Motor Controls Test 2

The addition of a control relay to a jogging circuit provides even greater control of the motor drive than the use of a jogging circuit alone.

true

Timing Relays can come equipped with timing contacts and instantaneous contacts.

true

Multiple push-button stations are used to control conveyor motors ____.

. on large shipping and receiving freight docks

How many wires are required for a two-wire control device?

2

If the available power is 208V-3 phase, and the control circuit is wired phase tophase, what is the control voltage? _____ volts.

208

Control systems that operate on ____ volts are often used in hazardous areas

24

Typical control voltages are 120 and ____ volts

24

If the available power is 480/277-3 phase, and the control circuit is wired fromphase to ground, what is the control voltage? _____ volts

277

List two (2) other names that are used in place of the term "schematic"

Elementary and Ladder

Timed contacts are either normally open or normally closed

true

When a motor must be started and stopped from more than one location, ____.

any number of start and stop buttons may be connected

Electronic Off-delay timers must have power applied ____ topermit the timing circuit to operate

at all times

A selector switch and the automatic pilot device can control a motor directly if their contacts are large enough to pass safely the full-load current of the motor. However, the contact capacity of these devices is usually not large enough for large motors.

true

A triac is used to connect the load to the line in a solid-state relay intended to control an AC load.

true

A two-wire control may be a toggle switch

true

Mechanically held relays are often used in machine tool control circuits.

true

In the case of a(n) ____, the thermal heaters open the overload contacts in the control circuit and de-energize the coil, thus stopping the motor.

overload

What are the applications for a motor-driven timer?

A process that has definite on and off b. A process that has a sequence of successive operations c. A process where infrequent starting of large motors is required d. All of them(Correct Answer) e. both a and b only

What does IEC stand for?

International Electrotechnical Commission

Select the definition of a wiring diagram. (Be thorough!!!)

Is a pictorial diagram. It shows the physical layout of all the equipment and allthe interconnecting wiring.

Why are contactors described as both control pilot devices and large magnetic switches controlled by pilot devices?

Large contactors may be controlled by relays. b. Because of the range in sizes available. c. All answers are correct.(Correct Answer) d. While large contactors can control heavy currents where overload protection is unnecessary or provided separately. e. Small contactors may be used as control devices for larger controls.

Electrical symbols usually conform to which standard?

NEMA

Are "ON" control stations used in multiple locations connected in series or parallel for latched-in contactors?

Only for parallel connections for "ON" not for "OFF"

Multiple start buttons are electrically wired in _________

Parallel

Select the definition of a schematic diagram. (Be thorough!!!

Shows the sequence of operation of equipment.

What will happen if the terminals of a blowout coil are reversed?

Theoretically, the motor action of the arc will be in the opposite direction.

What type of device is used to suppress voltage spikes in relay circuits?

Transient suppressor or Metal oxide varistor

The neutral wire can be_______.

White and Light Grey

The movable contact for a normally closed switch is drawn __.

above and touching the stationary contact.

The motor may be started or stopped from a number of separate stations by connecting all start buttons in parallel and ____ stop buttons in series.

all

Which of the following are factors to be considered when selecting a timing relay for a particular use. a. Allowable error b. Length of time delay required c. Timing range required d. Cycle of operation and reset time e. Cost f. Additional requirements (electrical rating, size, temperature)

all of them

What is the safety feature of a lock-stop push button?

both answers are correct

The larger contactor sizes are used to provide remote control of relatively high-current circuits where it is too expensive to run the power leads to the remote controlling location

true

The motor action established by the magnetic fields of the blowout coil and the arc plus the use of arc deflectors or arcing horns cause the arc to Lengthen and move upward.

true

The principal difference between a contactor and a motor starter it that a motor starter contains overload relays and a contactor does not.

true

Three-wire control prevents the restarting of machinery when power is restored.

true

When a jogging circuit is used, the starter can be energized only as long as the jog button is depressed

true

Schematics show components in their electrical sequence without regard for __.

physical location

Starters, contactors, and ____ are similar in construction and operation

relays

The use of a selector switch in the control circuit to obtain jogging requires a three-element control station with start and stop controls and a ____ switch.

selector switch

Multiple stop buttons are electrically wired in _________

series

Single-pole and double-pole switch symbols are shown as.

single break. b. double break c. all of the above(Correct Answer) d. NO and NC

When there are several timers that meet the requirements of a given application, it is advisable to select the timer with the ____.

