Motor Controls 1 ch.s 1-12

How can the direction of rotation of any three phase motors be reversed?: Answer in your own words.

By changing any two stator leads

Fuses and circuit breakers are generally employed for ____ protection.

Circuit

A control relay is used to provide jogging in one direction only.

False

Auxiliary contacts are intended to control large amounts of current.

False

High voltage surges are harmless and cannot damage electronic components connected to the power line.

False

In schematics, electrical components are always shown in their energized or on state.

False

Integral horsepower manual starters with low voltage release will restart automatically after a power failure without being reset.

False

Magnetic control systems generally operate on 240 volts.

False

Magnetic type overload relays are sensitive to ambient temperatures

False

Most control transformers are made with one primary winding and two secondary windings.

False

Most reversing controllers only contain mechanical interlocks.

False

Motor starters are basically a contactor and overload relay mounted together. Most do not need auxiliary contacts.

False

Normally open switches are drawn with the movable contact above and touching the stationary contact.

False

Pneumatic timers are affected by variations in ambient temperature or atmospheric pressure.

False

Schematic or ladder diagrams are read from right to left and from bottom to top.

False

Starters that are intended to protect motors that operate on 240 volts should contain 4 load contacts.

False

The double acting push button has two terminal screws.

False

The on-delay relay is often referred to as DODO.

False

The symbol for a limit switch illustrates a ball float.

False

Thermal overload relays trip faster when located in a cool area than in a warm area.

False

When M coil energizes, only the first M contact changes position.

False

With automatic control, an operator does not have to initiate certain actions.

False

____ -automatic switches are generally used to select the function of the motor controller either manually or automatically.

Hand-Off

What would happen if both contactors were energized at the same time? Answer in your own words.

If there were no other safety measures taken place, both motors would start at the same time.

How is an additional stop button added into a circuit.

It is added in series with the existing stop button.

In schematics, what do dashed lines between components indicate?: Answer in your own words.

Those components are mechanically connected/ one component.

What is the function of a holding (sealing) contact?: Answer in your own words.

To allow current to constantly flow through the circuit without the need for someone to standby to continue to press the start button.

Any heat source can cause an overload to trip.

True

Control transformers generally have screw terminals connected to the primary and secondary leads.

True

Diodes are used to suppress the voltage spikes produced by coils that operate on direct current.

True

Hysteresis loss is often referred to as molecular friction.

True

If R coil energizes, all R contacts change position.

True

In a schematic, any contact that is marked with the same letter or number as a coil is controlled by that coil regardless of where it is located in the schematic.

True

Instantaneous contacts change their positions immediately when the coil is energized and change back to their normal positions immediately when the coil is de-energized.

True

Manual control may be accomplished by simply connecting a switch in series with the motor.

True

Manual push button line voltage starters are manufactured with two or three line voltage contacts.

True

Many bimetal strip type overload relays can be set for either manual or automatic reset.

True

Many industries prefer to ground the control system and it is a very common practice.

True

One common uses for the normally open set of contacts on an overload relay is to provide an input signal to a programmable logic controller (PLC).

True

One of the main considerations when installing a machine is the power source.

True

Overload relays are designed to open the circuit when the current becomes 115 percent to 125 percent of the motor full load current.

True

Pneumatic timers are adjustable over a wide range of time periods.

True

Protection can be placed on the primary or secondary side of the control transformer.

True

Some motors can draw up to 600 percent of rated full load current during starting.

True

The START-STOP push button circuit is the basis for many other control circuits.

True

The advantage of mercury relays is that each time the relay is used to contact is renewed, eliminating burning and pitting caused by an arc when connection is made or broken.

True

The flow switch symbol is used for both liquid and air flow switches.

True

The movable contact of the normally open held closed switch is drawn below the stationary contact.

True

There may be times when it is desirable to have more than one START-STOP push button station to control a motor.

True

Vacuum contactors enclose their load contacts in a sealed vacuum chamber.

True

You can obtain jogging control with the use of a selector switch.

True

a selector switch is used to break the connection to the holding contacts.

True

Insurance companies established the ____ organization in an effort to reduce the number of fires caused by electrical equipment.

UL

What happens to the three load contacts connected between the three phase power line and the motor after one of two start buttons are pressed?

When either start button is pressed, all M contacts will close and the motor will start.

