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ABE 2 First Exam > Module 3: Electric Motors > Flashcards

Module 3: Electric Motors Flashcards

1
Q

device used to convert electrical energy into mechanical energy

A

electric motor

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2
Q

considered to be a more efficient means of converting energy into mechanical energy compared to gasoline and diesel engines

A

electric motor

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3
Q

energy conversion efficiency of electric motor is 50 to 99%

true or false

A

true

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4
Q

energy conversion efficiency of a diesel engine is ___-36%

A

30

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5
Q

energy conversion efficiency of a gasoline engine is 50-99%

true or false

A

false; 25 to 30 %

50-99% is for electric motor

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6
Q

main application of electric motor

A

used as prime movers for stationary and indoor equipment such as those for processing of farm products and by-products

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7
Q

advantages and key features of electric motors

A
  • low initial cost
  • compact
  • long life
  • simple to operate
  • quiet operation
  • no exhaust fumes
  • potential for automatic control

+++
- available in different hp sizes
- relatively inexpensive to operate

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8
Q

different hp sizes of electric motors

A

fractional hp sizes
- 1/4
- 1/2
- 3/4

integral hp sizes
- 1
- 1 1/2
and so forth…

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9
Q

common hp sizes of electric motors used

A

fractional hp sizes
- 1/4, 1/2, 3/4 hp sizes

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10
Q

costs of operating electric motor, diesel and gasoline engines

A

elec motor - Php 8.75/kW-hr
diesel engine - Php 9.17/kW-hr
gasoline engine - Php 23.85/kW-hr

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11
Q

disadvantages of using electric motor

A
  • not adapted to mobile applications unlike engines
  • used only in farms with elec lines
  • affected by power outtages
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12
Q

classification of electric motor based on elec service

A
  1. single-phase alternating current (<5 hp)
  2. three-phase alternating current (>5 hp)
  3. direct current (use of storage battery)

most common ay #1

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13
Q

basic electrical principles

A
  1. electromagnets
  2. electromagnetic induction
  3. alternating current
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14
Q

2 major parts of an electric motor

A
  1. stator - stationary part
  2. rotor - rotating part
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15
Q

select a motor whose torque output is equal to the torque required by the load

true or false

A

false; torque output should always be greater than the requirement

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16
Q

determines the size and capacities of the electrical installations needed to operate the motor (transformer capacity, wire size, breaker capacity, switch, etc.)

A

starting current requirement

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17
Q

this is determined by the kVa rating of the motor indicated by a motor code letter

A

starting current requirement

18
Q

the temperature rise shall not exceed the limit for the insulation class when the motor is loaded to its rating or its service factor load

true or false

A

true

19
Q

motors are built with how many insulation classes that can withstand only certain levels of operating temperature

A

four insulation classes

20
Q

refers to how frequently the motor is started and how long it will run each time it is started

A

duty rating

21
Q

2 types of duty rating

A
  1. continuous duty rating
  2. intermittent duty rating
22
Q

duty rating

motor is operated for more than an hour without rest

A

continuous duty rating

23
Q

duty rating

operated for only few minutes at a time with rest between operations

A

intermittent duty rating

24
Q

case or housing which prevents the operator from accidental contact with energized parts and protect the motor from physical damage

A

enclosure

25
Q

2 types of enclosure

A
  1. open type
  2. totally-enclosed
26
Q

enclosure

allows easy movement of air through the inside of the motor by providing slots or holes in the end shields or frame where the air can pass through

A

open type enclosure

27
Q

enclosure

does not allow entry entry of air inside the motor

fan blows air on the outside surface of the frame to dissipate heat

A

totally-enclosed enclosure

28
Q

fins are constructed on a motor’s enclosure to??

A

increase the surface are for heat dissipation

29
Q

indicates the maximum load that can be successfully carried by the motor if it is to operate continuously and remain within a safe temperature range

A

service factor

30
Q

the service factor is multiplied by the horsepower rating to give the _________ ______ the motor can sustain

A

maximum load

31
Q

carries a good deal of essential information about the motor and should be referred to when specifying, buying, installing, replacing, operating and repairing motors

A

motor nameplate

32
Q

for most residential and agri structures, this type of motor is widely used

A

alternating current motor

33
Q

this is produced from winding insulated wire around a soft iron core

A

electromagnet

34
Q

as the current passes through the coil, what is produced?

A

magnetic field (that has 2 diff poles: north and south which is based on the direction of current flow)

35
Q

when a conductor passes through a magnetic field, what is induced?

A

a current (electromagnetic induction)

36
Q

in electromagnetic induction, the induced voltage is controlled by different factors which are?

A
  • strength of the magnetic field
  • the rate at which the conductor is cutting the flux lines of the magnetic field
  • number of conductors in which it changes its direction in an interval
37
Q

a current in which it changes its direction in an interval

A

alternating current

38
Q

main part of the motor that is made of paired slotted cores of soft iron sections

A

stator

39
Q

main part of motor that is referred to as the armature of the motor

A

rotor

40
Q

in a motor, the cores are wind with insulated copper that forms different pairs of magnetic poles

then the stator windings are connected to an ___ sources to form ________

A

AC source; electromagnets

41
Q

normal ambient temp for motor operating is ______

A

40 ‘C

42
Q

formula for computing starting current requirement (amp)

A

A = output power x motor horsepower / voltage rating

ABE 2 First Exam (11 decks)

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