Electrical Motor Controlllll

meow

Which of these is a component in a typical three-phase squirrel-cage motor?

-Copper bars

-End rings

-Iron core

-All of the above

All of the above

What are the 3 voltages of a Wye system?

208 VAC

480 VAC

600 VAC

If the service factor for a motor is NOT GIVEN on the nameplate, WHAT SHOULD YOU ASSUME the service factor to be?

1

Three-phase power is transmitted in phases that are how many degrees apart?

120 degrees

What is the accepted standard in the United States for safely installing and maintaining electrical systems and equipment called?

NEC

A ground fault occurs when:

One of the phases becomes grounded

Can a grounded neutral wire be used as an equipment ground?

NO!!! Neutral does NOT equal ground

In a 480VAC 3-phase wye system with a neutral, what are the PHASE TO PHASE and PHASE TO NEUTRAL voltages? 

PTP 480VAC

and

PTN 277VAC

A fuse is chosen based on what rating found on the motor nameplate?

Full load current

What on a motor’s nameplate is used to determine how much output power a motor can safely produce above its rated output power?

Service factor

In an electrical system, what part of the system is normally connected to an equipment ground bus?

-Metal Conduit

-Metal Enclosures

-Transformer Cases

-All of the above

All of the above

Which conductor provides a common return path to source for the conductors that carry current in a system?

Neutral

If a motor is able to be configured for both high and low voltage, and is running wired for high voltage, is the current draw INCREASED, DECREASED, or does it STAY THE SAME?

Decreased

Which of the following is a basic requirement for a typical motor installation?

-Controller

-Short Circuit Protection

-Disconnect

-All of the above

All of the above

When do overloads open?

When the motor draws excessive current over time

What kind of protection on a manual starter will PREVENT THE AUTOMATIC RESTART of a motor when recovering from a power loss?

Undervoltage protection

What opens and closes power wires to start and stop a motor?

Motor controller

What is a motor controller that also includes overload protection called?

Motor starter

Does a time-delay fuse only have 1 element?

NO!!! They usually have 2

Will the contacts of a manual starter remain in the actuated position when power is lost?

Yes

What is TRUE about low voltage protection?

-When power is lost, requires the operator to turn the loads back on

-Uses circuit interruption devices

-Protects against sudden activation of a machine

-All of the above

All of the above

If a an overload that uses a coil to sense the level of motor current has tripped, what RESISTANCE reading will you see ACROSS that coil if there is an OPEN? 

OL (out of limits)

What are the 2 basic TYPES of manual motor starters?

Fractional horsepower

and

Integral horsepower

The relationship between the input voltage and output voltage of a transformer is based on the: 

Turns ratio

What is the turns ratio of the diagram?

2:1

What is the secondary voltage of the diagram?

60 VAC

What is the turns ratio of the diagram?

1:3

What is the secondary voltage of the diagram?

360 VAC

What is this symbol called?

Transformer (with ferromagnetic core)

Why are control transformers called isolation transformers?

-Problems in power less likely to damage control

-Problems in control less likely to damage power

-Ferromagnetic core isolates primary from secondary

-All of the above

All of the above (since the core isolates primary from secondary, problems from either side are less likely to affect each other)

What is the most important guideline when sizing a transformer?

Pick one that can safely provide max current

How would you test the transformer below for a short between the primary and secondary? 

One lead on H1, other lead on X2

(H2 to X1 also works)

A reading of what tells you there is NOT a short between the primary and secondary coil.

-more than 0 ohms

OR

-OL

OL

If you were checking the secondary coil for an open, the meter would read what if the coil is open?

-more than 0 ohms

OR

-OL

OL

Why are there usually two coils on the primary of a control transformer, while only one on the secondary?

Plant supply may be different voltages

What connections would you make on the primary winding if your facility used 208vac but you needed 120vac for your control circuit?

L1-H2, L2-H1

What is the turns ratio if the primary has 400 turns and the secondary has 100 turns?

4:1

What are the three classifications of electrical control systems?

Manual, semiautomatic, automatic

When does the green light illuminate in the circuit?

Power is on and PB1 is not pressed

How many pushbuttons are in this circuit?

1

How many SETS of contacts are in this circuit?

2

What do you call the small numbers that show the contacts ASSOCIATED with an output?

Cross reference number

What type of logic element does this circuit use?

NOT

What type of logic element does this circuit use?

NOR

What is this symbol called?

Thermal breaker

A series of moves a machine makes to perform a task is called a:

Sequence of operation

During sequence control process three steps take place, what are those steps?

Look out inputs, perform logic, update outputs

What input conditions must exist in the circuit below for the green light to illuminate?

PB3 stays closed (unpressed)

SS to the right

PB2 is closed (pressed)

There are six rules to ladder diagrams:

1. All Components must be labeled

2. All Conductors must be Numbered

3. All Lines Must Be Numbered

What are the remaining 3 rules to ladder diagrams? 

ONLY show CONTROL devices

ONE LOAD per line

OUTPUTS on the RIGHT

What is a method of representing one component with several symbols in various locations on a ladder diagram?

Detached symbology

When a relay is connected so that it continues to energize itself after a momentary input is removed, the circuit is called what?

Seal in circuit

To test a relay coil OUT-OF-CIRCUIT, you would measure:

Resistance (it is the only thing that you can actually measure when OUT of the circuit)

Which of the following is not a typical input device used for two-wire control circuits?

