Chapter 1 electro mecha device part 4
-
Upload
hattori-sidek -
Category
Education
-
view
504 -
download
1
description
Transcript of Chapter 1 electro mecha device part 4
![Page 1: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/1.jpg)
D. Protection Circuit (Relays)
There are 4 types of protection circuit
–Diode circuit
–RC circuit
–Zeners circuit
–MOV circuit
![Page 2: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/2.jpg)
Different types of coil transient suppression
![Page 3: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/3.jpg)
Coil transient suppression..cont.
-When circuit complete (transistor forward bias), current will flow into relay coil & not through diode.-relay coil energize, produce magnetic field from i=0 to i=max.-but if transistor is off, circuit is open, current accumulate at relay coil need to discharge.-Will go through diode, called freewheeling diode.-But if no protection device, it will go back through relay coil and can cause arching (cause
contact to wear/oxidized).-strength of the i=max will slowly decay its value until i=0
-When circuit complete (transistor forward bias), current will flow into relay coil & not through diode.-relay coil energize, produce magnetic field from i=0 to i=max.-but if transistor is off, circuit is open, current accumulate at relay coil need to discharge.-Will go through diode, called freewheeling diode.-But if no protection device, it will go back through relay coil and can cause arching (cause
contact to wear/oxidized).-strength of the i=max will slowly decay its value until i=0
![Page 4: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/4.jpg)
Pressure switch
-Pressure is force exerted over a surface divided by its area ; P=F/A
-Pressure switch is control switch that detect amount of force & activates electrical contact when the set amount of force is reach.
-Application:To control the air pressure in the tank by turning the air compressor motor on whatever the tank pressure falls below the set value.
-Pressure is force exerted over a surface divided by its area ; P=F/A
-Pressure switch is control switch that detect amount of force & activates electrical contact when the set amount of force is reach.
-Application:To control the air pressure in the tank by turning the air compressor motor on whatever the tank pressure falls below the set value.
NC Pressure switch
NO Pressure switch
![Page 5: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/5.jpg)
Pressure switch application
-When switch is closed, current flows through rung 1, motor will start compress the air until system pressure is reach.-When system pressure is reach, the NC contact will open & pump motor is turn off.-When pressure in the compressor falls below the set point, pressure switch in rung 1 will close and restart the motor again.-NO contact use to signal overpressure condition.-Alarm is sound when overpressure.
![Page 6: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/6.jpg)
Example pressure switch.
-Deflecting mechanism that moves when a force (pressure) is applied
-Diaphragm switch use for pressure less than 200psi.
-Deflecting mechanism that moves when a force (pressure) is applied
-Diaphragm switch use for pressure less than 200psi.
Diaphragm
![Page 7: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/7.jpg)
Example pressure switch..cont.
-Cylindrical device with several deep fold which expand or contract when pressure is applied.-The expanding bellow
moves against spring mechanism which operate elect. contact when source pressure
increase.-can use for pressure up to 500psi.
-Cylindrical device with several deep fold which expand or contract when pressure is applied.-The expanding bellow
moves against spring mechanism which operate elect. contact when source pressure
increase.-can use for pressure up to 500psi.
Bellows
![Page 8: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/8.jpg)
Example pressure switch..cont.
-Move back & forth in a tight fitting chamber by pressure applied in a chamber.-Design for high pressure application of 10,000psi
-Move back & forth in a tight fitting chamber by pressure applied in a chamber.-Design for high pressure application of 10,000psi
Piston
![Page 9: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/9.jpg)
Limit Switch
-require physical contact of the object
with the switch actuator.
-the mechanical motion physically open or close a set of contact within the limit switch enclosure.
-require physical contact of the object
with the switch actuator.
-the mechanical motion physically open or close a set of contact within the limit switch enclosure.
NO limit switch
NC limit switch
![Page 10: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/10.jpg)
Reed Switch
-electrical switch operated by an applied magnetic field.- consists of pair of contact on ferrous metal reeds in a hermetically (insulated or protected from outside influences) sealed glass envelope.-contact maybe normally open, closing when magnetic field is present, or normally closed and opening when a magnetic field is applied -usage example-computer keyboards, petrol pump, automatic dentist drill activation.
![Page 11: Chapter 1 electro mecha device part 4](https://reader036.fdocuments.us/reader036/viewer/2022062511/54be58de4a7959bf048b4582/html5/thumbnails/11.jpg)
BREAK TIME !
Any Questions So far???
Thank you see u on next
story