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Electrician 3rd Year > Motors Part II > Flashcards

Motors Part II Flashcards

1
Q

An ohmmeter reveals one group of three and three groups of two. What kind of motor is this?

A

Wye

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2
Q

What is step one in lead ID for a delta motor?

A

Find three groups of Three

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3
Q

IEC Leads
A =
B =
C =

A

U
V
W

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4
Q

Second step in Delta ID?

A

Find centre points (resistances)

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5
Q

How many leads are on a six lead motor (lol)

A

six

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6
Q

There is only three leads in a JB. How many leads are in this motor and why is there only three?

A

There is six leads but only three are brought out to the JB. The other three are connected for us by the manufacturer

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7
Q

In a Wye-Delta starter, where are the overloads located?

A

In the phases

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8
Q

What does a wye-delta motor require?

A

Mechanical interlock, three contactors and three overloads (one set)

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9
Q

What kind of motor goes with a wye delta started?

A

delta

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10
Q

What are the labels on a wye delta motor starter?

A

1,4
2,5
3,6

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11
Q

What do we look for in a wye/delta started

A

Three groups of two leads
1,4
2,5
3,6

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12
Q

Name a few examples of applications for part winding motors

A

fans, pumps, refrigerant compressors, machine tools

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13
Q

What does a part winding motor require?

A

two contactors, two sets of overloads, no mechanical interlocks

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14
Q

What are the applications of an across the line started?

A

almost any except for fragile things that will get broken by a large bump from starting torque

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15
Q

Why would we use a part winding starter?

A

When we don’t need high starting torque

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16
Q

What transition type is in a part winding motor?

A

closed

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17
Q

What is the current reduction for a part winding motor starter?

A

60-65%

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18
Q

What is the torque reduction for a part winding motor started

A

60-65% squared

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19
Q

How many conductors go from the part winding starter to the motor?

A

six

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20
Q

Do all conductors in a part winding starter carry full current?

A

no

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21
Q

How many leads are in a part winding motor starter?

A

six

22
Q

What are the labels in a part winding motor?

A

T1, T2, T3, T7, T8, T9

23
Q

How many groups of three are there in a part winding motor starter?

A

two groups of three

24
Q

What is the most common winding method in a part winding motor?

A

Wye

25
Q

What are the two types of motor starters?

A

across-the-line, reduced voltage

26
Q

What is the typical inrush current when using an across the line starter?

A

500-600%

27
Q

What is the typical starting torque when using an across the line starter?

A

150%

28
Q

Where are the motor leads connected in an across the line starter?

A

directly to the source

29
Q

A motor capable of a part winding start has ___

A

two or more sets of three phase windings

30
Q

In a part winding motor only ___ is energized at start

A

one coil

31
Q

What is the percentage of inrush current in a part winding start in comparison to an across the line start?

A

60 - 65%

32
Q

Why would we use a reduced voltage starter?

A

when the high inrush current could cause excessive volt drop

33
Q

What does a reduced voltage starter do?

A

reduces the inrush current

34
Q

Besides current, what do reduced voltage starters also do?

A

reduce starting torque

35
Q

Why may we want to reduce starting torque?

A

Some loads, such as fragile ones may be damaged by the bump from the starting torque

36
Q

What is the main timer in motor starters?

A

Time delay on energization

37
Q

What are the terminals we will see on a TDOE?

A

TO (Timed open) and TC (Timed closed)

38
Q

In an autotransformer RV start, starting current to the motor is proportionate to ____

A

starting voltage

39
Q

What is the transition type of a wye delta motor?

A

open but can also be closed

40
Q

What is the reduction in current at start of a wye delta motor?

A

1/3 of FVS

41
Q

What is the voltage reduction at start in a wye delta motor starter?

A

Root 3 of FVS

42
Q

What is the formula to size the overload of an autotransformer starter?

A

FLA x Service factor multiplier

43
Q

What are the main types of motor starters that we will need to know?

A

Across the line/full voltage, wye delta, part winding, autotransformer

44
Q

What is the motor current reduction in an autotransformer starter motor?

A

I motor = %tap x I FVS

45
Q

What is the line current reduction in an autotransformer starter?

A

I FVS x %Tap^2

46
Q

What is the only motor starter where the line current reduction will be different from the motor current reduction?

A

autotransformer

47
Q

What is a closed transition?

A

When there is always a path for current from start to finish

48
Q

What is the torque reduction in an autotransformer starter?

A

Torque FVS x % Tap^2

49
Q

In a closed transition, is there always a path for current to flow from start to run process?

A

yes

50
Q

What is an open transition?

A

When there is a break in the path for current to flow from start to run even if it is for a moment

51
Q

All autotransformers are ___ transition

A

closed

52
Q

In a wye delta starter, where are the overloads located?

A

in the phase

Electrician 3rd Year (6 decks)

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