Motor Contol Year 2 Flashcards
(41 cards)
What is another method for forward/reverse motors
Push button interlock (4 contact momentary push button)
What is the name for sudden reversal of direction in forward reverse motor
Plugging
What is dangerous jog cct
Where pressed too quickly the m coil stays energised and seals in even when job button released.
What drawing is best for troubleshooting
Schematic (most simplified drawing)
What drawing is best for wiring
Wiring diagram (label schematic with numbers first)
Limit switch
Has a lever which when pushed will open or close cct. Used to prevent over travel- doors etc.
Proximity switch
Sensor type limit switch - inductive and capacitive types and electronic
What is inductive proximity switch
Detect ferrous and non ferrous metals.
Traffic lights - have buried inductive coil car will drive on and increase magnetic field and change the current so light turns green. When drives away inductive coil will not be inducting and switch back to red
Capacitive proximity switch
Can detect any material places near it (close proximity) and change the state of switch
Photoelectric switch
Is a limit switch (photo eyes) uses laser beam and sensor
Thru beam
Reflective
Retro reflective
Types of thermal switches/thermostats
Bimetallic strip. Hard when normal state when heated it will droop and come into contact with contacts to change state
Remote bulb type-
As liquid in bulb expands due to heat it changes the state of the switch (used in freezers)
How does remote bulb temperature switch work
Bellows inside bulb expand and act as actuator and change state of switch
Two types of float switches
Cable float
Fixed float switch with high and low level floats
What do flow switches measure
Movement of liquid or gas
Uses a paddle which moves as fluid or gas moves changing state of switch
What do pressure switches measure
Pumps and air compressors
They are safety device to prevent to much pressure build up (cut in and cut out)
What is differential point on pressure switch
Difference between cut in and cut out
Air compressor cut in 105psi and cut out at 120psi =15psi differential
Three types of pressure switches
Bourbon type
Bellows
Diaphragm
Three types of time delay relays
Pneumatic
Motor driven
Electronic
On delay and off delay time delay relays difference
On delay - timing cycle begins when energised (DOE depend on energization)
Off delay - timing cycle begins when de-energised (DODE depends on de-energization)
What switch doesn’t include overload protection?
Drum switch
What is lockout relay
Built into zero speed switch to prevent switch working if not energised
What is anti plugging
To prevent a motor switching from forward/reverse whilst energised. Needs to come to a complete stop before changing direction - using zero speed switch
What is combination starter
Contains everything in power cct in same enclosure
