L1 - Motor - Review Quiz

Question 1

What is the difference between a schematic diagram and a wiring diagram?

Answer 1

Schematic:
- uses symbols to identify components.
- interconnecting lines to show electrical continuity

Wiring:
- shows the relative layout and how the component are wired

Question 2

What is low voltage release? (LVR)

Answer 2

• 2 wires
• When after a power failure: the machinery restarts on its own

Question 3

On a magnetic starter (combination style) what is horsepower rated?

Answer 3

• The contact (power)
• The disconnect switch
• The magnetic contactor

Question 4

What is another name for a zero speed switch?

Answer 4

Plugging switch

* Zero-speed switches are used in circuits to provide either plugging action (momentarily reversing a motor to stop it) or anti-plugging action (preventing the reversal of a motor until it has come to a rest).*

Question 5

How does a latching relay work? What is the purpose of the unlatching relay?

Answer 5

Latching relay is energized after de-energization is mechanically held in place to release energize unlatching coil.

*** A latching relay is an electromechanical switch commonly selected when the operator must control (either switch off or amplify) a large amount of current flow. It will remain in the last position it was when last powered, whereas a non-latching relay will return to its typical position.’

Question 6

What is the purpose of a limit switch?

Answer 6

To prevent over-travel

* A limit switch is an electromechanical device operated by a physical force applied to it by an object. Limit switches are used to detect the presence or absence of an object. These switches were originally used to define the limit of travel of an object, and as a result, they were named Limit Switch.*

Question 7

What is the dotted line between the forward coil and the reverse coil on a schematic drawing?

Answer 7

Mechanical interlock

* Represented on schematic diagrams as a dotted line between the two coils, a mechanical interlock is a physical barrier that is pushed into the path of one coil’s armature by the movement of the adjacent coil. This means that even if both coils are energized, only one armature will be able to pull in fully.*

Question 8

Name three pressure switch types

Answer 8

1- Bourdon tube: when the pressure inside the tube increases the closed end of the C opens out, thus the displacement of the closed end becomes a measure of the pressure. A C-shaped Bourdon tube can be used to rotate, via gearing, a shaft and cause a pointer to move across a scale.

2- Bellows: When pressure is applied to the closed-end, such as in the animation below, the bellows will be compressed. The closed-end will move upwards and the link, which is the rod in between the closed-end of the bellows and the transmission mechanism, will go up and rotate the pointer.

3 - Diagram: A diaphragm is nothing more than a thin disk of material which bows outward under the influence of a fluid pressure.

* Each of these devices converts a fluid pressure into a force. If unrestrained, the natural elastic properties of the element will produce a motion proportional to the applied pressure.*

Question 9

Name 2 type of timers

Answer 9

• On-delay (electronic)
• Off-delay (pneumatic)

Question 10

What is the purpose of a control relay?

Answer 10

To offert more contacts and a diverse control cct.

Question 11

What type of oil is used in a dashpot timer?

Answer 11

Silicon

Dashpot timer: The dashpot timer is a fluid time-on-timer that can be used in definite time motor acceleration starters and controllers. A dashpot timer is a container, a piston, and a shaft. The dashpot timer functions when a magnetic field forces a piston to move within a cylinder when the coil is energized.

Question 12

On/off delay timers can be changed by rotating the timer face of X degrees

Answer 12

180

Question 13

Name 2 type of contactors

Answer 13

1- Plunger: Vertical lift
2- Clapper: front closing

Question 14

What is the difference between a magnetic starter and a contactor?

Answer 14

• Magnetic starter has O/L protection

-Magnetic coil is a part of the starter

Question 15

What is the main purpose of all motor starter?

Answer 15

To start, stop and offer O/L protection

Question 16

What is the main purpose of for overload protection in motor starter?

Answer 16

To protect the motor from excessive O/L current.

Question 17

What does the term ‘maintained stop’ mean?

Answer 17

When pushed stays in the open/close state. Must be pulled back to original position.

Question 18

What type of switch does not have to be horsepower rated?

Answer 18

Isolating switch. Doesn’t have to interrupt locked rotor current

Question 19

What is the difference between a timed contact and an auxiliary contact on a on delay timer?

Answer 19

On a timer:

• Auxiliary contact closes the ?
• instant the coil is energized
• timed contact - times open or closed

Question 20

What does DPDT mean?

Answer 20

Double-pole Double-throw

Question 21

How do we wire stop buttons in a circuit? Start buttons?

Answer 21

• Stops in series
• starts in parallel

Question 22

Do we ever have an opportunity to wire a coil in series?

Answer 22

No!

In parallel only.

Question 23

What is the difference between low voltage protection (LVP) and low voltage release (LVR)

Answer 23

LVP: 3 Watts. Won’t restart during to seal-in contact.

LVR: X Watt

Question 24

How many wires go to a simple stop start station?

Answer 24

3wires

Question 25

What is meant by mushroom head?

Answer 25

Head of button similar to mushroom. Easy to strike.

Question 26

Draw the overload symbols for the power cct. For the control cct

Question 27

How many wires go to a stop/start/reverse station?

Answer 27

4 wires

Question 28

Describe how anti-plugging works in a circuit.

Answer 28

• Switch opens until motor comes to complete stop.

A forward/reverse circuit can use two off-delay timers to provide anti-plugging action in an anti-plugging circuit. This circuit utilizes two off-delay coils to prevent the forward and reverse coils from being energized until ten seconds after the stop button has been pressed.

Question 29

Name 2 types of armature s (mechanism used to close the contacts on a magnetic)

Answer 29

• Clapper:
• Vertical lift:

* The armature is an integral part of the motor (or generator), as this is the component that carries the alternating current (AC) in an electric machine. The armature conducts AC, even on Direct Current (DC) machines using the commutator (which reverses current direction every so often) or due to electronic commutation.*

Question 30

What is a solder pot? Name another type of heating element.

Answer 30

• O/L device that uses silver solder as a melting agent
• bimetallic element

Question 31

What is another name for jogging?

Answer 31

Inching

* Jogging refers to repeated starting and stopping of a motor in short bursts to perform a particular movement such as moving a crane to a particular location. Jogging should not be done more than 5 times in a minute. This is because jogging can cause the motor to overheat.*

Question 32

How do we change direction on a simple 3ø AC induction motor?

Answer 32

Interchange any ‘z’? T leads

Question 33

How does a off delay timer work?

Answer 33

• Energize coil - timed contacts close/open
• De-energized coil - times open/or close

Question 34

How does an on delay timer work?

Answer 34

Energize coil - time opens or closed

De-energized coil - instantly opens or closes

With ON-delay operation, the Timer receives an input and then an output signal is output by switching the Timer contacts after a set time delay. This name is used because there is a delay between when the input signal is received (i.e., turns ON) and when the output signal is output.