.

electromagnetic

A proximity sensor (proximity switch) is a solid-state sensor that detects the presence of an object by means of a(n) _____ sensing field.

electronic

The input of a common-_____ circuit is across the base and emitter, while the load is across the collector and emitter.

emitter

Since a(n) _____ MOSFET does not conduct at zero gate voltage, it is often called a normally off MOSFET.

enhancement

The main body of a(n) _____ MOSFET is composed of a highly resistive P-type material.

enhancement

An RC circuit is a circuit in which resistance (R) and capacitance (C) are used to help _____ the power in a circuit.

filter

A(n) _____ serves as the control point for an SCR.

gate

The two sections of P-type material constitute the _____ of a JFET.

gate

Problems with IGBTs and other solid-state switches can be reduced by keeping their _____ clean for proper airflow movement.

heat sinks

Triacs cannot replace SCRs in _____ applications.

high-current

JFET's are used extensively in circuits where low power and high _____ are factors.

impedance

A(n) _____ proximity sensor is a sensor that detects only conductive substances.

inductive

The "PIN" in PIN photodiode stands for P-type material, _____, and N-type material.

insulator

The _____ resistance measurments taken when troubleshooting IGBT's are used to determine whether the resistance is too low and the device is defective.

leakage

Hall effect sensors are also used to replace mechanical _____ switches in applications that require the detection of an object's position.

limit

In a(n) _____ light source, the light source is turned on and off at a very high frequency, normally several kilohertz (kHz).

modulated

A solid-state motor starter is an electronically operated switch (contactor) that uses solid-state components to eliminate mechanical contacts and includes _____.

motor overload protection

Because there is a small delay (usually less than 30 sec) before a flow detection sensor heats enough to signal no flow, the sensor acts like a _____, which allows for a short time delay to pass before signaling a problem.

motor starter overload

A diac has _____ resistance because it does not conduct current until the voltage across it reaches breakover voltage.

negative

A(n) _____ is needed to properly test an SCR under operating conditions.

oscilloscope

In darkness, a phototriac is not triggered. The remaining leakage current is referred to as _____ current.

peak blocking

A fiber optic receiver normally contains a(n) _____ that converts light back into electrical signals.

photodiode

Typical Hall effect sensor package configurations include cylinder, proximity, vane, and ____.

plunger

One disadvantage of an IGBT is that the switching speed is inferior to that of a(n) _____ MOSFET.

power

One of the significant advantages of an SSR over an EMR is its _____.

response time

An important feature of triacs is the absence of a(n) _____ condition of high voltages and high current, such as those found in diodes and SCRs.

reverse breakdown

As long as the emitter voltage remains less than the internal voltage, the emitter junction will remain _____, even at a very high voltage.

reverse-biased

Triacs are the equivalent of two SCRs connected in a _____ arrangement with gates also connected to each other.

reverse-parallel

Materials such as foam, fabric, and _____ are difficult for ultrasonic sensors to detect and are better detected by photoelectric or proximity sensors.

rubber

A flow detection sensor is a sensor that detects the movement (flow) of liquid or gas using a(n) _____.

solid-state device

A typical solid-state _____ circuit consists of both start and run contractors connected in the circuit.

starting

Triacs, diacs, UJTs, and SCRs operate only as _____.

switches

Photoelectric sensors that switch DC circuits normally use _____ as the switching element.

transistors

A UJT is typically used as a triggering circuit for a _____ or similar device.

triac

Diacs are used almost exclusively as _____ devices.

triggering

A JFET is a(n) _____ device.

unipolar

The main difference in operation between a JFET and MOSFET is that _____ is applied between the gate and the P and N regions of the MOSFET structure.

voltage

A _____ is a noninverting amplifier.

voltage follower

Electrically, a diac operates in a manner similar to two _____ that are connected in series in opposite directions.

zener diodes

The _____ switching relay is the most widely used relay.

zero