-Pressure Switch

-Float Switch

-Pushbutton Switch

-Proximity Switch

Pushbutton switch

Name the two types of Control Relays:

General purpose, Machine control

This circuit is an example of:

-Control Circuit

-Three Wire Control

-Memory Logic

-All of the above

All of the above

Which of the following electrical control types would most commonly be used on a sump pump application?

-Three wire control

-Two wire control

-Always energized control

-Four wire control

Two wire control

What are the initial states of the indicator lamps?

Red is off, green is on

In order to turn the green light off, what must be true?

-Control relay CR1 must be deenergized

-Control relay CR2 must be deenergized

-PB1 should be pressed

-Control relay CR1 must be energized

Control relay CR1 must be energized

If the normally open contacts of CR1 became shorted, what would happen to the lamps?

Red is on, green is off

The contacts of a control relay are used as an input, output, or both?

Input (the COIL would be an output)

If the switch is closed in this circuit, what will happen?

The fuse will blow because a ground fault WILL occur

How do you reverse the rotation of any three-phase motor?

-Connecting L3 to T1 and L1 to T3

-Interchange T1 and T3

-Interchange any 2 of the 3 power supply lines

-All of the above

All of the above (even though T1 and T3 is the standard, ANY of the wires being switched could work)

Fuses are rated for what two main characteristics?

Current and voltage

If the holding contacts on a seal-in relay circuit are failed in the open condition, you should observe that:

-The output turns off after releasing the start button

-The output turns on as soon as power is applied

-The output will never energize

-The fuse will immediately blow

The output turns off after releasing the start button

When reversing the direction of a three-phase motor, NEMA and IEC recommend reversing WHICH motor connections?

T1 and T3 (you can technically switch any motor connection, but NEMA specifically wants T1 and T3 switched)

Which of the following is a component of a reversing magnetic motor starter?

-Forward contactor

-Reverse contactor

-Overload protection

-All of the above

All of the above

Based on the wiring diagram shown, how should the L and T connections be wired if the drum switch is placed a reverse position?

L1 to T2, L2 to T1, L3 to T3

What provides a magnetic method of changing the direction of rotation for a motor?

Reversing magnetic motor starter

What function does a normally open auxiliary contact of a magnetic motor starter serve?

-Power the motor

-Seal in the circuit

-Interlocks forward and reverse coils

-Overload protection

Seal in the circuit

Which interlocking method is shown in the reversing motor control diagram?

Pushbutton interlocking

Possible causes for an overload to trip constantly is:

-The trip setting is incorrect (IEC)

-The incorrect heater size is being used (NEMA)

-Both of these

Both

To determine if an indicator lamp has failed, measure the lamp's…

Resistance

Which of the following is NOT a possible cause when none of the contacts on a motor contactor change status when the coil is energized?

-Mechanical problem with contactor

-Partial short in coil

-Coil is open

Partial short in coil

Should resistance readings across the windings of a motor be HIGH or LOW?

Low

Which of the following is a method of testing a component?

-Out of circuit test

-Mechanical test

-In circuit test

-All of the above

All of the above

If none of the contacts of a MANUAL switch change status when the operator is activated, what is the most probable cause?

-Mechanical problem with operator

-Contacts are shorted

-Contacts are open

Mechanical problem with operator

To test a relay coil out-of-circuit, you would measure…

Resistance

Is the process of finding the cause of a machine malfunction called fault hunting? T/F

No lol wtf is that, false (it is actually called troubleshooting)

The first step in the system troubleshooting process is to:

Identify the problem

What is a device that can be used to measure several different electrical characteristics?

DMM

Does a circuit need to be disconnected to use a clamp on ammeter to measure current?

No, it needs to be CONNECTED to even have current

Do you need to change the voltage range on a wiggy (voltage tester)?

No

What is the first step when using a DMM to measure continuity?

Set the switch to the continuity function

The IEC developed a standard to rate DMMs based on the what?

Max voltage spike meter can handle

What method assumes that measurements BEFORE the cause of the problem will be normal and measurements AFTER the cause will not be normal?

Half split method

With the test probes placed in the circuit as shown in the figure, what should the voltage reading be if the start pushbutton is pressed, assuming the circuit is operating properly?

Full control voltage

In a ladder logic control circuit, the signal measured is usually what?

Voltage

Limit switches are often used as safety _____

Interlocks

Limit switch symbols are sometimes drawn in the actuated or _______ position.

Held

Which limit switch ladder diagram symbol represents a N.C.H.O condition?

Limit switch D

Which limit switch represents a N.O.H.C condition?

Limit switch B

What component is normally used in an air compressor to change states when the pump has compressed air to a certain setpoint?

Pressure Switch

A pressure switch is known as a ________-__________ type, which means that it will suddenly change states when actuated.

Snap-acting

The actuator in a pressure switch is a plunger which is attached to a __________.

Diaphragm

The difference between the set-point pressure and the reset pressure is called the deadband or ____________.

Differential

What device is being used to control the on/off status of M2?

Pressure Switch

What sequence of operation needs to happen to turn on the Main Motor? (just say what needs to be activated)

Start PB pressed, PS-1 closed

What happens in the circuit if the Selector switch is placed in the right position?

System will run in auto

What 3 basic components do timer relays consist of?

Coil, contacts, timing mechanism

What are the 2 basic types of time delay relays?

Off delay, on delay