Motor Starters Flashcards
What are the 2 parts of a magnetic motor started
Contactor and overload device
Do overload devices sense current or voltage
Current
What class of started come pre wired with the overload attached
NEMA
What starter has exposed live terminals and must be contained in an enclosure
NEMA
What are the 7 parts of a contactor
Stationary contact, moveable contact, pressure springs, operating coil, stationary electro magnet, magnetic shading coil, movinv armeture
What circuit are the power contacts in
Power cct
What cct are the holding contacts in
Control cct
What voltage must the operating coil be rated for
Control cct voltage
What is a control transformer used for in motor starters
To step down supply voltage to power a extra low voltage to supply proper voltage to the operating coil
What is the advantage to using an ELV coil in a starter
Less strict wiring restrictions
What rating must contacts in a motor starter match
FLC OFmotor
Do the holding contacts have to be fated as high as power contacts
No
Can auxillary contacts be used for motor starting and stopping
No
What do overload devices protect against
Overheating and damge to cct conductors and motor
What do O/L devices monitor
Current
What are the 2 ways an ac motor can be wired
2 wire single phase 3 wire 3 phase
If a nameplate has a voltage rating of 115 v what is the nominal or source voltage used
120v
Mechanical power output is the equivalent to what in a motor
Horsepower
1 horsepower is how many watts
746w
Motors draw more or less current at higher voltages
Less
If your operating coil is rated lower than supply voltage what must be done
A transformer needs to be used to step down the voltage
What 4 factors must be considered when selecting a nema starter
FLC of motor
Voltage fating of motor
HP rating of motor
Duty of motor (continuous or jogging)
What must be considered when selecting an o/l device
Full load current and service factor of motor
Can overload devices be adjusted
Sometimes
What are the 3 types of magnetic motor starters
Full voltage/across the line
Reduced voltage
Reversing motor starters
What type of starter gives full voltage right as the motor starts
Full voltage/ across the line
What starter type slowly ramps up voltage as the motor starts
Reduced voltage
What type of starter has 2 different contacts to swap the direction it runs
Reversing
What nema terminal feeds the control cct
1
Nema terminals 2&3 represent what
Holding contacts
Where does terminal 2&3 represent
Holding contact
What iec terminals do you attach auxilllary devices too like lights
A1, a2, or 13 , 14
What is ambient temp rating of a motor
Temp the medium used to cool the motor
What produces heat in a motor
Core losses, eddy currents, hysteresis, bearing friction, i2r losses
Do overload devices always open under short cct
Not always
What are the 2 sections if an overload relay
Current sensing section
Current responding section
What are the 2 main types of overload devices (principals they work in)
Thermal and magnetic
What 3 thing ls must you consider when sizing an o/c for a motor
FLC of motor, type of o/c device/ type of motor
What must motor o/l protection be based off
FLC of motor, service factor of motor
If a motors service factor is not listed what do we take it as
1
A motor has a service factor of 1.15 what do you multiply FLC by to size your O/L
1.25 or 125%
If motor service factor is below 1.15 what do you multiply FLC by
1.15 or 115%
If no horsepower is listed on motor what value must the fuse be able to interrupt
Locked rotor current
What are the 3 sections of motor control ccts
Stopping, holding, starting
If holding contacts are placed in the stop section of a cct what affect will it have on motor operation
Starting and running of the motor
If holding contacts are placed in the start section of a cct what affect will it have on the motor
Only affect motor starting
If contacts are added in the holding section of a cct what affect will it have o the motor
Running only motor can still bump
A motor on low voltage release will restart as soon as power is restored
True
In low voltage protection when power is reenergized motors auto restart
False