smallest number of operating parts

Jogging can be implemented using a ____, two-position selector switch

standard-duty

Mechanical connections are shown with ___.

straight broken lines

The symbol for a __ switch represents a bimetal helix.

temperature

24 volts is the most common control voltage used in an intrinsically safe system

true

A circle is most often used to represent a coil in a motor control schematic, because the letters and/or numbers are written in the circle to identify the coil.

true

Another name for a schematic diagram is an elementary diagram

true

Control magnetic relays are used to controlsmall loads

true

Control relays are small magnetic switches used on simple branch circuits to control complex wiring system operations.

true

Electronic timers have become increasinglypopular in industrial applications.

true

Intrinsically safe systems cannot supply enough energy to ignite the atmosphere in a hazardous location

true

Is the pneumatic timer the most commonly used in industrial applications?

true

It is desirable to extinguish the arc as quickly as possible to keep the contacts cool and this prolong contact life

true

Ladder diagrams are sometimes referred to as elementary diagrams

true

Main or subassembly line conveyors use sequence control.

true

When components are used to perform the function of stop, they are generally wired ____ with the motor starter coil.

n​ormally closed and connected in series

If set in the ____ position, the coil is connected directly to the power line and the motor will run continuously.

on

If the HOA switch is set in the off position, ____ current can flow to the coil of the starter.

on

When the switch is set in the hand position, contacts 1 and 2 are closed, and contacts 3 and 4 are ____.

open

The operation of the overload protection ____ the control circuit.

opens

An HOA switch is a two position selector switch

false

An electrician in the field must connect a circuit using a line diagram.

false

In a three-wire control circuit, when the supply voltage returns after a failure, the circuit is re-energized.

false

It is sometimes desirable to operate push buttons or other control devices at some voltage higher than the motor voltage

false

Magnetic relays are affected by the electricnoise and the voltage spikes induced in the system

false

Neither jogging nor inching prevent a holding circuit.

false

Start buttons are electrically wired in series.

false

The greatest advantage of relays with mechanicalcontacts is that they are resistant to shock and vibration

false

The operation of each additional push-button control station is different from that of the single push-button control in the basic three-wire circuit.

false

The term inching is often used when referring to across-the-line starters.

false

The equipment ground can be _______.

green and bare

What conductor can be any color except white, light gray, green or bare?

hot

A three-wire control circuit uses momentary contact, start-stop stations, and a holding circuit interlock connected ____ with the start button to maintain the circuit

in parallel

It is necessary to restart a motor after it has been stopped by a three-wire control circuit with ____ protection

low voltage

A flow switch is classified as a pilot device.

true

A control relay is an electrically operated switch.

true

Why will the blowout coil also operate on AC

Since the current reverses simultaneously in the blowout coil and arc, the motor action (arc deflection) occurs in the same direction.

Which of the following factors will affect the selection of a timing relay. a. Type of power supply b. contact ratings c. timer contact arrangement d. temperature range e. dimensions

all of them

Sequence control is required whenever the ____ must be operating before the machine itself can be operated safely.

auxiliary equipment associated with a machine

Jogging is defined by ____ as "the quickly repeated closure of a circuit to start a motor from rest for the purpose of accomplishing small movements of the driven machine."

nema

A hand-off automatic switch may be a stand alone control or incorporated into a start-stop push button station.

true

A pneumatic timer is adjusted by positioning a needle valve to vary the degree of orifice restriction.

true

A power transistor is used to connect the load to the line in a solid-state relay intended to control a DC load.

true

A selector push button can be used to obtain jogging

true

An advantage of using a two-wire control device is because automatic controls may be used to control a motor or an operation without requiring the presence of an operator.

true

Motors draw half as much current on high voltages as they do on low voltages

true

Pilot lights are tested frequently to ensure operation

true

Pilot lights are used for safety and communication.

true

Pneumatic timers have good repeat accuracy.

true

Pressing any stop button de-energizes the coil.

true

Relays are used more often to open and closecontrol circuits than to operate power circuits.

true

Schematics are always drawn to show components in their de-energized or off state

true

Sequence control exists when starters are connected so that one cannot be started until the other is energized

true

The conventional three-wire, push-button control circuit may be extended by the addition of one or more push-button control stations.

true

Timing relays are used for any application wherethe operating sequence requires a delay

true

When the load side of the circuit is separated from the control side by a light beam it is called optoisolation

true

You should never wire in a set of normally closed contacts in a series with thecoil of the same device.

true

The selector switch is controlled by ____ the push button sleeve.

turning