Motor Controll Flashcards
What is the disadvantage of a manual motor starter compared to a magnetic motor starter
No low-voltage protection
Only one location available for stopping/starting
Why must a single pull starting switch be connected in the “underground” circuit conductor
It will open up the hot to the motor if the contact is open or tripped the motor is at ground potential 
How would you reset a toggle type of manual starter that has tripped due to overload?
First turn completely to the off position, and then turn it back to the on position just like a circuit breaker
Describe manual motor control
Non-magnetic means push button or toggle switch
Describe automatic motor control
Using an electromagnetic starter with all of the controller benefits
What is the difference between overload protection and overcurrent protection?
Overload uses OL heat to protect the motor in the case of an overload
Overcurrent protects the whole circuit from grounds and shorts
What is the difference between low-voltage protection and low-voltage release?
LVR=2 wire control motor could reset automatically
LVP = three wire control requires a manual reset
What is a motor that uses low-voltage protection?
Lathes in the high school woodshop
What are motors that use low-voltage release?
Sump pump, ventilation, fan, air compressor
What is meant by “across the line” starting
The motor is connected to the full voltage of the source when starting
What is a combination starter?
Connecter with overload heaters, overcurrent, protection, fuse, circuit, breaker, and a disconnect
What does a power circuit have in it
(Power circuit) -disconnect, overcurrent protection, horsepower rated contacts, overload heater, motor branch circuit, conductors
What does a control circuit have in it?
(Control circuit) - overload contact control relay stop/start limit switches, auxiliary contacts
What is a schematic diagram?
Schematic shows the electrical relationships of the components
What is a wiring diagram?
It shows the physical location used to construct the circuit and how the connections are made
Why is it necessary for motor starters to be rated in horse power?
So they can handle the inrush current that is drawn when the motor is started
What is meant by the term normally closed and normally open
(Normally open contact) open in the de-energized state.
(Normally closed contact) - closed in denergized state
Why are magnetic starter? Contacts generally silver
Provide a lower resistant path
Doesn’t allow oxide to build up
Keeps contacts cooler
What parts of the magnetic starter are in the power circuit
Disconnect, overcurrent, device fuse/breaker main contacts, overload heaters, motor branch circuit wiring
What parts of the magnetic starter are in the control circuit
Overload contacts coil start/stop push button auxiliary contacts holding contacts limit switches
Why are some combinations starters provided with a door mechanical interlock?
So you cannot open them in the on position
What is the difference between a magnetic starter and a magnetic contactor
Starter has a connecter plus overload heaters
Why would you provide an overload relay to protect a motor circuit if the motor is already protected by a fuse?
It protects the motor overload conditions more precisely
What are two different types of thermal overload relays?
A) Bi-metallic
B) melting alloy/solder pot
What part of a thermal overload relay is in the power circuit
Heaters
What part of a thermal overload relay is in the control circuit
Close contact
Rather than overload, what conditions might cause the overload to trip?
High temperature loose connection, wrong heater selection
Why is the automatic reset overload used more then the manual reset type
It requires someone to physically check things out before resetting
List the events that describe the protection of a thermal over
Motor has an overload condition draws too much in power circuit, creating heat and overload heat either melts or bends solder pot/bi metallic strip, which will open the normally closed overload contact
State the effects of ambient temperature on a by metallic type of overload
If the temperature is too high, the bi metallic strip will be permanently bent
What do you have to do if the exact heater is not available for an overload relay?
Try to get one that is as close as possible and use a percent adjustment overload relay
What is the difference between a start pushbutton and a stop push button
Stop— normally closed and connected in series
Start—normally open and connected in parallel
How does a start push button actually start motor
When the start push button is pressed it energizes the coil, which then turns on the motor Contacts
What is two wire control?
Low-voltage release if no power it will restart
What is three wire control?
Low-voltage protection if no power, someone has to restart it
What is the seal in contact / holding contact
It is used to keep the magnetic starter energize until stopped
What is the normally open limit switch?
End of process
What is a close limit switch?
End of travel
What is it normally open push button
Start botton
What is it normally closed push button
Stop button
What is a Two position selector switch
Manually run and off
What is a three position selector switch?
Hand/off/auto application
What is a pilot light?
Run/stop overload blown indication
What does a holding or seal in contact
It keeps the motor running
