Deck 8: Basic Motor Controls

Question 1

Bimetal strip-type overload relays generally permit the trip current to be adjusted to between 85% and ____% of the heater rating.

A) 95
B) 105
C) 115
D) 125

Answer 1

C

Question 2

The ____ control circuit is often referred to as the basic circuit.

A) three-wire
B) forward-reverse
C) start-stop push-button
D) air-conditioning

Answer 2

C

Question 3

Describe the schematic symbols for push buttons.

Answer 3

A very common schematic symbol is the push button. Normally open push buttons are shown with the movable contact above and not touching the two stationary contacts. The symbol indicates that when finger pressure is applied to the movable contact, it travels downward and bridges the gap between the two stationary contacts. Normally closed push button symbols are drawn with the movable contact below and touching the stationary contacts. When pressure is applied to the movable contact it travels downward and breaks the connection between the two stationary contacts. Another very common push button symbol is the double acting push button. Double acting push buttons contain both normally open and normally closed contacts with one movable contact.

Question 4

____ switches are indicated by drawing a wedge shape below the movable contact of a switch symbol.

A) Axial
B) Stationary
C) Normally open
D) Limit

Question 5

A magnetic contactor or relay is basically an electrical ____ that closes a set of contacts when the coil is energized.

A) bar magnet
B) pole
C) dipole magnet
D) solenoid

Question 6

In a basic air-conditioning circuit there are two ____ switches in order to protect the compressor from extremes.

A) pressure
B) temperature
C) flow
D) float

Question 7

Motor control circuits can be divided into two major categories, one of which is ____.

A) three-wire
B) limit switching
C) float switching
D) deceleration

Question 8

What are the differences between the two types of thermal overload relays?

Question 9

What is the difference between overload protection and fuse or circuit protection?

Question 10

____ are intended to open the circuit when the current exceeds the full-load current rating of the motor by 115 percent to 125 percent.

A) Fuses
B) Overloads
C) Circuit breakers
D) Trip wires

Question 11

What are the major rules that should be followed when reading a schematic diagram?

Question 12

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

A) Wiring
B) Schematic
C) Control
D) Contact

Question 13

What are relays and contactors?

Question 14

A pressure switch is drawn by connecting a ____ to a line.

A) rectangle
B) square
C) semicircle
D) triangle

Question 15

If a contact is to be drawn ____ it is drawn so that the movable contact is above and touching the stationary contact.

A) normally closed
B) normally open
C) normally open held closed
D) normally closed held open

Question 16

There are two types of thermal overload relays, the ____ type and the bimetal strip type.

A) transistor
B) solder pot
C) rheostat
D) serrated wheel

Question 17

What does the abbreviation NO stand for with reference to switch contacts?

A) normally obverse
B) natural ordering
C) normally open
D) never open

Question 18

The current-sensing section of the overload relay can be ____, electronic, or thermal.

A) pressure-based
B) integrated
C) solar
D) magnetic

Question 19

All overload relays contain two separate sections, the ____ section and the control contact section.

A) voltage-sensing
B) voltage-modulating
C) current-sensing
D) resistance-modulating

Question 20

If the symbol shows the movable contact touching but below the stationary contact, this indicates that the switch is ____.

A) normally open held closed
B) normally closed held open
C) normally closed
D) normally open