Motors Part II Flashcards
An ohmmeter reveals one group of three and three groups of two. What kind of motor is this?
Wye
What is step one in lead ID for a delta motor?
Find three groups of Three
IEC Leads
A =
B =
C =
U
V
W
Second step in Delta ID?
Find centre points (resistances)
How many leads are on a six lead motor (lol)
six
There is only three leads in a JB. How many leads are in this motor and why is there only three?
There is six leads but only three are brought out to the JB. The other three are connected for us by the manufacturer
In a Wye-Delta starter, where are the overloads located?
In the phases
What does a wye-delta motor require?
Mechanical interlock, three contactors and three overloads (one set)
What kind of motor goes with a wye delta started?
delta
What are the labels on a wye delta motor starter?
1,4
2,5
3,6
What do we look for in a wye/delta started
Three groups of two leads
1,4
2,5
3,6
Name a few examples of applications for part winding motors
fans, pumps, refrigerant compressors, machine tools
What does a part winding motor require?
two contactors, two sets of overloads, no mechanical interlocks
What are the applications of an across the line started?
almost any except for fragile things that will get broken by a large bump from starting torque
Why would we use a part winding starter?
When we don’t need high starting torque
What transition type is in a part winding motor?
closed
What is the current reduction for a part winding motor starter?
60-65%
What is the torque reduction for a part winding motor started
60-65% squared
How many conductors go from the part winding starter to the motor?
six
Do all conductors in a part winding starter carry full current?
no
How many leads are in a part winding motor starter?
six
What are the labels in a part winding motor?
T1, T2, T3, T7, T8, T9
How many groups of three are there in a part winding motor starter?
two groups of three
What is the most common winding method in a part winding motor?
Wye
What are the two types of motor starters?
across-the-line, reduced voltage
What is the typical inrush current when using an across the line starter?
500-600%
What is the typical starting torque when using an across the line starter?
150%
Where are the motor leads connected in an across the line starter?
directly to the source
A motor capable of a part winding start has ___
two or more sets of three phase windings
In a part winding motor only ___ is energized at start
one coil
What is the percentage of inrush current in a part winding start in comparison to an across the line start?
60 - 65%
Why would we use a reduced voltage starter?
when the high inrush current could cause excessive volt drop
What does a reduced voltage starter do?
reduces the inrush current
Besides current, what do reduced voltage starters also do?
reduce starting torque
Why may we want to reduce starting torque?
Some loads, such as fragile ones may be damaged by the bump from the starting torque
What is the main timer in motor starters?
Time delay on energization
What are the terminals we will see on a TDOE?
TO (Timed open) and TC (Timed closed)
In an autotransformer RV start, starting current to the motor is proportionate to ____
starting voltage
What is the transition type of a wye delta motor?
open but can also be closed
What is the reduction in current at start of a wye delta motor?
1/3 of FVS
What is the voltage reduction at start in a wye delta motor starter?
Root 3 of FVS
What is the formula to size the overload of an autotransformer starter?
FLA x Service factor multiplier
What are the main types of motor starters that we will need to know?
Across the line/full voltage, wye delta, part winding, autotransformer
What is the motor current reduction in an autotransformer starter motor?
I motor = %tap x I FVS
What is the line current reduction in an autotransformer starter?
I FVS x %Tap^2
What is the only motor starter where the line current reduction will be different from the motor current reduction?
autotransformer
What is a closed transition?
When there is always a path for current from start to finish
What is the torque reduction in an autotransformer starter?
Torque FVS x % Tap^2
In a closed transition, is there always a path for current to flow from start to run process?
yes
What is an open transition?
When there is a break in the path for current to flow from start to run even if it is for a moment
All autotransformers are ___ transition
closed
In a wye delta starter, where are the overloads located?
in the phase
