Motor Starters Flashcards
Motor starters can be of two main types what are they
Across the line {FVS}
Reduced voltage starters
(Reduces V at start, full V for run)
What is the most common starting method?
Full voltage/ across the line start
What are the terminal marking for a part winding starter
T1-T3 and T7-T9
List the terminal marking on a wye-delta starter.
T1-T6
What is the purpose of a reduced voltage starter
To reduce the inrush current at start
List two starting modes that are common on electric soft starters
Ramp start
And current limiting start
True or false
the load to a rotary converter must not be connected until the converter reaches its rated speed and is supplying 3 phase power
True
True or false
Static phase converter can supply more than one load
False
Can only supply one load at a time
True or false
A rotary phase converter can supply more than one load
True
Can a static phase converter supply power to a single three phase motor?
Yes it can
True or false
Static phase converts are more balanced than Rotary phase converters
False
Rotary phase converters are the balanced of the two types
True or false
Single phase motors are available above 15 hp are often found above 5hp
False
Not available above 15 hp and rarely found above 5hp
By how much does a wye/delta starter reduce the starting line current, compared to a full voltage start?
Starting line current would 1/3 smaller
True or false
Starting torque is reduced by 1/3 of what it would be if the motor was started at full voltage.
True
The overloads of a wye delta starter are based on the line current.
True or false?
False they are based on the phase current (57.7% of the line current)
A continuity test on a dual voltage delta motor would show how many groups of leads?
3 groups of 3 leads
True or false
Dual voltage motors reduce stocking costs for manufacturers and wholesalers
True
True or false
A continuity test on a dual voltage wye motor would reveal 1 group of three leads and 3 groups of two leads.
True
A single voltage wye start delta run motor is required for wye/delta starting
True or false
True
A continuity test on a single voltage six lead motor would reveal what?
3 groups of two leads
What are the three basic functions of a vfd?
Rectifier
Filter
Inverter
What does the rectifier do?
Turns ac supply into dc and supplies the dc voltage to the dc link
What does the filter do?
Provides a clean and smooth DC source for the inverter
What does an inverter do?
Converts the DC to an AC voltage which is voltage a frequency controlled
True or false
Changing the timing of pulse cycles will change the output frequency when using pulse width modulation.
True
Will changing the width of the pulses in PWM change the output voltage?
Yes
What is the Igbt?
It’s is a high current fast switching voltage controlled device. In charge of the on/off switching of the pulse.
True or false
I order to not exceed the fla rating of the motor, the motor voltage (E) must be lowered as frequency is lowered
True
V/Hz ratio
What must a nameplate state to indicate a motor is compatible with a vfd
Inverter duty
What is open loop feedback
It means the vfd runs according to preset values set within the programming
Describe closed loop feedback
On top of running a t preset values. The vfd relies on feedback and responds to sensing devices accordingly
What are the four main pieces of info needed from motor in order to pick a starter
Hp rating
Voltage
FLA
Service Factor
What is a linear load and name an example
Impedance stays the same when voltage and current vary
A résister is linear
What is a non linear load and name an example
When the Z changes as V changes
Examples are motors, VFD’S, electronic ballasts, cpu power supplies
Name 3 problems that occur from harmonic currents
Excessive neutral current
Additional hysteresis losses
Harm to the motor connected to vfd
How are harmonics reduced?
Line reactors installed on the line side of the vfd
Harmonic filters
Harmonic réduction built in to vfd
What do vfd cables require to prevent RFI (radio frequency interference)
Shielding or continuous metal armour
How far should vfd cables be from control and signal cables? And if they cross paths, at what angle must they do so
300 mm
90 degrees
What does the carries frequency of a vfd do
Determine the actual number of pulsée the drive produces
A vfd changes the speed of a motor by changing what two parameters
Voltage and frequency
What does the V/hz ratio help determine
The motor current
What is torque boost
V/hz is programmed to provide higher voltage which produces higher current and torque at lower frequency operation
What are the two types of full voltage starters?
Magnetic and manual
Which starter is also a disconnect means
Manual starter
Name the terminals of a part winding motor
T1 - T3
T7 - T9
Describe briefly how a part winding starter works
Full voltage is applied to the first group of windings
After a preset time, for voltage is applied to the second group of windings so that both groups are energized
A time delay on energization is also known as
On delay
A time delay on D energize Asian is also known as
Off delay
What does it mean when contacts are labeled TO or TC
Timed to open
Timed to close
What is the most common starting method
Across the line
Full voltage start
The overload setting of a wye delta start are based on what percentage of fla
57.7%
What is an Electronic soft starter
Reduces starter currents with electronics
Describe ramp starting
Starting current is increased at a constant rate
Describe current limit starting
Restricts starting current to a maximum
Describe kickstarting
Initial current surge for hard to start loads
Which load is harder to start, variable torque or constant torque
Constant torque
What are the two types of phase converters
Rotary and static
What does a basic phase converter do
Convert single phase power to three phase power
Name a few places where you could find phase converters
Farms, small industrial plants, woodworking shops, metal fabrication shops
What are the advantages of fractional horsepower single phase motors
They are cheaper and more common than three phase
What are the advantages of three phase motors
More efficient, smaller, quieter, simpler
Larger horsepower are cheaper and more common
Briefly describe how a rotary phase converter works
Induction motor generator and capacitors help create a third phase. This third phase along with the original two are put together to create three phase power roughly 120° apart
True or false a rotary phase converter can supply only a single motor
False a rotary phase converter can supply several motors
What are the two horse power ratings for a rotary phase converter
Maximum starting horse power equals largest motor
Maximum running horse power equals all motors added together
True or false. A static phase converter can supply several motors
False. A static phase converter can supply only a single motor
Which phase converter has a more balanced out put
Rotary phase converter’s are more balanced
True or false. Static phase converter’s are cheaper than Rotary phase converters
True. Static phase converters don’t include an induction motor generator
What are the groupings of leads of a nine lead Delta motor
Three groups of three leads
What are the groupings of leads of a nine lead wye motor
One group of three leads And three groups of two leads
Which motor has a group of three leads that has eight ohms between them
A dual voltage nine Lead wye motor