Electrical interlocking can be accomplished by connecting the normally closed ________ contacts on one contactor in series with the coil of the other contactor.

auxiliary

Some common causes of motor overloads are bad ____ in either the motor or the load motor operates.

bearings

The most common coil symbol used in schematic diagrams is the ____.

circle.

Control transformers are generally protected by fuses or ____.

circuit breakers

Fuses and ____ are designed to protect the circuit from a direct ground or short-circuit condition.

circuit breakers

When a component is used to perform the function of stop in a control circuit, it will generally be a normally _______ component.

closed

Timer relays are similar to other control relays in that they use a(n) _________ to control the operation of some number of contacts.

coil

Inching control requires the use of a separate _______ because the power supplied to the motor must be separate from full line voltage.

contactor

If any one of the overloads should trip, a mechanical mechanism opens the load ____ and disconnects the motor from the line.

contacts

Magnetic overload relays can be divided into two major types: electronic and ____.

dashpot

Fuses which are intended to provide both short circuit protection and overload protection are called ____ time delay fuses.

dual element

The continuous change of both amplitude and polarity of the magnetic field causes currents to be induced into the metal core material; these currents are called ____ currents.

eddy

When one side of the control transformer is not grounded, it is generally referred to as a(n) ____ system.

floating

What does interlocking do?Answer in your own words.

forces one contactor to be de-energized before the other one can be energized.

Motors of 1 horsepower or less are considered ____ horsepower.

fractional

High impedance voltmeters can indicate some amount of voltage caused by the capacitance of the ground and induced voltage produced by surrounding magnetic fields. These are generally referred to as ____ voltages.

ghost

When one side of the secondary winding of a control transformer is grounded, the control system is referred to as a(n) ____ system.

grounded

________ forces one contactor to be de-energized before the other one can be energized.

interlocking

What is the difference between jogging and inching?

jogging uses full line voltage while, inching uses about half of the full line voltage.

Mechanically held contactors and relays are often referred to as ___ contactors or relays.

latching

The current flow through the MOV is called ____ current and is so small that it does not affect the operation of the circuit.

leakage

____ switches are drawn by adding a wedge to one of the four basic switches.

limit

Contactors are equipped with contacts intended to connect high current loads to the power line; these large contact are called ____ contacts.

load

Motor starting current is referred to as ____ current.

locked rotor

In a diagram, dashed lines drawn between two or more components indicates that they are ________ connected.

mechanically

In a three-wire start/stop motor control circuit, the Stop Button can be wired normally open or normally closed. For the circuit to operate properly, the Stop Button should be wired _______.

normally closed

In a three-wire start/stop motor control circuit, the Start Button can be wired normally open or normally closed. For the circuit to operate properly, the Start Button should be wired _______.

normally open

To simplify the task of converting the schematic diagram into a wiring diagram, ______ are added to the schematic diagram.

numbers

The contact symbols in the diagram indicates _____________.

off-delay normally open and normally closed timer contacts.

When a component is used to perform the function of start it is generally normally _____.

open

When a component is used to perform the function of start it is generally connected in _______ with the existing START button.

parallel

Solder melting type overloads are often called solder ______ overloads.

pot

______ diagrams show electrical components in their electrical sequence without regard for physical location.

schematic

____ push buttons combine the operation of a selector switch and push button in the same unit.

selector

_____ control is characterized by the use of push buttons, limit switches, pressure switches, and other sensing devices to control the operation of a magnetic contractor or starter.

semiautomatic

When a component is used to perform the function of stop in a control circuit, it will generally be connected in ______ with the motor starter coil.

series

All solenoids that operate on alternating current must have a(n) ____ coil.

shading

Relays and contactors operate on the ____ principle.

solenoid

Magnetic reversing starters generally change T leads ________ and ________ to reverse the motor.

1, 3

What is the voltage on which most magnetic control systems operate?

120V

There is a turns ratio of ____ between each primary winding and the secondary winding.

2.1

Line voltage devices may have contacts rated for 15 to ____ amperes.

20

The conductor size, fuse or circuit breaker size, and overload size are generally determined using the ____ Code and/or local codes.

National Electric

The contact symbols in the diagram indicates _____________.

On-delay normally open and normally closed timer contacts.

____ show components in their electrical sequence without regard for physical location.

Schematic